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Andrea GATTO

Professore Ordinario
Dipartimento di Ingegneria "Enzo Ferrari"

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Pubblicazioni

- Procedimento per Migliorare la Resistenza all’Usura di Utensili in Composito Ceramico e Utensile ad Alta Resistenza all’Usura così Ottenuto [Brevetto]
L., Iuliano; Gatto, Andrea
abstract

La ricopertura con strati ceramici sottili di utensili per la tornitura di superleghe base Ni, aumentano il tempo di vita e i parametri di processo (velocità di taglio e avanzamento) di utensili per la tornitura di Inconel 718. La ricopertura di utensili in SiCw/Al2O3, selezionati come più idonei per la lavorazione di Inconel 718, rivestiti con riporti ceramici sottili in CrN e (Ti, Al)N, aumentano fino al 300% in termini di volume asportato il tempo di vita. Questo è imputabile non alla durezza, che presenta variazioni relativamente piccole rispetto al substrato, ma all'effetto barriera termica che il rivestimento esercita.

2023 - Beads for Cell Immobilization: Comparison of Alternative Additive Manufacturing Techniques [Articolo su rivista]
Gatto, M. L.; Mengucci, P.; Munteanu, D.; Nasini, R.; Tognoli, E.; Denti, L.; Gatto, A.
abstract

The attachment or entrapment of microbial cells and enzymes are promising solutions for various industrial applications. When the traps are beads, they are dispersed in a fluidized bed in a vessel where a pump guarantees fresh liquid inflow and waste outflow without washing out the cells. Scientific papers report numerous types of cell entrapment, but most of their applications remain at the laboratory level. In the present research, rigid polymer beads were manufactured by two different additive manufacturing (AM) techniques in order to verify the economy, reusability, and stability of the traps, with a view toward a straightforward industrial application. The proposed solutions allowed for overcoming some of the drawbacks of traditional manufacturing solutions, such as the limited mechanical stability of gel traps, and they guaranteed the possibility of producing parts of constant quality with purposely designed exchange surfaces, which are unfeasible when using conventional processes. AM proved to be a viable manufacturing solution for beads with complex shapes of two different size ranges. A deep insight into the production and characteristics of beads manufactured by AM is provided. The paper provides biotechnologists with a manufacturing perspective, and the results can be directly applied to transit from the laboratory to the industrial scale.

2023 - The Corrosion Behaviour of Additively Manufactured AlSi10Mg Parts Compared to Traditional Al Alloys [Articolo su rivista]
Gatto, Andrea; Cappelletti, Camilla; Defanti, Silvio; Fabbri, Fabrizio
abstract

Additive manufacturing of metal parts in the motorsport industry is becoming a decisive technology for producing lightweight and rigid parts, with increasing applications as the costs decrease. Among the available metal alloys, AlSi10Mg is one of the most widely used. In this paper, the corrosion resistance of additively manufactured AlSi10Mg is compared with that of other traditionally manufactured aluminium alloys widespread in the automotive industry. Several potentially corrosive agents, typical of vehicle applications, were used: salty water, motor oil, suspension oil, cooling fluid and gasoline. Corrosion tests were conducted at both room temperature and 90 C. The effects of heat and surface treatments were evaluated separately. The samples were visually inspected and weighed to evaluate the corrosion rate with the aid of SEM and EDS analysis. Additively manufactured AlSi10Mg generally showed better corrosion resistance in the stress-relieved condition as compared to the T6-treated state, with slightly better results for the polished samples. Motor oil, suspension oil, cooling fluid and gasoline did not significantly corrode the specimens, except for the T6-treated AlSi10Mg samples at 90 C. However, the corrosion rate was always higher than traditionally manufactured aluminium alloys tested for comparison.

2022 - A preliminary account of electro-chemical machining of Ti-48Al-2Nb-2Cr produced by electron beam melting [Relazione in Atti di Convegno]
Galati, M.; Defanti, S.; Vincenzi, N.; Marchiandi, G.; Gatto, A.; Iuliano, L.
abstract

2022 - Additive manufacturing process and product obtainable through the process [Brevetto]
Galati, Manuela; Bassoli, Elena; Gatto, Andrea; Iuliano, Luca
abstract

An additive manufacturing process for manufacturing a solid body (2) designed to be delimited by a predefined outer surface includes selecting at least one volume portion (6) of the solid body (2), preparing a three-dimensional model of the solid body (2) by means of a computer, in which the selected volume portion (6) is modelled independently of the rest of the solid body (2), supplying the model in a suitable data interface format to the processing unit of an additive manufacturing machine, and operating the additive manufacturing machine for producing the solid body (2) according to the model, thus obtaining the predefined outer surface.

2022 - An investigation on the processing conditions of Ti-6Al-2Sn-4Zr-2Mo by electron beam powder bed fusion: Microstructure, defect distribution, mechanical properties and dimensional accuracy [Articolo su rivista]
Galati, M.; Defanti, S.; Saboori, A.; Rizza, G.; Tognoli, E.; Vincenzi, N.; Gatto, A.; Iuliano, L.
abstract

2022 - Boosting Productivity of Laser Powder Bed Fusion for AlSi10Mg [Articolo su rivista]
Defanti, S; Cappelletti, C; Gatto, A; Tognoli, E; Fabbri, F
abstract

The Laser Powder Bed Fusion (L-PBF) process is recognized for high-end industrial applications due to its ability to produce parts with high geometric complexity. If lightweighting is one of the main strengths of L-PBF, a weakness is still the trade-off between high mechanical properties and competitive productivity. This objective can be targeted through a fine tuning of the process parameters within the manufacturing window. The paper pursues the combined optimization of part quality and process productivity for AlSi10Mg by going beyond the commonly used approach based solely on volumetric energy density. The effects of hatch distance and scan speed on the two targets were analyzed in detail. The best results were achieved by the adoption of a high scan speed and a low hatch distance, with notably different outcomes for nearly the same energy density.

2021 - Energy release as a parameter for fatigue design of additive manufactured metals [Articolo su rivista]
Santonocito, D.; Gatto, A.; Risitano, G.
abstract

Additive manufacturing (AM) is spreading in a wide range of industrial fields. The influence of the printing parameters on the mechanical performance is still an open issue among researchers, particularly when dealing with fatigue loads, which can lead to an unexpected failure. Classical fatigue tests require a large amount of time and materials to be consumed. Compared to the traditional fatigue assessment, the thermographic method (TM) is able to derive in a very rapid way the SN curve and fatigue limit of the material monitoring its energetic release during fatigue tests. In this work, for the first time, the energetic release during fatigue test has been evaluated in specimens made of AISI 316L, obtained by SLM technique. Compared to literature data, the specimens show premature failure, even at low stress levels, with brittle fracture surfaces. The internal microstructure seems to be strictly related to the energetic release of the material.

2020 - Development of a reliable method for contamination detection in raw metal powders for additive manufacturing [Relazione in Atti di Convegno]
Santecchia, E.; Mengucci, P.; Gatto, A.; Bassoli, E.; Denti, L.; Bondioli, F.; Barucca, G.
abstract

The evolution of additive manufacturing draws a growing attention to the quality of the raw materials involved. During Powder Bed Fusion (PBF), impurities can be trapped by the melting action of the laser or electron beam followed by a rapid solidification, resulting in discontinuities of the sintered products where failure is likely to start. To increase the quality of the sintered parts, it is mandatory to minimize the presence of impurities in the final product and therefore the risk of failure under service. This result can be achieved by improving the quality of the raw metal powders, which plays a key role in the overall process. In this study, intentionally contaminated AM metal powders were characterized by coupling scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) techniques with a statistical treatment of the data, obtaining a reliable method for powder impurities detection.

2020 - Effect of shot peening conditions on the fatigue life of additively manufactured A357.0 parts [Articolo su rivista]
Gatto, A.; Sola, A.; Tognoli, E.
abstract

Fatigue performance can be a critical attribute for the production of structural parts or components via additive manufacturing (AM). In comparison to the static tensile behavior of AM components, there is a lack of knowledge regarding the fatigue performance. The growing market demand for AM implies the need for more accurate fatigue investigations to account for dynamically loaded applications. A357.0 parts are processed by laser-based powder bed fusion (L-PBF) in order to evaluate the effect of surface finishing on fatigue behavior. The specimens are surface finished by shot peening using φ = 0.2 and φ = 0.4 mm steel particles and φ = 0.21-0.3 mm zirconia-based ceramic particles. The investigation proves that all the considered post-processing surface treatments increase the fatigue resistance of as-built parts, but the effect of peening with φ = 0.4 mm steel particles or with ceramic particles is more pronounced than that of peening with φ = 0.2 mm steel particles, although this treatment has the same Almen A value as the ceramic one. The surface morphology and the crack surface of the samples are also investigated.

2020 - Failure mechanism of silica coated polypropylene fibres for Fibre Reinforced Concrete (FRC) [Articolo su rivista]
Signorini, C.; Sola, A.; Malchiodi, Beatrice; Nobili, A.; Gatto, A.
abstract

This work investigates the effect of a fast, acid-catalysed sol-gel silica nano-coating on the mechanical performance of draw-wire Polypropylene (PP) fibres used as dispersed reinforcement in Fibre Reinforced Concrete (FRC). The failure mechanism is investigated. To this aim, the role of curing time is also considered. Mechanical performance is assessed in pull-out and three-point bending tests of un-notched beams. Coating deeply affects the post-cracking behaviour of FRC, which shifts from brittle (plain concrete), to softening (uncoated) and finally to plastic-softening (coated fibres). Remarkably, 28-day curing improves over 8-day curing in terms of energy dissipation capability for coated fibres only. This suggests that fibre-to-matrix bond enhancement moves the failure mechanism from delamination at the interface to failure in the interphase zone. In the former case, failure is inconsistent and occurs independently from the curing time while in the latter failure depends on the matrix quality.

2020 - Laser Powder Bed Fusion: Tailoring the microstructure of alloys for biomedical applications [Relazione in Atti di Convegno]
Santecchia, E.; Mengucci, P.; Gatto, A.; Bassoli, E.; Denti, L.; Rutkowski, B.; Barucca, G.
abstract

Additive manufacturing (AM) is particularly attractive for biomedical applications, where complex geometries and a high degree of individualization are required. Laser powder bed fusion (LPBF) is an AM technology exploiting the action of a solid-state laser to locally melt a metal powder according to a computer aided design (CAD) model. In the present study, the EOS Cobalt Chrome SP2 (Co-Cr-Mo-W) and Ti64 (Ti6Al4V) powders were sintered by the system equipped with a Yb fiber laser. During LPBF, the Co-Cr-Mo-W metal powder undergoes total melting followed by rapid cooling, giving rise to athermal martensitic phase transformation from the high-temperature ? (fcc) phase to the low-temperature ? (hcp) phase. This produces an intricate network of thin ?-lamellae inside the ? phase matrix. After the firing cycle this structure is maintained, and a massive presence of coarse precipitates is also observed. Owing to the rapid cooling taking place during LPBF, in Ti6Al4V sintered samples only the acicular martensitic a' phase is present. The firing cycle induces the ß phase formation at the a plate boundaries and this microstructure leads to reduced values of strength, with respect to those of the as-sintered samples. The highlighted behaviors show that by tuning the post-production heat treatments it is possible to tailor the microstructure and the mechanical properties.

2020 - Mesoscale modelling of laser powder-based directed energy deposition process [Relazione in Atti di Convegno]
Piscopo, G.; Atzeni, E.; Salmi, A.; Iuliano, L.; Gatto, A.; Marchiandi, G.; Balestrucci, A.
abstract

Laser Powder-based Directed Energy Deposition (LP-DED) process is a cutting-edge Additive Manufacturing (AM) technology for metal part repair and production. The disruptive potentialities of LP-DED are nowadays limited by the difficulty in the identification of the optimized set of process parameters, typically obtained from long and expensive experimental trials. In this work, a thermal simulation tool able to predict material deposition behaviour is developed using a finite element code. An original method is defined to model the material addition and energy flow. The forecasting capabilities of the model in terms of penetration depth and track dimensions are evaluated by comparing the numerical outcomes with experimental data.

2020 - Preliminary assessment of electro-chemical machining for aluminum parts produced by laser-based powder bed fusion [Articolo su rivista]
Defanti, S.; Denti, L.; Vincenzi, N.; Gatto, A.
abstract

Electro-chemical machining (ECM) is a nonconventional machining process based on the anodic dissolution of the workpiece. The peculiar features of this process make it suitable for application in the aerospace, automotive, or medical fields where laser-based powder bed fusion (L-PBF) is consolidating as a manufacturing solution for high-performance components. The roughness of as-built L-PBF parts often requires surface finishing before usage in order to enable a correct operation as well as to prevent early fatigue failure. The viability of ECM on L-PBF components is still scarcely investigated in the literature. In this article, the process was applied to AlSi10Mg parts produced by L-PBF. An experimental plan was designed to select the process parameters and to study their effect on the surface roughness and morphology. Process variables including feed rate, time, voltage, and water pressure were investigated. As a result, it was observed that the ECM performance was different for parts produced by traditional processes or by L-PBF, even for comparable composition. Owing to the presence of satellite particles on L-PBF surfaces, ECM was only effective in the pulsed mode.

2019 - Cross-contamination quantification in powders for additive manufacturing: A study on Ti-6Al-4V and maraging steel [Articolo su rivista]
Santecchia, E.; Mengucci, P.; Gatto, A.; Bassoli, E.; Defanti, S.; Barucca, G.
abstract

Metal additive manufacturing is now taking the lead over traditional manufacturing techniques in applications such as aerospace and biomedicine, which are characterized by low production volumes and high levels of customization. While fulfilling these requirements is the strength of metal additive manufacturing, respecting the tight tolerances typical of the mentioned applications is a harder task to accomplish. Powder bed fusion (PBF) is a class of additive manufacturing in which layers of metal powder are fused on top of each other by a high-energy beam (laser or electron beam) according to a computer-aided design (CAD) model. The quality of raw powders for PBF affects the mechanical properties of additively manufactured parts strongly, and therefore it is crucial to avoid the presence of any source of contamination, particularly cross-contamination. In this study, the identification and quantification of cross-contamination in powders of Ti-6Al-4V and maraging steel was performed using scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) techniques. Experimental results showed an overall good reliability of the developed method, opening the way for applications in machine learning environments.

2019 - Effect of Three Different Finishing Processes on the Surface Morphology and Fatigue Life of A357.0 Parts Produced by Laser‐Based Powder Bed Fusion [Articolo su rivista]
Gatto, Andrea; Bassoli, Elena; Denti, Lucia; Sola, Antonella; Tognoli, Emanuele; Comin, Andrea; Porro, Juan Antonio; Cordovilla, Francisco; Angulo, Ignacio; Ocaña, Jose Luis
abstract

A357.0 parts are processed by laser-based powder bed fusion and surface finished via plastic media blasting, ceramic sand blasting, and laser shock processing. The morphological analysis proves that plastic media blasting causes the most effective peak removal, the most efficient decrease in valley depth, and the greatest reduction in surface roughness. All the surface finishing processes enhance the fatigue life, however ceramic sand blasting bring about the greatest increase in the value of σmax for an infinite fatigue life limit of 2106 cycles. The experimental results suggest therefore that the infinite fatigue life value is more sensitive to the residual stress state engendered by ceramic sand blasting than to the reduction in surface roughness. Breakthrough cracks start at the interface between crushed or modified surface particles and the underlying macro-surface. However, at a distance of a few hundred microns from the crack initiation point, the fracture surface morphology become cellular for all the specimens.

2019 - Enhancing the quality of metal powder feedstock for laser PBF through cross-contamination removal [Relazione in Atti di Convegno]
Santecchia, E.; Mengucci, P.; Gatto, A.; Bassoli, E.; Denti, L.; Gheorghiu, B.; Barucca, G.
abstract

The presence of impurities in metal powder feedstock for laser powder bed fusion (L-PBF) can strongly affect the mechanical properties of the sintered part. As a matter of fact, the contamination particles trapped in the uniform metal matrix of the raw material, act as a discontinuity and, therefore, as a site for fatigue crack nucleation and growth, leading to a dramatic reduction of the expected fatigue life. While cross-contamination detection is a key parameter to establish the quality level of the metal powder feedstock, its removal is crucial to ensure that the sintered parts will fulfil the service requirements. In this study, metal powder feedstock for laser PBF were intentionally contaminated, submitted to a removal process based on their magnetic properties, through suitably developed equipment. The contaminated and processed powders were characterized by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) techniques.

2019 - Experimental approach to measure the restraining force in deep drawing by means of a versatile draw bead simulator [Articolo su rivista]
Bassoli, E.; Sola, A.; Denti, L.; Gatto, A.
abstract

The extreme personalization of the sports car industry requires the development of reliable and affordable techniques for the in-house set-up and control of processing conditions in deep drawing of body-in-white parts. In order to cope with this urgent need, a handy draw bead simulator (DBS) is proposed to measure the restraining force exerted on a sheet metal by the draw bead during deep drawing. The apparatus can be integrated into a common tensile testing machine and the male-female parts of the DBS are variable to account for different geometries of the draw bead and for different thicknesses of the sheet metal. For validation, the DBS is operated to reproduce the effect of a draw bead working on an Al6014-T4 strip according to assigned industrial conditions. Tensile tests repeated on the metal strip after drawing open the way to quantify work hardening effects. The new DBS can be applied to measure the restraining force and investigate the specific role of the draw bead in deep drawing, but it may also be used to verify the predictivity of computational models, thus supporting the development of simulations for feasibility studies and tool design optimization.

2019 - Fatigue life and microstructure of additive manufactured Ti6Al4V after different finishing processes [Articolo su rivista]
Denti, L.; Bassoli, E.; Gatto, A.; Santecchia, E.; Mengucci, P.
abstract

Finishing methods of additive manufactured metal parts are becoming a key driver of industrial viability, increasingly with additive processes being challenged in demanding end-product applications. The same scenario stresses the requirements as to fatigue life of parts built by Additive Manufacturing (AsM). The paper addresses fatigue life of Ti6Al4V produced by Powder Bed Fusion in four finishing conditions: as-built, tool machined, after tumbling and after tumbling and subsequent shot-peening. Failure mechanisms at the micro-scale are observed in order to reinforce the mechanical results by identifying the role of different surface morphologies in crack initiation. X-ray diffraction (XRD), scanning electron microscopy (SEM) techniques and microanalysis (EDX) are used to investigate microstructural modifications generated by the different finishing methods. Results show that tumbling alone does not improve fatigue life against the as built condition, whereas tumbling and subsequent shot peening allow matching the fatigue endurance of tool machined specimens. The shot peening process causes surface amorphization and implantation of the peening media turning into subsurface inclusions. Based on the results, an optimized finishing process can be envisaged, consisting in prolonged tumbling up to the removal of a stock allowance at least equal to the powder size, before shot peening.

2019 - Laser powder bed fusion: Tailoring the microstructure of alloys for biomedical applications [Relazione in Atti di Convegno]
Santecchia, E.; Mengucci, P.; Gatto, A.; Bassoli, E.; Denti, L.; Rutkowski, B.; Barucca, G.
abstract

Additive manufacturing (AM) is particularly attractive for biomedical applications, where complex geometries and a high degree of individualization are required. Laser powder bed fusion (LPBF) is an AM technology exploiting the action of a solid-state laser to locally melt a metal powder according to a computer aided design (CAD) model. In the present study, the EOS Cobalt Chrome SP2 (Co-Cr-Mo-W) and Ti64 (Ti6Al4V) powders were sintered by the system equipped with a Yb fiber laser. During LPBF, the Co-Cr-Mo-W metal powder undergoes total melting followed by rapid cooling, giving rise to athermal martensitic phase transformation from the high-temperature γ (fcc) phase to the low-temperature ε (hcp) phase. This produces an intricate network of thin ε-lamellae inside the γ phase matrix. After the firing cycle this structure is maintained, and a massive presence of coarse precipitates is also observed. Owing to the rapid cooling taking place during LPBF, in Ti6Al4V sintered samples only the acicular martensitic α' phase is present. The firing cycle induces the β phase formation at the α plate boundaries and this microstructure leads to reduced values of strength, with respect to those of the as-sintered samples. The highlighted behaviors show that by tuning the post-production heat treatments it is possible to tailor the microstructure and the mechanical properties.

2019 - Metastable Al–Si–Ni alloys for additive manufacturing: Structural stability and energy release during heating [Articolo su rivista]
Bedo, T.; Varga, B.; Cristea, D.; Nitoi, A.; Gatto, A.; Bassoli, E.; Bulai, G.; Velicu, I. -L.; Ghiuta, I.; Munteanu, S.; Pop, M. A.; Gabor, C.; Cosnita, M.; Parv, L.; Munteanu, D.
abstract

Rapid solidification with high cooling rates of metal alloys determines both the improvement of mechanical properties, due to the finishing of the structure, as well as obtaining metastable structures in the form of supersaturated or amorphous/nano solid solutions, which could potentially confer the material outstanding properties. It is of particular interest to use the energies released during the heating stage for these materials, due to the potentially lower input energy required to melt/fuse these materials. This phenomenon could add to the development and diversification of additive manufacturing technologies. The paper presents results concerning the structural development and phase transformation of metastable structures from Al–Si–Ni-based alloys, obtained by melt spinning and atomization techniques. It was observed that the structural transformations occurring during the heating process, starting from metastable structures, generate significant amounts of energy. This is of practical importance in the use of metallic powders in additive manufacturing technology, due to potentially reduced energy input.

2019 - Nanoscale characterization of metal alloys produced by laser powder bed fusion (LPBF) technology [Relazione in Atti di Convegno]
Gatto, A.; Rogante, M.; Santecchia, E.; Mengucci, P.
abstract

Advanced characterization at the nanoscale of Co-Cr-Mo-W, and Ti6Al4V alloys produced by Laser Powder Bed Fusion (LPBF) has been carried out in order to investigate the structural features responsible of the material performances. The alloys considered in this study are key materials in advanced field such as aerospace, automotive and biomedicine, while LPBF is becoming the reference for fabrication of metal parts by additive manufacturing (AM). Combining advanced metallic materials with innovative production technologies results in unexpected mechanical properties of final products. In this study, several characterization techniques including scanning (SEM) and transmission (TEM) electron microscopy, X-ray diffraction (XRD) and neutron-based techniques have been used to investigate the materials at the nanoscale.

2019 - Precipitates formation and evolution in a Co-based alloy produced by powder bed fusion [Articolo su rivista]
Santecchia, E.; Gatto, A.; Bassoli, E.; Denti, L.; Rutkowski, B.; Mengucci, P.; Barucca, Giulia
abstract

Metal additive manufacturing is strongly employed in aerospace and biomedical applications, whose high degree of customization and low production volumes are the main characteristics. Cobalt-based alloys have been widely used for dental prosthesis and can be produced via metal additive manufacturing, or rather powder bed fusion, in a more convenient way compared to traditional manufacturing techniques. In the present paper, a comprehensive study of the tight correlation between the microstructure and the static mechanical properties of Co-Cr-Mo-W samples produced by powder bed fusion, is reported. In particular, the formation of precipitates during the sintering process is observed, and the evolution of their size, shape and frequency due to post-processing and to a heat-treatment typical of dental applications, is exhaustively studied. By coupling different characterization techniques such as scanning transmission electron microscopy and small-angle neutron scattering, it was possible to correlate the ductility degradation of the samples with the formation and growth of coarse and elongated precipitates.

2019 - Solid-state phase transformations in thermally treated Ti-6Al-4V alloy fabricated via laser powder bed fusion [Articolo su rivista]
Mengucci, P.; Santecchia, E.; Gatto, A.; Bassoli, E.; Sola, A.; Sciancalepore, C.; Rutkowski, B.; Barucca, G.
abstract

Laser Powder Bed Fusion (LPBF) technology was used to produce samples based on the Ti-6Al-4V alloy for biomedical applications. Solid-state phase transformations induced by thermal treatments were studied by neutron diffraction (ND), X-ray diffraction (XRD), scanning transmission electron microscopy (STEM) and energy-dispersive spectroscopy (EDS). Although, ND analysis is rather uncommon in such studies, this technique allowed evidencing the presence of retained β in α' martensite of the as-produced (#AP) sample. The retained β was not detectable byXRDanalysis, nor by STEM observations. Martensite contains a high number of defects, mainly dislocations, that anneal during the thermal treatment. Element diffusion and partitioning are the main mechanisms in the α ↔ β transformation that causes lattice expansion during heating and determines the final shape and size of phases. The retained β phase plays a key role in the α' → β transformation kinetics.

2019 - Ti-Zr-Si-Nb nanocrystalline alloys and metallic glasses: Assessment on the structure, thermal stability, corrosion and mechanical properties [Articolo su rivista]
Gabor, C.; Cristea, D.; Velicu, I. -L.; Bedo, T.; Gatto, A.; Bassoli, E.; Varga, B.; Pop, M. A.; Geanta, V.; Stefanoiu, R.; Codescu, M. M.; Manta, E.; Patroi, D.; Florescu, M.; Munteanu, S. I.; Ghiuta, I.; Lupu, N.; Munteanu, D.
abstract

The development of novel Ti-based amorphous or β-phase nanostructured metallic materials could have significant benefits for implant applications, due to improved corrosion and mechanical characteristics (lower Young's modulus, better wear performance, improved fracture toughness) in comparison to the standardized α+β titanium alloys. Moreover, the devitrification phenomenon, occurring during heating, could contribute to lower input power during additive manufacturing technologies. Ti-based alloy ribbons were obtained by melt-spinning, considering the ultra-fast cooling rates this method can provide. The titanium alloys contain in various proportions Zr, Nb, and Si (Ti60Zr10Si15Nb15, Ti64Zr10Si15Nb11, Ti56Zr10Si15Nb19) in various proportions. These elements were chosen due to their reported biological safety, as in the case of Zr and Nb, and the metallic glass-forming ability and biocompatibility of Si. The morphology and chemical composition were analyzed by scanning electron microscopy and energy-dispersive X-ray spectroscopy, while the structural features (crystallinity, phase attribution after devitrification (after heat treatment)) were assessed by X-ray diffraction. Some of the mechanical properties (hardness, Young's modulus) were assessed by instrumented indentation. The thermal stability and crystallization temperatures were measured by differential thermal analysis. High-intensity exothermal peaks were observed during heating of melt-spun ribbons. The corrosion behavior was assessed by electrocorrosion tests. The results show the potential of these alloys to be used as materials for biomedical applications.

2019 - Weight reduction by topology optimization of an engine subframe mount, designed for additive manufacturing production [Relazione in Atti di Convegno]
Merulla, A.; Gatto, A.; Bassoli, E.; Munteanu, S. I.; Gheorghiu, B.; Pop, M. A.; Bedo, T.; Munteanu, D.
abstract

Additive Manufacturing (AM) technologies are getting more and more strategic for different purposes in many industrial fields. Among the most outstanding are part prototyping, single part to small batch production, relatively reduced manufacturing times and investments costs, reduced material consumption, and innovative and efficient shapes. The considerable advantages these technologies offer, compared to subtractive ones, make additive manufacturing a potentially industry-leading process in almost all domains - from aeronautics to the medical industry. Under these circumstances, the inspiration given by topology optimization tools can lead to feasible industrial parts, with fewer constraints in comparison to traditional manufacturing processes. The paper presents the development and the results obtained using topology optimization and design for AM technology on an automotive part: an engine mount sub-frame component for a rear middle engine sports car. The final design enables a significant weight reduction.

2018 - A Study on the Use of XCT and FEA to Predict the Elastic Behavior of Additively Manufactured Parts of Cylindrical Geometry [Articolo su rivista]
Esposito, F.; Gatto, A.; Bassoli, E.; Denti, L.
abstract

Defining general criteria for the acceptability of defects within industrial components is often complicated, since the specific load conditions and the criticality of the given application should be considered individually. In order to minimize the risk of failure, high safety factors are commonly adopted during quality control. However this practice is likely to cause the rejection of components whose defects would be instead acceptable if a more sound knowledge of the component behaviour were achieved. Parts produced by additive manufacturing (AM) may suffer from various defects, including micro- or macro-holes, delamination and microstructural discontinuities. Such processes, which are specially suitable for one-off components, require robust and reliable inspection before a part is accepted or rejected, since the refusal of even a single part at the end of the production process represents a significant loss. For this reason, it would be very useful to simulate in a reliable way whether a certain defect is truly detrimental to the proper working of the part during operation or whether the component can still be used, despite the presence of a defect. To this purpose, the paper highlights the benefits of a synergistic interaction between Industrial X-ray computed tomography (XCT) and finite element analysis (FEA). Internal defects of additively manufactured parts can be identified in a non-destructive way by means of XCT. Then FEA can be performed on the XCT-based virtual model of the real component, rather than on the ideal CAD geometry. A proof of concept of this approach is proposed here for a reference construct produced in an Aluminium alloy by AM. Numerical results of the proposed combined XCT–FEA procedure are contrasted with experimental data from tensile tests. The findings sustain the reliability of the method and allow to assess its full provisional accuracy for parts of cylindrical geometry designed to operate in the elastic field. The paper moves a step beyond the present application limits of tomography as it is currently employed for AM parts and it evidences instead the possibility of extending the usage of tomography to acceptance testing and prediction of operative behaviour.

2018 - Directed energy deposition of steel 316L: Effects of build orientation [Articolo su rivista]
Bassoli, Elena; Denti, Lucia; Gatto, Andrea; Sewell, Neil Thomas; Johns, Daniel
abstract

Metal Additive Manufacturing for the production of end parts is today the major interest in the field of layer-by-layer fabrication. Even if Powder Bed Fusion is by far the most diffused technology, powder-fed systems retain a specific attractiveness, mainly because they enable an easier manufacture of multi-material parts or even of composition-graded ones. These systems, recently categorized by ASTM standards under the term Directed Energy Deposition (DED), still suffer from scarce knowledge of part characteristics and of process robustness and repeatability. Among DED processes, Laser Consolidation (LC) allows the production of net-shape metal parts with good metallurgical soundness, high strength and ductility. As regards the mechanical performance, the non-coaxial architecture of the LC head poses the question of a secondary anisotropy, within each layer, in addition to the primary one that is due to the layerwise construction. The paper addresses the mechanical response and the microstructure obtained by LC with AISI 316L. The direction dependence of part properties is specifically explored. Remarkably high ductility, combined with high hardness and strength, are obtained. The effect of the relative orientation between the LC head and the part is quantified and associated with the observed microstructure.

2018 - Energy harvesting applied to smart shoes [Articolo su rivista]
Frontoni, Emanuele; Mancini, Adriano; Zingaretti, Primo; Gatto, Andrea
abstract

The appeal of energy harvesting systems lies in the possibility of capturing free energy that would be dissipated and is therefore obtainable without costs. Today, advanced techniques and devices exist for capturing from the environment, storing, and managing quotas of natural energy, which are made available in the form of electrical energy. At the same time, the most recent microprocessors grant an extremely high power efficiency, which permits their operation with minimal power consumption. As a consequence, low-consuming devices can be power supplied by using energy harvesting systems. If this concept is applied to wearable electronics, the most efficient choice is that of exploiting the energy released when the users walk, by developing systems that are embedded in the shoe sole. At each step, the force exerted on the device can be transformed into a relatively high amount of electrical energy, for example by using piezoelectric elements and electromagnetic induction systems. The paper describes the design of four different solutions for smart shoes that make use of energy harvesting apparatuses for the power supply of sensors and complex monitoring systems, for example aimed at GPS localization. An initial comparative assessment of the four architectures is reported, by weighing production costs, ease of manufacture and energy harvesting performance.

2018 - Experimental investigation and optimisation of laser direct part marking of Inconel 718 [Articolo su rivista]
Leone, C.; Bassoli, E.; Genna, S.; Gatto, A.
abstract

Many industries need product identification; laser marking is suitable to produce any kind of symbol, data matrix or bar code on parts. Consequently, the most important requirement for marking acceptance is, doubtless, the mark readability. The present study deals on the effect of process parameters on the laser marking of Inconel 718, with the aim to find a relation between the process parameters and mark characteristics in term of both mark geometry and readability. To this aim, laser markings, under different process conditions, were performed on Inconel 718 sheets, adopting a 30 W Q-switched Yb:YAG laser. The mark geometry was acquired by a 3D surface profiling system. Optical microscopy and SEM analysis were also performed on groove sections. In order to evaluate the readability of the marks, Weber contrast was calculated and adopted. The mark characteristics have been investigated by mean of statistical methodology (ANalysis of VAriance and Response Surface Method) and related to the process parameters. Furthermore, Master Response Optimisation methodology was adopted to individuate the optimal process conditions. It was found that mark geometry and the Weber contrast are mainly affected by the average power and the energy input per mark-length. Moreover, operative conditions allowing for maximum readability, yet without excessive increase in burr height, were also determined.

2018 - Molla elicoidale perfezionata [Brevetto]
Gatto, Andrea; Gatto, Francesco; Bassoli, Elena; Denti, Lucia
abstract

2018 - Repercussions of powder contamination on the fatigue life of additive manufactured maraging steel [Articolo su rivista]
Gatto, A.; Bassoli, E.; Denti, L.
abstract

A wide range of materials is suitable for processing by powder bed fusion (PBF) techniques. Among the latest formulations, maraging steel 18Ni-300, which is a martensite-hardenable alloy, is often used when both high fracture toughness and high strength are required, or if dimensional changes need to be minimised. In direct tooling, 18Ni-300 can be successfully employed in numerous applications, for example in the production of dies for injection moulding and for casting of aluminium alloys; moreover, it is particularly valuable for high-performance engineering parts. Even though bibliographic data are available on the effects that parameters, employed in PBF processes, have on the obtained density, roughness, hardness and microstructure of 18Ni-300, there is still a lack of knowledge on the fatigue life of PBF manufactured parts. This paper describes the fatigue behaviour of 18Ni-300 steel manufactured by PBF, as compared by forging. Relevant negative effects of the cross-contamination of the raw material are originally identified in this paper, which emphasizes the inadequacy of current acceptability protocols for PBF powders. In the absence of contamination, endurance achieved by PBF is found equal to that by forging and consistent with tooling requirements as set out by industrial partners, based on injection moulding process modelling.

2018 - Study of quality and composition of zinc anodes for cathodic ship protection [Relazione in Atti di Convegno]
Gatto, A.; Mengucci, P.; Rogante, M.; Grilli, F.
abstract

Quality and composition of the sacrificial zinc anodes are main issues in order to guarantee an efficient cathodic ship protection avoiding possible malfunctioning and failures. In the present study, sacrificial zinc anodes samples of different provenance and origins have been investigated, used for the galvanic protection of ships, and the composition has been identified able to guarantee satisfactory efficiency. This study concerns also the methodological approach to select and use one or more analysis techniques suitable for this purpose. Both traditional and advanced characterization techniques have been taken into account, actually, particularly useful for adequately interpreting chemical properties and other features of the considered materials.

2018 - The influence of powder particle and grain size on parts manufacturing by powder bed fusion [Relazione in Atti di Convegno]
Ghiuta, I.; Gatto, A.; Bassoli, E.; Munteanu, S. I.; Bedo, T.; Pop, M. A.; Gabor, C.; Covei, M.; Cosnita, M.; Cristea, D.; Varga, B.; Munteanu, D.
abstract

Nanostructured powder materials, or powders with increased amorphous ratio, can potentially lead to increased productivity during powder bed fusion, due to the hypothesis that nanostructured raw materials can be layer-sintered with lower specific energy, and consequently lower processing times when compared to commercial powders. Sintering of such materials can potentially be done faster, as compared to conventional powders. In addition, using nanostructured powders, or powders with high amorphous content, or even nanometric (nano-sized particles) powders, can result in higher density and hardness values of the sintered part, using the same process parameters. The main issue with nano-sized particles is their loss of flowability, which could be overcome by controlling the particle shape during manufacturing. This work presents our results concerning the manufacturing and characterization of titanium alloy powders, with potential use in additive manufacturing. The powders were manufactured using severe plastic deformation by mechanical milling from commercially available powders, with various rotation speeds, ball diameters, and milling periods, in order to obtain micrometric particles, but with nanometric or high amorphous content structures. The powders were further analyzed in terms of morphology, structure, and chemical composition.

2018 - Towards additive manufacturing of ramified scaffolds of the thyroid vascular system: A preliminary fractal analysis [Articolo su rivista]
Bassoli, E.; Denti, L.; Gatto, A.; Spaletta, G.; Sofroniou, M.; Parrilli, A.; Fini, M.; Giardino, Raffaele; SANDUZZI ZAMPARELLI, Alessandro; Zini, N.; Barbaro, F.; Bassi, E.; Mosca, S.; Dallatana, D.; Toni, R.
abstract

Fractal properties have been demonstrated in literature for several human vascular systems. In the frame of the investigation of additive manufacturing (AM) as a viable solution to prototype single arterial branches of human soft tissue organs, the paper provides a fractal analysis of the arterial tree of the human thyroid gland. The possibility that the thyroid arterial structure may be described as auto-similar is investigated, by studying injection-corrosion casts of the cadaveric gland. Vessel branching is analyzed by measuring branch diameters, ramification angles, and vessel lengths with the use of an optical microscope. Metrological results are made dimensionless by applying, as a scaling parameter, the caliber of major arteries. Data are then studied on a cumulative basis and processed to infer general rules for vessel branching. High resolution microtomography (mCT) is used to determine the spaces occupied by vascular branches and calculate their planar fractal dimension. Finally, the vascular tree has been simulated by a mixed, stochastic / deterministic algorithm based on diffusion limited aggregation (DLA), in which mean values of vascular variables are set as constraints. The purpose of this research is to understand if fractality can be reliably assumed for computational modeling of the organ anatomy, in order to be able to produce, by AM, more representative physical prototypes and scaffolds. The finding allow to affirm that the human thyroid arterial structure exhibits a degree of auto-similarity.

2018 - Use of an energy harvesting smart floor for indoor localization of people [Articolo su rivista]
Contigiani, Marco; Frontoni, Emanuele; Mancini, Adriano; Zingaretti, Primo; Gatto, Andrea; Groppo, Riccardo
abstract

The development of “intelligent” floors is a growing interest, but often the ensuing solutions involve high production costs as well as complicated installation and management. Aim of this paper is to propose a novel smart floor that makes use of an energy harvesting system in order to allow people localization and to track their movements in an indoor environment. The contribution starts from reviewing the state of the art of smart floor solutions, which are categorized according to the different applications they are addressed to. The system developed in this research is based on capacitive sensors that are mounted on a polymeric support and embedded between a bulk wooden base and floating parquet flooring. The paper outlines the detailed architecture of the proposed apparatus and reports the results of the preliminary test phase. The proposed solution is part of HDOMO, an Ambient Assisted Living (AAL) project aiming at the development of smart solutions for active aging.

2017 - DREAM: Driving up reliability and efficiency of additive manufacturing [Relazione in Atti di Convegno]
Sciancalepore, Corrado; Bondioli, Federica; Gatto, Andrea; Defanti, Silvio; Denti, Lucia; Bassoli, Elena
abstract

The DREAM project, financed by the EU Commission (H2020, Work program: FOF-13-2016: Photonics Laser-based production) is an end-user driven action which aligns the research and development of Additive Manufacturing (AM) technologies to the specific needs of its three industrial end users, Ferrari SpA, Adler Ortho France SARL, and RB Srl. The Action brings together experts in the field of AM technologies, powder and material characterization, component engineering, laser-matter interaction, to deliver an optimized approach that will be developed and demonstrated to the requirements of the end users. The first results of the project are here reported.

2017 - Dental Failure Analysis: The Need of a Comprehensive Failure Classification [Relazione in Atti di Convegno]
Gatto, Andrea; Iuliano, Luca; Atzeni, Eleonora; Minetola, Paolo; Salmi, Alessandro
abstract

For more than thirty percent of patients with implant-supported fixed dental prosthesis, various complications can be observed over five-years of function. In some cases, failure can be ascribed to mechanical reasons such as loosening of the retaining screws or fracture of the implant components. The paper evaluates three different failures of implant-supported prostheses. All cases were analyzed by optical and SEM microscopy to identify the failure modes and the possible failure causes. Improper design or errors in finishing operations or in assembly are identified as dental failure causes. A matrix classification is proposed to collect rupture cases of implant-supported prostheses.

2017 - Effects of build orientation and element partitioning on microstructure and mechanical properties of biomedical Ti-6Al-4V alloy produced by laser sintering [Articolo su rivista]
Mengucci, P.; Gatto, Andrea; Bassoli, Elena; Denti, Lucia; Fiori, F.; Girardin, E.; Bastianoni, P.; Rutkowski, B.; Czyrska Filemonowicz, A.; Barucca, G.
abstract

Direct Metal Laser Sintering (DMLS) technology was used to produce tensile and flexural samples based on the Ti-6Al-4V biomedical composition. Tensile samples were produced in three different orientations in order to investigate the effect of building direction on the mechanical behavior. On the other hand, flexural samples were submitted to thermal treatments to simulate the firing cycle commonly used to veneer metallic devices with ceramics in dental applications. Roughness and hardness measurements as well as tensile and flexural mechanical tests were performed to study the mechanical response of the alloy while X-ray diffraction (XRD), electron microscopy (SEM, TEM, STEM) techniques and microanalysis (EDX) were used to investigate sample microstructure. Results evidenced a difference in the mechanical response of tensile samples built in orthogonal directions. In terms of microstructure, samples not submitted to the firing cycle show a single phase acicular α’ (hcp) structure typical of metal parts subject to high cooling rates. After the firing cycle, samples show a reduction of hardness and strength due to the formation of laths of the β (bcc) phase at the boundaries of the primary formed α’ plates as well as to lattice parameters variation of the hcp phase. Element partitioning during the firing cycle gives rise to high concentration of V atoms (up to 20 wt%) at the plate boundaries where the β phase preferentially forms.

2017 - Reinforcement effectiveness on mechanical performances of composites obtained by powder bed fusion [Articolo su rivista]
Gatto, A.; Bassoli, E.; Denti, L.
abstract

New material formulations to be used in Additive Manufacturing machines are one of the major interests in this fast growing field. The possibility to tune functional and mechanical properties, by the addition of reinforcements to a polymeric matrix, is hindered by the low provisional capability of the additive manufactured composite. The inherent anisotropy of layer manufacturing combines with mechanisms of filler dispersion and of filler/matrix adhesion in a complex scenario. The paper entails a critical evaluation of mechanical properties measured for several polymeric composites produced by Powder Bed Fusion, in the perspective of provisional models commonly accepted for composite materials. The models are reviewed versus experimental and literature data. The provisional effectiveness is generally good, except for the case of nanometric or surface treated fillers, or of specific anisotropic microstructures obtained by layer manufacturing.

2016 - Bioartificial endocrine organs: At the cutting edge of translational research in endocrinology [Capitolo/Saggio]
Toni, R.; Bassi, E.; Barbaro, F.; Zini, N.; Zamparelli, A.; Alfieri, M.; Dallatana, D.; Mosca, S.; Della Casa, C.; Gnocchi, C.; Lippi, G.; Spaletta, G.; Bassoli, E.; Denti, L.; Gatto, A.; Ricci, F.; Tazzari, P. L.; Parrilli, A.; Fini, M.; Sandri, M.; Sprio, S.; Tampieri, A.
abstract

2016 - Biomedical Co-Cr-Mo Components Produced by Direct Metal Laser Sintering [Relazione in Atti di Convegno]
Girardin, E.; Barucca, G.; Mengucci, P.; Fiori, F.; Bassoli, E.; Gatto, A.; Iuliano, L.; Rutkowski, B.
abstract

Direct Metal Laser Sintering (DMLS) is an additive manufacturing technique based on a laser power source that sinters powdered materials using a 3D CAD model. The mechanical components produced by this procedure typically show higher residual porosity and poorer mechanical properties than those obtained by traditional manufacturing techniques. In this study, samples were produced by DMLS starting from a Co-Cr-Mo powder (in the γ phase) with a composition suitable for biomedical applications. Samples were submitted to hardness measurements and structural characterization. The samples showed a hardness value remarkably higher that those commonly obtained for the same cast or wrought alloys. In fact, the HRC value measured for the samples is 47 HRC, while the usual range for CAST Co-Cr-Mo is from 25 to 35 HRC. The samples microstructure was investigated by X-ray diffraction (XRD), electron microscopy (SEM and TEM) and energy dispersive microanalysis (EDX) in order to clarify the origin of this unexpected result. The laser treatment induced a melting of the metallic Co-Cr-Mo powder, generating a phase transformation from the γ (fcc) to the e (hcp) phase. The rapid cooling of the melted powder produced the formation of e (hcp) nano-lamellae inside the γ (fcc) phase. The nano-lamellae formed an intricate network responsible for the measured hardness increase. The results suggest possible innovative applications of the DMLS technique to the production of mechanical parts in the medical and dental fields, where a high degree of personalization is required.

2016 - Effects of thermal treatments on microstructure and mechanical properties of a Co-Cr-Mo-W biomedical alloy produced by laser sintering [Articolo su rivista]
Mengucci, P; Barucca, G.; Gatto, Andrea; Bassoli, Elena; Denti, Lucia; Fiori, F.; Girardin, E.; Bastianoni, P.; Rutkowski, B.; Czyrska Filemonowicz, A.
abstract

Direct Metal Laser Sintering (DMLS) technology based on a layer by layer production process was used to produce a Co-Cr-Mo-W alloy specifically developed for biomedical applications. The alloy mechanical response and microstructure were investigated in the as-sintered state and after post-production thermal treatments. Roughness and hardness measurements, and tensile and flexural tests were performed to study the mechanical response of the alloy while X-ray diffraction (XRD), electron microscopy (SEM, TEM, STEM) techniques and microanalysis (EDX) were used to investigate the microstructure in different conditions. Results showed an intricate network of ε-Co (hcp) lamellae in the γ-Co (fcc) matrix responsible of the high UTS and hardness values in the as-sintered state. Thermal treatments increase volume fraction of the ε-Co (hcp) martensite but slightly modify the average size of the lamellar structure. Nevertheless, thermal treatments are capable of producing a sensible increase in UTS and hardness and a strong reduction in ductility. These latter effects were mainly attributed to the massive precipitation of an hcp Co3(Mo,W)2Si phase and the contemporary formation of Si-rich inclusions.

2016 - Influence of electrode size and geometry in electro-discharge drilling of Inconel 718 [Articolo su rivista]
Bassoli, Elena; Denti, Lucia; Gatto, Andrea; Iuliano, Luca
abstract

Electro-discharge machining (EDM) of thin deep features widens processing opportunities of difficult-to-cut materials, such as Ni-based alloys, towards attractive industrial applications. Conversely, the complex interaction between electrical, thermal, and chemical phenomena in EDM thwarts process modeling and prediction. As a matter of fact, recent experimental discoveries encourage setting forth a new theory of discharge ignition in the gap, based on the role of debris, which lays foundations for a recursive mathematical model showing a chaotic evolution. The paper reports on electro-discharge drilling of small deep holes in Inconel 718. Process performances are measured with varying electrode size and geometry, attesting a pivotal effect of gap pollution on productivity and on the onset of a secondary detrimental removal of material by intergranular corrosion. All findings support the emerging model for discharge ignition via debris bridges, and, most notably, debris chains are documented for the first time in the field of metals, second only to a previous case for a ceramic composite. On the whole, the paper provides conclusive validation of the role of debris in the ignition of discharges.

2016 - On the behaviour of reinforcements beneath the surface in turning of metal-matrix composites (MMCs) [Articolo su rivista]
Gatto, Andrea; Iuliano, Luca; Atzeni, Eleonora; Minetola, Paolo; Salmi, Alessandro
abstract

A specific technical expertise is required to machine metal-matrix composites (MMCs). It is well known, from the literature data, that MMCs cutting involves high costs and high machining times due to excessive tool wear and possible subsurface damage. In recent years, the emphasis of research has focused on understanding the mechanics and mechanisms that are responsible for the behaviour of MMCs during the material removal process. These kinds of studies would be the most effective way of understanding the machining characteristics and deformation behaviour of the material. This work is a contribution to understanding the effects of two antagonistic phenomena that determine MMCs behaviour during the cutting process, such as the thermal softening of the matrix and the matrix hardening due to strain. To this end, a simplified model that describes the behaviour of the reinforcements beneath the machined surface is proposed and experimentally validated.

2015 - Energy harvesting smart floor for indoor people localization and tracking [Relazione in Atti di Convegno]
Gatto, Andrea; Bassoli, Elena; Contigiani, Marco; Frontoni, Emanuele; Mancini, Adriano; Zingaretti, Primo
abstract

The aim of this work is to describe an innovative smart floor based on a self powered system able to allow the localization and analysis of the movement of the users in a specific area. The solution presented involves the use of capacitive sensors on a polymeric support to be inserted between solid wood and a wooden part of a floating parquet. A detailed architecture and implementation of the smart floor is proposed together with an exhaustive test phase. In this paper we first describe the measurement system used to perform reliability and efficiency test of the system. Then the results are discussed and compared with the expected results and the performance of other solutions already known to the state of art. The proposed system is part of HDOMO, an Ambient Assisted Living (AAL) project aimed at developing smart solutions for active ageing.

2015 - Impact of additive manufacturing on engineering education – evidence from Italy [Articolo su rivista]
Minetola, Paolo; Iuliano, Luca; Bassoli, Elena; Gatto, Andrea
abstract

Purpose - The purpose of this paper is to evaluate how the direct access to additive manufacturing (AM) systems impacts on education of future mechanical engineers, within a Master's program at a top Italian University. Design/methodology/approach - A survey is specifically designed to assess the relevance of entry-level AM within the learning environment, as a tool for project development. The survey is distributed anonymously to three consecutive cohorts of students who attended the course of "computer-aided production (CAP)", within the Master of Science Degree in Mechanical Engineering at Politecnico di Torino. The course includes a practical project, consisting in the design of a polymeric product with multiple components and ending with the production of an assembled prototype. The working assembly is fabricated by the students themselves, who operate a fused deposition modelling (FDM) machine, finish the parts and evaluate assemblability and functionality. The post-course survey covers diverse aspects of the learning process, such as: motivation, knowledge acquisition, new abilities and team-working skills. Responses are analyzed to evaluate students' perception of the usefulness of additive technologies in learning product design and development. Among the projects, one representative case study is selected and discussed. Findings - Results of the research affirm a positive relationship of access to AM devices to perceived interest, motivation and ease of learning of mechanical engineering. Entry-level additive technologies offer a hands-on experience within academia, fostering the acquisition of technical knowledge. Research limitations/implications - The survey is distributed to more than 200 students to cover the full population of the CAP course over three academic years. The year the students participated in the CAP course is not tracked because the instructor was the same and there were no administrative differences. For this reason, the survey administration might be a limitation of the current study. In addition to this, no gender distinction is made because historically, the percentage of female students in Mechanical Engineering courses is about 10 per cent or lower. Although the answers to the survey are anonymous, only 37 per cent of the students gave a feedback. Thus, on the one hand, impact assessment is limited to a sample of about one-third of the complete population, but, on the other hand, the anonymity ensures randomization in the sample selection. Practical implications - Early exposure of forthcoming designers to AM tools can turn into a "think-additive" approach to product design, that is a groundbreaking conception of geometries and product functionalities, leading to the full exploitation of the possibilities offered by additive technologies. Social implications - Shared knowledge can act as a springboard for mass adoption of AM processes. Originality/value - The advantages of adopting AM technologies at different levels of education, for diverse educational purposes and disciplines, are well assessed in the literature. The innovative aspect of this paper is that the impact of AM is evaluated through a feedback coming directly from mechanical engineering students.

2015 - Multi-disciplinary approach in engineering education: learning with additive manufacturing and reverse engineering [Articolo su rivista]
Gatto, Andrea; Bassoli, Elena; Denti, Lucia; Iuliano, Luca; Minetola, Paolo
abstract

Purpose - The purpose of this paper is to report an interdisciplinary, cooperative-learning project in a second-year course within the "Enzo Ferrari" Master of Science Degree in Mechanical Engineering. The work aims to raise awareness of the educational impact of additive manufacturing and reverse engineering. Design/methodology/approach - Students are asked to develop, concurrently, the design and the manufacturing solution for an eye-tracker head mount. A digital head model is reverse engineered from an anatomical mannequin and used as an ergonomic mock-up. The project includes prototype testing and cost analysis. The device is produced using additive manufacturing techniques for hands-on evaluation by the students. Findings - Results of the presented case study substantiate the authors' belief in the tremendous potential of interdisciplinary project-based learning, relying on innovative technologies to encourage collaboration, motivation and dynamism. Originality/value - The paper confirms a spreading conviction that the soon-to-be engineers will need new practice-oriented capabilities to cope with new competitive scenarios. Engineering education must adapt to the social, rather than industrial, revolution that is being brought about by additive fabrication.

2015 - On the chaotic nature of electro-discharge machining [Articolo su rivista]
Gatto, Andrea; Sofroniou, Mark; Spaletta, Giulia; Bassoli, Elena
abstract

The long-accepted thermoelectric model for electro-discharge machining is being brought into question. Several experimental facts prompt the proposal of a new theory based on the effect of gap pollution on the ignition of discharges. The first experimental proof comes from the recently reported observation of debris chains and clusters. In this view, each step of the process depends on the previous ones through a deterministic relation, even if the overall evolution is unpredictable. The paper establishes mathematical grounds for the abovementioned intuitions by setting up and solving a recursive equation for the machining energy employed at each discharge event. By means of numerical and algebraic tools, the above equation is studied and shows a chaotic evolution similar to that of the logistic map. Results reconcile the apparent paradox between deterministic nature and stochastic localization of the discharges and introduce a description of the chaotic dynamics of electro-discharge processes.

2015 - Structural characterization of biomedical Co-Cr-Mo components produced by direct metal laser sintering [Articolo su rivista]
Barucca, G.; Santecchia, E.; Majni, G.; Girardin, E.; Bassoli, Elena; Denti, Lucia; Gatto, Andrea; Iuliano, L.; Moskalewicz, T.; Mengucci, P.
abstract

Direct metal laser sintering (DMLS) is a technique to manufacture complex functional mechanical parts from a computer-aided design (CAD) model. Usually, the mechanical components produced by this procedure show higher residual porosity and poorer mechanical properties than those obtained by conventional manufacturing techniques. In this work, a Co-Cr-Mo alloy produced by DMLS with a composition suitable for biomedical applications was submitted to hardness measurements and structural characterization. The alloy showed a hardness value remarkably higher than those commonly obtained for the same cast or wrought alloys. In order to clarify the origin of this unexpected result, the sample microstructure was investigated by X-ray diffraction (XRD), electron microscopy (SEM and TEM) and energy dispersive microanalysis (EDX). For the first time, a homogeneous microstructure comprised of an intricate network of thin ε (hcp)-lamellae distributed inside a γ (fcc) phase was observed. The ε-lamellae grown on the {111}γ planes limit the dislocation slip inside the γ (fcc) phase, causing the measured hardness increase. The results suggest possible innovative applications of the DMLS technique to the production of mechanical parts in the medical and dental fields.

2015 - Surface and sub surface evaluation in coated-wire electrical discharge machining (WEDM) of INCONEL® alloy 718 [Relazione in Atti di Convegno]
Atzeni, E.; Bassoli, E.; Gatto, A.; Iuliano, L.; Minetola, P.; Salmi, A.
abstract

Wire Electncal Discharge Machining (WEDM) is one of the most versatile and useflil technological processes for cuttmg complex shapes made of conductive matenals such as those typical of aerospace applications. With the aim to optimize process parameters, this paper studies the surface and subsurface modifications of INCONEL® alloy 718 (UNS N077 18) machined by WEDM using a Zinc coated brass wire. Machining was perfomwd under roughing and finishing conditions by setting different values of discharge energy and wire feed rate. Surface roughness of the cut surfaces was measured as well as the micro-hardness profile on polished sections. WED-machined surfaces and their cross sections were also observed by Scannmg Electron Microscope (SEM) and analyzed by Energy Dispersive X-ray Spectroscopy (EDS) to evaluate possible vanations of the surface chemical composition. In this investigation, results are discussed as a ifinction of the feed rate and of the smgle pulse discharge energy, which is determined by duration, peak current and discharge voltage of the discharge pulse. The research demonstrates that the required surface roughness can be achieved by properly settmg the feed rate and the smgle pulse discharge energy on the WEDM machme. Expenmental results also show that under the re-melted layer thickness no significant white layer formation or thermal modification occur, indicatmg that the chosen set of operatmg parameters minimizes secondary and unwanted chemical reactions.

2015 - Tolerance analysis for cast vs machined dental implants [Relazione in Atti di Convegno]
Atzeni, E.; Bassoli, E.; Denti, L.; Gatto, A.; Iuliano, L.; Minetola, P.; Salmi, A.
abstract

The paper addresses the dimensional tolerance and assembly accuracy of prosthetic components obtained by different manufacturing processes. The success of single tooth implant replacements hangs on the stability of the hexagonal connection, but no standard control procedures are available for its evaluation. The research aims at proposing a new protocol for the dimensional assessment of implant-Abutment connections, based on non-contact measurement and statistical data processing. The procedure is applied to machined-And cast-on abutments, as well of the matching implants. Samples are measured using an optical measuring microscope and data are processed to obtain the international tolerance (IT) grade. The rotational misfit is then calculated using the apothems of the external and the internal hexagon. As to the results, all the components are classified between IT8 and IT9 and the maximum rotational misfit is around 4 for all the assemblies, inferior to the critical limits for the screw joint stability. An objective dimensional characterization of prosthetic components and assemblies is reported, which is the basis for their reliability in clinical applications. From a wider perspective, an original measuring protocol is proposed, independent of parts assembly and based on international tolerances.

2014 - A planar fractal analysis of the arterial tree of the human thyroid gland: implications for additive manufacturing of 3D ramified scaffolds. [Relazione in Atti di Convegno]
Bassoli, Elena; Denti, Lucia; Gatto, Andrea; G., Spaletta; M., Sofroniou; A., Parrilli; M., Fini; R., Giardino; A., Zamparelli; N., Zini; F., Barbaro; E., Bassi; S., Mosca; D., Dallatana; R., Toni
abstract

It is currently known that a number of human vascular systems have a fractal geometry. Since we have recently developed a technique to prototype single arterial branches of human soft tissue organs by additive layer manufacturing (AM), we have explored the possibility that auto-similarity in vessel branching represents a key variable for accurate computational modeling of the organ three-dimensional (3D) macro / microscopic anatomy, and its reproduction by inverse engineering. To this purpose, ramification features of the intralobar arteries of the human thyroid were studied using injection-corrosion casts of the cadaveric gland. Vessel diameters, ramification angles, and branch lengths were measured by light microscopic, computer-aided optical metrology. Distribution of morphological variables was considered on a cumulative basis, and special focus was given to the branching laws. To reduce the bias of vascular distortion due to the pressure of intravascular resin injection, measures were made dimensionless through the use of a scaling parameter set on the vascular caliber of major afferent arteries. In addition, using high resolution microtomography (mCT) equipped with CTAn software and the Otsu algorithm for segmentation, spaces occupied by vascular branches (referred to as Volume of Interest, VOI) were selected, and their planar fractal dimension calculated. Finally, a computational simulation of the vascular tree was achieved using a mixed, stochastic / deterministic algorithm based on diffusion limited aggregation (DLA), constrained by mean values of vascular variables. Ratios among decreasing cast calibers, ramification angles, and branch lengths, respectively, were found strictly interrelated, mCT-VOI depicted fractal dimensions, and DLA simulation led to a fractal-like organization consistent with real data morphometrics. In summary, thyroid arterial geometry reliably exhibited a degree of auto-similarity, suggesting that fractality is a key feature for computational modeling and eventual AM of 3D vascular networks of the human thyroid.

2014 - Additive manufacturing as a cost-effective way to produce metal parts [Relazione in Atti di Convegno]
Atzeni, E.; Iuliano, L.; Marchiandi, G.; Minetola, P.; Salmi, A.; Bassoli, E.; Denti, L.; Gatto, A.
abstract

Recent developments in additive manufacturing technologies for the production of metal parts make this processes very attractive to high technology industries. Especially the geometrical freedom allow to produce components optimized for their functionality, disregarding limitations imposed by the manufacturing process. However, production costs should be evaluated to assess the convenience of additive manufacturing (AM) with respect to traditional technologies. Thus in this paper a break-even analysis is described, comparing the Selective Laser Melting (SLM) additive process with High Pressure Die Casting (HPDC) and 5-axis machining. Costs models are discussed for each process and benefits of applying redesign for additive manufacturing are illustrated. An aeronautical component is selected as case study to estimate the production volume for which additive manufacturing is cost-effective. The study proves the economical convenience of additive manufacturing with respect to traditional technologies from prototypes to small batch production. © 2014 Taylor & Francis Group.

2014 - Electro-Discharge Drilling on DMLS parts in Co-Cr-Mo alloy [Relazione in Atti di Convegno]
Gatto, Andrea; Bassoli, Elena; Denti, Lucia; E., Atzeni; L., Iuliano; G., Marchiandi; P., Minetola; A., Salmi; F., Calignano
abstract

Cobalt-base alloys are generally used in applications that require wear, corrosion and heat resistance. In particular, Cobalt-Chromium-Molybdenum (Co-Cr-Mo) alloy is adopted in the aerospace and medical field. These applications are characterized by low volumes and high personalization, so they could take advantage by the employment of additive technologies, such as Direct Metal Laser Sintering (DMLS). This technology still has limitations for the manufacture of small cavities, such as holes with diameters below 0.6mm and high aspect ratio, which require drilling of the additive manufactured part. Scope of this research is to investigate the effects of Electro-Dicharge Drilling (EDD) on surface and subsurface features of CoCrMo samples built by DMLS. High aspect ratio holes are produced with diameter of 0.6 mm and depth fifteen times higher. The attractiveness of ED machining for thin deep geometries stems from then absence of physical contact between tool and workpiece, which makes machining forces negligible and minimizes tool deformation. Micro features can be produced with a high accuracy irrespective of the material hardness and strength. Material Removal Rate (MRR), Electrode Wear (EW) and surface roughness are investigated versus the process parameters. Results are supported by the study of material removal mechanisms and surface morphology in the microscale, to account for the macroscopic trends.

2014 - Energy Harvesting system for smart shoes [Relazione in Atti di Convegno]
Gatto, Andrea; Frontoni, E.
abstract

The aim of Energy Harvesting is to capture free energy, available without costs, from the environment. The development of advanced techniques allowed to capture, to store and to manage amounts of natural energy, transforming them into electrical energy. Moreover, advancements in microprocessor technology have increased power efficiency, effectively reducing power consumption requirements. From the point of view of wearable electronics devices, the most efficient Energy Harvesting system for energy capturing is that to use devices inserted into the shoes. These devices are situated into the soles where, during the movement, a force is exerted. Using piezoelectric elements and electromagnetic induction systems, this force allows recovering a high quantity of electrical energy useful for sensor supply and complex monitoring systems. In this paper, four different solutions of smart shoes that use Energy Harvesting systems are presented, with the aim to recover energy to supply a GPS device. Preliminary comparative results of 4 different solutions are compared on the bases of costs, production feasibility and energy harvesting capabilities.

2014 - Indoor people localization and tracking using an energy harvesting smart floor [Relazione in Atti di Convegno]
Gatto, Andrea; Frontoni, E.; Mancini, A.; Contigiani, M.
abstract

In the recent years, different kind of intelligent floors have been proposed but they are expensive and in many cases difficult to install and manage. In this paper, we previously describe the state of the art concerning smart floors designed to satisfy different applications and then we present an intelligent floor realized for localizing and tracking people in an indoor environment. The aim of this work is to propose an innovative smart floor based on an energy harvesting system able to allow the localization and analysis of the movement of the users in a specific space. The solution presented in this paper involves the use of capacitive sensors on a polymeric support to insert between solid wood and a wooden part of a floating parquet. The proposed system is part of HDOMO, an Ambient Assisted Living (AAL) project developing smart solutions for active aging. A detailed architecture of the smart floor is proposed together with a preliminary test phase.

2014 - On the Effect of Electrodischarge Drilling on the Fatigue Life of Inconel 718 [Relazione in Atti di Convegno]
Bassoli, Elena; Baldini, Andrea; Gatto, Andrea; Strozzi, Antonio; Denti, Lucia
abstract

Difficult-to cut-materials are associated with premature tool failure, most likely in the case of complex geometries and this shapes. However, Nickel-based alloys are commonly used in high-temperature and aerospace applications, where thin deep holes are often required. Then, the only viable manufacturing solution relies on non-contact processes, like electrodischarge (ED) drilling. Morphology of ED machined surfaces is significantly different than obtained by metal-cutting operation and is known to jeopardize fatigue strength, but the extent needs to be gauged and related to the process parameters. Aim of the paper is to study the effect of holes (0.8 mm diameter, aspect ratio 10) produced by ED drilling on the fatigue life of Inconel 718. Rotating bending fatigue tests are carried out on specimens drilled under two ED setups, as well as with a traditional cutting tool. Specimens free from holes are fatigued under the same conditions for comparison. Based on previous studies, extremal ED parameters are selected, giving best surface finish versus highest productivity. S-N curves show that the ED process causes a decrease of the fatigue resistance with respect to traditional drilling, whereas the effect of different ED setups is negligible. Maximum productivity can thus be pursued with no threat to fatigue performance. The fatigue limit variation is quantified by using the superposition effect principle: ED drilling causes an increase of the stress concentration factor around 25% if compared to traditional drilling. The macroscopic fatigue behavior is integrated with a study of the effects of the different drilling processes in the micro-scale, by means of a microstructural and fractographic analysis.

2013 - Bridges of debris in the edd process: going beyond the thermo-electrical model [Articolo su rivista]
Gatto, Andrea; Bassoli, Elena; Denti, Lucia; Iuliano, L.
abstract

Electro-Discharge (ED) processes depend on the contemporaneous effect of many factors, which complicates process control/predictability and induced many authors in the last 60 years to work on explicative models. Studies split into two main approaches: theoretical and empirical. Theoretical works are based on the thermo-electrical theory and try to describe process phenomena by a physical model, with unavoidable assumptions and simplifications that cause a move away from veracity. On the contrary, experimentalists establish empirical models based on statistical analysis of results and optimization methods, but the findings are limited to domain-specific applications. In addition, numerous papers focus on single-spark analysis, failing in considering the interaction between successive discharges, or of transient phenomena as the presence of bubbles and debris in the gap. At present the scientific debate involves the ignition model, with two different points of view regarding the discharge-driving phenomenon: the debris bridge effect (pollutants in the dielectric drive the performances), and the dielectric strength effect (properties of the dielectric drive the performances). The paper addresses this dispute by investigating the debris formed during small-hole ED drilling of a 72 wt% Al2O3 - 28 wt% TiC composite. Particles are found to hollow out and pack within the gap, joining by necks. The first experimental evidence is given of the presence of chains and clusters of debris, towards a new model for electrodischarge processes that goes beyond the thermoelectric theory.

2013 - Energy harvesting for smart shoes: A real life application [Relazione in Atti di Convegno]
Frontoni, Emanuele; Mancini, Adriano; Zingaretti, Primo; Gatto, Andrea
abstract

Advanced technical developments have increased the efficiency of devices in capturing trace amounts of energy from the environment (such as from human movements) and transforming them into electrical energy (e.g., to instantly charge mobile devices). In addition, advancements in microprocessor technology have increased power efficiency, effectively reducing power consumption requirements. In combination, these developments have sparked interest in the engineering community to develop more and more applications that utilize energy harvesting for power. The approach here described aims to designing and manufacturing an innovative easy-to-use and general-purpose device for energy harvesting in general purpose shoes. The novelty of this device is the integration of polymer and ceramic piezomaterials accomplished by injection molding. In this spirit, this paper examines different devices that can be built into a shoe, (where excess energy is readily harvested) and used for generating electrical power while walking. A Main purpose is the development of an indoor localization system embedded in shoes that periodically broadcasts a digital RFID as the bearer walks. Results are encouraging and real life test are conducted on the first series of prototypes. Copyright © 2013 by ASME.

2013 - Investigation into the failure of Inconel exhaust collector produced by laser consolidation [Articolo su rivista]
Bassoli, Elena; Neil, Sewell; Denti, Lucia; Gatto, Andrea
abstract

Among layer manufacturing techniques, Laser Consolidation (LC) finds its ideal application in the production of thin-walled metal parts for industrial niches characterised by high innovation and product complexity. To fully exploit the technological potential, developments must be made to assess LC’s repeatability and reliability. Previous studies proved that high strength parts of fine microstructure are obtained if appropriate build strategies are used. The aim of this research is to analyse a racecar exhaust collector, built in Inconel by LC, relating the failure modes and microstructure to the construction plan. The exhaust collector component was built using a custom strategy and was run on a dynamometer before failing after approximately 1200 km. An investigation of the failure mechanism was carried out by a primary macroscopic analysis, aided by an X-ray control and dye penetrant test. Metallographic sections were then sampled from the critical areas to study the microstructure and relate it to the manufacturing process. Results proved that the distribution of primary microcracks associated with internal residual stresses caused by the build strategy and aggravated by differential shrinkage during the test thermocycles was responsible for ultimate failure. This issue was a result of build strategy and the non-coaxial laser head, therefore, alternative pathways could be developed capable of removing most, if not all, of the contributory factors. The analysed case suggests that LC build strategy selection is as critical to ensure low cycle fatigue resistance as component design and confirms that LC is effective in the production of advanced technological parts with high geometrical complexity given the correct build strategy.

2013 - Studies on electro discharge drilling of an Al2O3 –TiC composite [Articolo su rivista]
F., Calignano; Denti, Lucia; Bassoli, Elena; Gatto, Andrea; L., Iuliano
abstract

Ceramic matrix composites (CMCs) can be attractive for structural applications, but their machining by conventional methods is expensive and often critical. Complex geometries on advanced ceramics require contactless processes, such as electro discharge machining (EDM) or -drilling (EDD). These proved to be viable for CMCs with electrical resistivity below a critical value in the range of 1-3 Ωm. The condition is complied with by many CMCs: an example is alumina with titanium carbide. Material removal of ceramics by electrical discharges is a complex process involving different mechanisms, depending on the process setup. The paper describes an experimental study on EDD of 0.4 mm diameter holes with aspect ratio of 20 in Al2O3-TiC, using copper electrodes. Peak current (Ip), pulse-on time (ton) and pulse-off time (toff) are varied as independent variables. Four performance indicators are measured: material removal rate (MRR), electrode wear rate (EWrate), overcut (OC) and surface roughness (Ra, Sa). Empirical models are proposed to describe t the effect of process parameters on the output indicators. The analysis is supported by the observation of the surface and subsurface morphology, with the aim of investigating the material removal mechanisms and attaining a full comprehension of macroscopic results. It is found that removal mostly occurs by melting and evaporation and that surface morphology is determined by two phenomena ruled by pulse power. A process description is proposed, built around power as the ruling factor.

2012 - A combined Additive Layer Manufacturing / Indirect Replication method to prototype 3D vascular-like structures of soft tissue and endocrine organs [Articolo su rivista]
Bassoli, Elena; Denti, Lucia; Gatto, Andrea; G., Spaletta; A., Paderno; N., Zini; A., Parrilli; R., Giardino; V., Strusi; D., Dallatana; S., Mastrogiacomo; A., Zamparelli; M., Iafisco; R., Toni
abstract

We describe an innovative methodology combining Additive Layer Manufacturing and indirect replication to reconstruct reticular-like, three-dimensional structures mimicking the vascular network of soft tissue and endocrine organs. Using a fractal-like algorithm capable of modeling the intraparenchymal vascular distribution of these viscera, single intraglandular branches of the human thyroid arteries were prototyped with synthetic resin, based on the algorithmic STL output and ALM techniques. Satisfactory dimensional accuracy was obtained for these models, which were used as masters to evaluate protocols for their indirect replication, through both single and double procedures. Additional studies were conducted using casts of the human kidney arteries, obtained by injection / corrosion of the isolated organ. Satisfactory 3D reproduction of the external morphology of the kidney vessels was achieved. We conclude that our approach has the potential to develop up to the reconstruction with biomaterials of an entire, intraparenchymal vascular tree of soft tissue and endocrine organs.

2012 - Bioengineering of the thyroid lobe: use of its stromal / vascular matrix as a scaffold for ex situ reconstruction [Abstract in Atti di Convegno]
Toni, R.; Strusi, V.; Zini, N.; Dallatana, D.; Mastrogiacomo, S.; Parrilli, A.; Giardino, R.; Lippi, G.; Spaletta, G.; Bassoli, Elena; Gatto, Andrea; Iafisco, M.; Sandri, M.; Tampieri, A.
abstract

Regenerative medicine of endocrine glands is one of the newest fields in biomedical research, and promises to become a primary strategy to treat a number of endocrine disorders. Using computational bioengineering we have recently suggested that the threedimensional (3D) geometry of the thyroid, stromal / vascular matrix may act as an epigenetic guidance for growth and differentiation of developing thyrocytes (1-3). To test this hypothesis, we have bioengineered ex situ (i.e. on the laboratory bench) a bioartificial rat thyroid lobe using its decellularized stromal/vascular matrix as a natural 3D scaffold, to be eventually recellularized with thyroid stem/precursor cells. Sprague-Dawley male rats (125- 225 g) were used as thyroid donors, and lobe matrixes were prepared using a N 2 freezing / Trypsin-EDTA / Triton-deoxycholate processing. Test matrixes were made electrondense, and analyzed by microTC (Skyscan 1172) to define their architecture. Primary thyroid cells were isolated after 72 h in primary monolayer culture, whereas presence of ABCG2-positive stem/precursor elements was determined using Western blotting. Following trypsinization, 250 - 450 x 103 cells were harvested and dropped onto the empty follicular cavities of the inner matrix of single lobe halves for homing . Cultures were kept in static conditions up to 14 days. The recellularized matrixes were either fixed in aldheydes and analyzed with light, transmission, and scanning electron microscopy, or denaturated and processed for ABCG2 immunoblotting (polyclonal rabbit anti-human 1:2000, Cell Signalling). Culture supernatants were collected every 48 h for assessment of FT3 and FT4 by immuno-chemiluminescence (Beckman-Coulter). Complete decellularization and maintenance of the 3D native architecture of the lobe matrix were achieved. Thyroid-derived cells including thyrocytes, epithelialmesenchymal elements, and stem/precursors were found to migrate inside matrix septa, selfassemble like follicule, and recellularize the decellularized native follicular spaces. Thyroid hormone secretion occurred for at least 7 days. These results show that the 3D matrix of the rat thyroid may guide both differentiated and stem-like elements to self-assemble into functional follicular units, up to the lobar recellularization. This raises the possibility that a bioartificial, immuno-tolerant thyroid gland be bioengineered ex situ using autologous stem cells, and eventually transplanted.

2012 - Electro-Discharge Drilling performance on parts produced by DMLS [Articolo su rivista]
Gatto, Andrea; L., Iuliano; F., Calignano; Bassoli, Elena
abstract

Cobalt-base alloys are generally adopted in applications that require wear-, corrosion- and heat resistance. In particular, Cobalt-Chromium-Molybdenum (Co-Cr-Mo) alloy is currently being used in the aerospace and medical field. Both applications require product personalization and take advantage by parts manufacturing through additive technologies, such as Direct Metal Laser Sintering (DMLS). This technology still has limitations for the manufacture of small cavities, such as holes with diameters below 0.6mm, which require drilling of the additive manufactured part. This research aims at investigating the effects of Electro-Dicharge Drilling (EDD) on surface and subsurface features of CoCrMo samples built by DMLS. High aspect ratio holes are produced with diameter of 0.6 mm and depth fifteen times higher. Due to the absence of physical contact between tool and workpiece in EDD, machining forces are negligible and micro features can be produced with a high accuracy irrespective of the material hardness and strength. In this study, peak current, pulse-on-time and duty ratio are adopted as control factors using the Taguchi method. Material Removal Rate (MRR), Electrode Wear (EW) and surface roughness are measured as responses. Signal to noise ratios and ANOVA analysis lead to identify the significant process parameters, the levels that optimize each response and regression models for the performance criteria. From an overall evaluation of the responses an optimum process set-up can be determined which ensures high productivity and smooth surface finish, even if tool wear is medium-high. All the analysis is supported by the study of material removal mechanisms and surface morphology in the microscale, to account for the macroscopic trends.

2012 - Endocrine bioengineering: reconstruction of a bioartificial thyroid lobe using its three-dimensional (3D) stromal/vascular matrix as a scaffold. [Abstract in Atti di Convegno]
Strusi, V.; Zini, N.; Dallatana, D.; Mastrogiacomo, S.; Parrilli, A.; Giardino, R.; Lippi, G.; Spaletta, G.; Bassoli, Elena; Gatto, Andrea; Iafisco, M.; Sandri, M.; Tampieri, A.; Toni, R.
abstract

To test the feasibility of reconstructing ex situ an entire bioartificial thyroid gland suitable for transplantation we have bioengineered a rat thyroid lobe using its decellularized stromal / vascular matrix, eventually 3D recellularized with thyroid stem / precursor cells. Sprague-Dawley male rats (220–240 g) were used as thyroid donors, and lobe matrixes obtained by freezing / detergent / enzyme processing. Test matrixes were made electrondense and analyzed by microtomography (microTC). Primary thyroid cells and ABCG2-positive, thyroid stem/precursor elements were expanded and isolated either in primary monolayer or 3D matrigel cultures for 72 h, using low-glucose DMEM and high vs low serum media. Following trypsinization, 250–450.000 cells were harvested to coat the empty follicular and vascular cavities of the inner matrix surface, and grown up to 21 days in static conditions. The colonized matrixes were either fixed in aldheydes for processing by light (LM), transmission (TEM) and scanning electron (SEM) microscopy or denaturated to get total proteins, and run for ABCG2 westen blotting. Culture supernatants were collected every 48 h, and free thyroid hormone levels assessed with chemiluminescent immunoassays. Complete decellularization and maintenance of the 3D native architecture of the thyroid SVS were achieved. Thyroid-derived cell, including differentiated thyrocytes, elements showing epithelial-mesenchymal transitions, and stem/precursor cells were found both to heterotopically migrate inside matrix septa and to orthotopically aggregate, link and give rise to intracytoplasmic cavities, up to recellularize the decellularized follicular spaces. Thyroid hormone secretion occurred for at least 7 days. These results show that the natural 3D matrix of the rat thyroid acts as a scaffold to bioengineer ex situ a functional thyroid lobe with progenitor-like elements (Fig.), suggesting that a biocompatible construct can be realized for eventual transplantation replacement. Grants FIL09, PRIN082008ZCCJX4, FIRB2010RBAP10MLK7

2012 - Joining mechanisms and mechanical properties of PA composites obtained by Selective Laser Sintering [Articolo su rivista]
Bassoli, Elena; Gatto, Andrea; L., Iuliano
abstract

PURPOSEAdditive Manufacturing is today a viable industrial solution besides traditional processes. Techniques like Selective Laser Sintering address the issues of digital production and mass customization in a variety of materials. Composite parts can be obtained with specific functional and mechanical properties. Building orientation during Additive Manufacturing often causes anisotropy of parts’ properties that is still unspecified in technical information. The paper investigates the mechanical performances and failure mechanisms of an Aluminium-filled polyamide and of a new Alumina-polyamide composite produced by SLS, in comparison with unfilled PA.DESIGN/METHODOLOGY/APPROACHA specific focus is set on the evaluation of primary and secondary anisotropy in the case of metal or ceramic filler, as well as on the specific contribution of powder distribution modes and joining phenomena. Macroscopic mechanical tests and the observation of joining and failure micro-mechanisms are integrated.FINDINGSThe results prove the absence of relevant anisotropy amongst specimens that are produced with the axis parallel to the plane of powder deposition. Samples whose axis is parallel to the growth direction Z, instead, reveal a significantly different response with respect to other orientations.ORIGINALITY/VALUEAn original explanatory model is assumed and validated, based on an anisotropic distribution of the reinforcing particles during parts’ production, which determines the efficacy of the strengthening mechanisms during crack propagation.

2011 - Characterization of selective laser sintered implant alloys: Ti6Al4V And Co-Cr-Mo [Relazione in Atti di Convegno]
Gatto, A.; Bortolini, S.; Iuliano, L.
abstract

Titanium and Cr-Co-Mo alloys are the most attractive metallic biomaterials for orthopedic and dental implants: selective laser sintering technique may use these materials but it still remains limited in terms of foreseeable performances as function of process parameters. The method essentially relies on empirical, experimental knowledge and still lacks a strong theoretical basis. This paper investigates the orientation influence on mechanical performances of Ti6Al4V grade 5 and Cr-Co-Mo specimen built by selective laser sintering. The tensile strength and the rupture surface observation allow to explain the tensile strength values obtained as a function of the fine microstructure that is confirmed by metallographic observation. © Springer-Verlag Berlin Heidelberg 2011.

2011 - Dimensional tolerances and assembly accuracy of dental implants and machined- versus cast-on abutments [Articolo su rivista]
Malaguti, Giuliano; Denti, Lucia; Bassoli, Elena; I., Franchi; Bortolini, Sergio; Gatto, Andrea
abstract

Background. The clinical application of prosthetic components obtained by different manufacturing processes lacks technological foundation: the dimensional tolerance of individual parts and their assembly accuracy are not known. The rotational misfit of the hexagonal connection is critical in single tooth implant restorations, but no standard control procedures are available for its evaluation.Purpose. The research aimed at proposing a new protocol for the dimensional assessment of implant-abutment connections, based on non-contact measurement and statistical data processing. The procedure was applied to machined- and cast-on abutments, as well of the matching implants.Materials and Methods. Three groups of 5 abutments each were studied: machined titanium abutments, premachined calcinable abutments before casting procedures and the same specimens after casting. A group of 5 corresponding implants was considered as well. Twice the apothem was measured on each hexagon through an optical measuring microscope. The data were processed to obtain the international tolerance (IT) grade. The rotational misfit was then calculated using the apothems of the external and the internal hexagon.Results. All the components were classified between IT8 and IT9 and the maximum rotational misfit was around 3-4° for all the assemblies, inferior to the critical limits for the screw joint stability.Conclusion. An original measuring protocol was developed, independent of parts assembly and based on international tolerances. An objective dimensional characterization of prosthetic components and assemblies has been achieved, which is the basis for their reliability in clinical applications.

2011 - Ex situ bioengineering of bioartificial endocrine glands: A new frontier in regenerative medicine of soft tissue organs [Articolo su rivista]
R., Toni; A., Tampieri; N., Zini; V., Strusi; M., Sandri; D., Dallatana; G., Spaletta; Bassoli, Elena; Gatto, Andrea; A., Ferrari; I., Martin
abstract

Ex situ bioengineering is one of the most promising perspectives in the field of regenerative medicineallowing for organ reconstruction outside the living body; i.e. on the laboratory bench. A number of hollowviscera of the cardiovascular, respiratory, genitourinary, and digestive systems have been successfullybioengineered ex situ, exploiting biocompatible scaffolds with a 3D morphology that recapitulates thatof the native organ (organomorphic scaffold). In contrast, bioengineering of entire soft tissue organsand, in particular endocrine glands still remains a substantial challenge. Primary reasons are that noorganomorphic scaffolding for endocrine viscera have as yet been entirely assembled using biocompatiblematerials, nor is there a bioreactor performance capable of supporting growth within the thicknessrange of the regenerating cell mass which has proven to be reliable enough to ensure formation of a completemacroscopic gland ex situ. Current technical options for reconstruction of endocrine viscera includeeither biocompatible 3D reticular scaffolds lacking any organomorphic geometry, or allogenic/xenogenicacellular 3D matrices derived from a gland similar to that to be bioengineered, eventually recellularizedby autologous/heterologous cells. In 2007, our group designed, using biocompatible material, anorganomorphic scaffold–bioreactor unit for bioengineering ex situ the human thyroid gland, chosen as amodel for its simple anatomical organization (repetitive follicular cavities). This unit reproduces both the3D native geometry of the human thyroid stromal/vascular scaffold, and the natural thyrocyte/vascularinterface. It is now under intense investigation as an experimental tool to test cellular 3D auto-assemblyof thyroid tissue and its related vascular system up to the ex situ generation of a 3D macroscopic thyroidgland. We believe that these studies will lay the groundwork for a new concept in regenerative medicineof soft tissue and endocrine organs; i.e. that the organomorphism of a biocompatible scaffold–bioreactorcomplex is essential to both the 3D organization of seeded stem cells/precursor cells and their phenotypicfate as glandular/parenchymal/vascular elements, eventually leading to a physiologically competent andimmuno-tolerant bioconstruct, macroscopically suitable for transplantation and clinical applications.

2011 - New approaches to prototype 3D vascular-like structures by additive layer manufacturing. [Relazione in Atti di Convegno]
Bassoli, Elena; Denti, Lucia; Gatto, Andrea; A., Paderno; G., Spaletta; N., Zini; V., Strusi; D., Dallatana; R., Toni
abstract

In this paper preliminary results are summarized on the use of a combined Additive Layer Manufacturing (ALM) and indirect replication methodology to reconstruct reticular-like, three-dimensional (3D) structures mimicking the 3D vascular network of the adult human thyroid gland. In a first step, we developed a fractal-like algorithm capable of modeling the native arterial distribution of the adult thyroid lobe, allowing for vascular growth within its geometrical domain. Although some arbitrary simplifications were adopted, yet the vascular density of the computational simulation showed good consistency with that of a native thyroid lobe. In a second step, single vascular branches were prototyped based on the STL output of the algorithm and ALM techniques, up to the achievement of a model having satisfactory geometrical/morphological accuracy. In a third step, the problem of reproducing the vascular geometry with a biocompatible polymer was ad-dressed, and different protocols of replication technology were evaluated. Limits and possible methodological solutions are discussed.

2011 - Performance Optimization in Machining of Aluminium Alloys for Moulds Production: HSM and EDM [Capitolo/Saggio]
Gatto, Andrea; Bassoli, Elena; L., Iuliano
abstract

Aluminium alloys offer many machining advantages such as excellent machinability and finish degree with high cutting speed, low cutting forces, outstanding tool life. Elevated thermal exchange and weight reduction compared to steels are additional characteristics that lead to increasing applications in the automotive and aerospace industry and in the field of mould production. Relatively recent Aluminium alloys derived by aeronautical uses offer very high strength and hardness: the gap with steels is thus reduced or even reversed in terms of specific properties. Two examples are Al 2219 and Al 7050. If the first examples of Aluminium moulds for plastic injection were limited to preproduction, the properties of these new alloys match the requirements of medium production volumes, which are also the main market demand.The research focuses on two distinct operations typical of the tooling phase: High Speed Milling (HSM) and Electro Discharge Machining (EDM). In both cases the machining performance is evaluated in specific tests through a multiscale approach: measurements of the macroscopic process outputs are merged with the investigation of mechanisms at a microscopic level. The methodology enhances optimization chances with respect to traditional practice.As to milling operation, several studies prove that Aluminium alloys allow the advantageous adoption of high cutting speed, ensuring time and cost savings together with excellent surface finish and low tool wear. Yet, the traditional laws between cutting parameters do not apply to the field of high-speed machining and the mechanisms of chip removal still need investigation. In order to appraise the machinability of Al 2219 and Al 7050 alloys, high speed milling tests using uncoated carbide tools are performed. The tests are carried out on Al 7075 as well, an alloy of common employment for preproduction moulds, to provide control data. Cutting speed ranges from 600 to 2200 m/min and feed per tooth between 0.075 and 0.18 mm/tooth. Correlations between cutting parameters and surface finish, tool wear and chip formation mechanisms are studied with the aid of SEM observation and EDX semi-quantitative analysis. The best surface finish is obtained for Al 7050 with high cutting speed and low feed. No tool wear is observed in the considered conditions. Microscope observation of tools and chip proves that surface finish is ruled by tool-chip adhesion and that alloys having almost the same chemical composition can provide substantially different results due to grain dimension and distribution.EDM is used for the machining of complex shapes and textures typical of plastic injection moulds. Aim of this research is to verify the EDMachinability of the Aluminum alloys previously studied with regard to HSM. Literature studies on the specific subject are very rare. EDM tests are planned and performed using electrolytic copper electrodes on Al 7050 and Al 2219, plus Al 7075 as a control. A benchmark is chosen whose geometry points out the typical problems of moulds machining and allows an easy and significant dimensional characterization, because of the presence of different geometrical features and relative orientations. Roughing, semifinishing and finishing cycles are conducted; then the effect of process parameters on dimensional tolerance, surface finish and electrode wear is studied. Moreover, the electrodes and the machined surfaces are observed through optical- and scanning electron microscope (OM, SEM) to verify the presence and composition of deposits on the electrodes surfaces, as well as the eroded surfaces morphology on the workpieces. No remarkable differences can be identified as to dimensional tolerances between the three alloys. A slight trend to give lower roughness values can be noticed for the alloy 7050. The results are coherent with the regular morphology observed on the machined surfaces of this alloy. The observation of the erosion mechanisms allows to affirm that, for th

2011 - Thermoplastic Resin Transfer Moulding in a rapid manufactured mould [Relazione in Atti di Convegno]
E., Atzeni; F., Calignano; L., Iuliano; P., Minetola; A., Salmi; Bassoli, Elena; Denti, Lucia; Gatto, Andrea
abstract

Resin Transfer Moulding (RTM) is a low-cost process for the production of composite parts with thermosetting resins. However, the economic convenience is lost in the case of large components, such as aeronautical panels, because of the high tooling cost. Step milling of a resin master for the electro-deposition of a nickel shell is proposed in this study as a valid alternative for the fabrication of a resin transfer mould. This solution allows overcoming the limitations regarding part size and cutting down tooling costs, but the expected dimensional accuracy needs to be assessed. On the field of materials, innovative thermoplastic resins are now available that can be used in the formof lowviscosity oligomers for optimal mould filling and fibre impregnation. Subsequent in situ polymerization provides high toughness composites. Cyclic Butylen Terephtalate (CBT), which polymerizes into PBT (Poly-Butylen Terephtalate), is studied in this work. The research focuses on two objectives: quantifying the dimensional accuracy of the technological chain and setting up the process of in situ polymerization.

2010 - Artificial teeth manufacturing: Inspection of mould and teeth by contactless scanning systems [Relazione in Atti di Convegno]
Atzeni, E.; Iuliano, L.; Minetola, P.; Salmi, A.; Gatto, A.
abstract

The recent development of non-contact digitizing systems dedicated to dental applications has introduced innovative procedures, based on Reverse Engineering techniques, for the production of artificial teeth. Starting from the reconstructed 3D model of each tooth, first the mould CAD model is created and then the milling path is computed for machining. At the moment there is no indication of the quality of such innovative procedure, so it is investigated in this study by evaluating the deviation introduced by each manufacturing step. A machined mould for the production of acrylic molars and premolars is inspected by means of a contactless scanner and some teeth are selected as manufactured samples. Scan data of such samples allow to evaluate the deviations introduced by each operation. A comparison of two optical digitizers is based on the results of this study and economic considerations related to costs and times are also included. © 2010 Taylor & Francis Group.

2010 - Characterization of Selective Laser Sintered Implant Alloys: Ti6Al4V abd Co-Cr-Mo [Relazione in Atti di Convegno]
Gatto, Andrea; Bortolini, Sergio; L., Iuliano
abstract

Titanium and Cr-Co-Mo alloys are the most attractive metallic biomaterials for orthopedic and dental implants: selective laser sintering technique may use these materials but it still remains limited in terms of foreseeable performances as function of process parameters. The method essentially relies on empirical, experimental knowledge and still lacks a strong theoretical basis. This paper investigates the orientation influence on mechanical performances of Ti6Al4V grade 5 and Cr-Co-Mo specimen built by selective laser sintering. The tensile strength and the rupture surface observation allow to explain the tensile strength values obtained as a function of the fine microstructure that is confirmed by metallographic observation.

2010 - DMLS DENTAL ALLOYS VS TRADITIONAL TECHNIQUE [Abstract in Rivista]
Bortolini, Sergio; Gatto, Andrea; Natali, Alfredo; Y., Ucar; G., Montin; Bassoli, Elena; Denti, Lucia; Consolo, Ugo; L., Iuliano; T., Akova
abstract

Additive Layer Manufacture (ALM) of dental prostheses allows the direct fabrication of parts from CAD data, replacing a human-sensible process with a faster reliable automatic one. Direct Metal Laser Sintering (DMLS) of Cr-Co alloys produces parts to be directly finished with ceramic and employed. PURPOSE: This study evaluated (1) the application of DMLS process for obtaining final dental prostheses in Co-Cr alloy, to compare mechanical characteristics of cast parts and layer-manufactured ones produced with different alloys and processes; and (2) the effect of porcelain firing cycles on mechanical properties. METHODS: This study was conducted on three classes of tensile specimens in five groups of six specimens: class 1 – 12 specimens built by DMLS (PM100T – Phenix System, France) with Co-Cr powder NOBIL 4000S (NOBIL METAL - Italy) divided in two groups (6 specimens were processed with ceramic heat treatment); class 2 – 12 specimens built by traditional lost-wax casting from Co-Cr bars for fixed prostheses V-CERAM MAGI LINE (SHERA - Germany) divided in two groups (6 specimens were processed with ceramic heat treatment); class 3 – 6 tensile specimens built by traditional lost-wax casting from Cr-Co bars for partial removable prostheses REMANIUM 800+ (Dentaurum - Germany). RESULTS: UTS of all sintered specimens (1174±165 MPa) was higher than of cast ones (503±45 MPa, 499±62 MPa, 712±51 MPa, respectively, for as cast Co-Cr, heat treated Co-Cr, and Remanium) where many porosities were found. UTS decreases after heat-treatment both for cats and DMLS parts. Yield strength was also highest for the laser sintered group (1148±161 MPa).No significant idfference was found for the elastic modulus of compared groups (P=0.398). CONCLUSIONS: DMLS of Co-Cr alloys produces excellent strength and absence of defects compared to traditional casting. This result is due to the fine microstructure obtained by DMLS (high thermal rate, heterogeneous nucleation).

2010 - Evaluation of innovative techniques for dental crowns manufacturing [Relazione in Atti di Convegno]
Salmi, A.; Atzeni, E.; Gatto, Andrea; Iuliano, Luca; Minetola, P.
abstract

Recently, Reverse Engineering (RE) and Additive Manufacturing (AM) have proven to be interesting techniques alternative to traditional procedures in dental applications, such as crown manufacturing. The geometry of a stone replica can be digitized by a three-dimensional scanner. From the points clouds a Virtual Model (VM) is generated and tooth caps could be designed on it and manufactured by Computer Aided Manufacturing (CAM) or employing AM techniques. The sequence from replica digitization (VM) to cap fabrication involves many production steps, each one inevitably inducing dimensional errors. However, the information given by systems suppliers or present in literature is lacking and does not allow comparison among different manufacturing systems. Therefore, it becomes important to investigate new technologies to quantify their accuracy and precision. Currently, there is not a standard methodology for evaluating the error introduced by each step of the manufacturing cycle, from the scanning of the replica to the final dental device. Moreover, to have comparable data, a suitable benchmark must be defined (Atzeni et al., 2009). In literature a few benchmarks based on standard geometries were proposed for dental applications (Brosky et al., 2002; DeLong et al., 2003), but they appear lacking because differences from posterior and anterior teeth shapes, tooth position along the dental arch, and three dimensional arrangement of teeth are disregarded.

2010 - FRACTURE RESISTANCE ANALYSIS OF SINTERED AND CASTED COBAL/CROMIUM ALLOYS [Abstract in Rivista]
Natali, Alfredo; Bortolini, Sergio; G., Montin; Gatto, Andrea; L., Iuliano; Bassoli, Elena; Denti, Lucia; Y., Ucar; A., Tolga; Consolo, Ugo
abstract

THIS STUDY WANTS TO EVALUATE THE APPLICATION OF SLS PROCESS FOR OBTAINING FINAL DENTAL PROSTHESIS IN CR-CO ALLOY, DEVELOPING EXPERIMENTAL PLAN WITH THE PURPOSE TO MADE A COMPARATIVE ANALYSIS OF MECHANICAL CHARACTERISTICS BETWEEN CASTS PARTS AND SINTERED ONES PRODUCTED WITH DIFFERENT ALLOYS AND PROCESSES.

2010 - Mechanical characterisation of PA-Al2O3 composites obtained by SLS [Articolo su rivista]
G., Berti; L., D’Angelo; Gatto, Andrea; L., Iuliano
abstract

The increasing need for strongly personalized products, to be produced in few parts with short time-to-market, makes Rapid Tooling and Manufacturing competitive with respect to traditional processes.The great advantages, in terms of reduced times and costs for the product’s launching, can be properly exploited only through a deep knowledge concerning the parts’ performances as a function of the process parameters. A promising material for application in SLS technology is polyamide composite (PA-Al2O3). An experimental campaign was started and some specimens, with different orientations in regard to powder deposition plane and laser path, have been manufactured and tested. Mechanical properties have been determined using tensile test performed both at room temperature and at 100 °C.The sintered material shows an evident main anisotropy between the growth direction (z axis) and the plane XY, as well as in this plane the parts seem to be not sensitive to the sintering direction at room temperature (x, y, xy). At 100°C the effect of sintering direction on XY plane becomes more evident and a different behaviour results considering x and y direction respectively (secondary anisotropy). Scanning Electron Microscopy (SEM), Atomic Force and Lateral Force Microscopy (AFM and LFM) have been carried out to understand the effect of the manufacturing anisotropy on the mechanical performances, both in terms of additive construction and laser sintering strategy. The observation of the rupture surfaces showed that at room temperature cracks originate from the external surface and propagate initially by the ductile failure of the polymeric matrix, up to the sudden fracture of the whole section

2010 - Microwave rapid debinding and sintering of MIM/CIM parts [Relazione in Atti di Convegno]
Veronesi, Paolo; Leonelli, Cristina; Poli, Giorgio; Denti, Lucia; Gatto, Andrea
abstract

Microwave assisted thermal debinding of parts obtained by Metal Injection Moulding (MIM) or Ceramic Injection Moulding (CIM) could benefit from the heating selectivity, having the organic binder to preferentially absorb microwaves, thus accelerating the conventional process, which has to rely on heating by conduction. This is particularly useful when dealing with ceramic powders having low thermal conductivity, but also more conductive materials can be treated faster if the maximum temperature difference inside each part is kept low.Once the organic binder is removed, microwaves at 2.45 GHz can be used to rapidly sinter the obtained brown parts, minimizing grain growth.In this work, microwave assisted debinding and sintering of MIM/CIM parts, made of stainless steel, alumina and titania is studied, using numerical simulation to investigate the presence of localised effects ascribable to the electromagnetic field distribution in the powder compacts.

2010 - On the effects of build orientation in powder-fed Additive Layer Manufacture of steel 316L [Relazione in Atti di Convegno]
Bassoli, E.; Gatto, A.; Sewell, N. T.; Johns, D.
abstract

The major interest in the field of Additive Layer Manufacturing is at present the emancipation from prototyping towards industrial production. To this aim, a significant limitation is still the difficulty in predicting part characteristics and ensure robustness and repeatability. Laser Consolidation (LC) is a powder-fed process producing net-shape metal components with good metallurgical soundness, high strength and duc-tility. The specific LC head configuration is likely to cause direction dependant features varying not only along and perpendicular to the build direction, but also within each layer. Aim of the research is to investigate the mechanical properties and microstructure of AISI 316L parts built by LC, with a specific focus on the ef-fects of the direction of build, either axially aligned with the head or orthogonal to it. The results confirmed high hardness and strength and excellent ductility of LC parts. Anisotropy of mechanical response was quanti-fied and related to microstructure.

2010 - Surface and subsurface features of micro electro drilled part produced by sls [Relazione in Atti di Convegno]
Gatto, Andrea; Iuliano, Luca; Calignano, F.
abstract

Additive manufacturing processes are time-compression-technologies that create near-net shaped components from CAD models to product deposition. The main focus of this technology is to produce parts, as near as possible close to their final shape and contour, implementing non-chipping techniques. In this way the manufacturing gives the possibility of a finished product with minimal cutting. Near-net shape technology also generates the opportunity to reduce the productive steps for a given process chain. Both the abovementioned characteristics have the same main goal: achieving cost reduction. This fundamental target incorporates several other advantages, such as: reduction of process variability, quality improvement in the finished product and the possibility to focus the design of mechanical devices on functional features, eliminating technical constraints imposed by the process. Electrical discharge machining (EDM) is one of the most extensively used non-conventional material removal processes. In addition, EDM does not make direct contact between the electrode and the workpiece eliminating mechanical stresses, chatter and vibration problems during machining. Recent progress made in the field of aviation, space, automobile, electronics and computer, medical, optics, miniature manufacturing and others (Kumar, 2008; Emmelmann C. et al., 2009; Vandenbroucke B. et al., 2007) has created the need for small and micro-size holes with high aspect ratio in extremely hard and brittle materials. The increasing use of these alloys led to analyze, in this research, the effects of micro electro-discharge drilling on surface e subsurface features of Cr-Co-Mo specimen built by selective laser sintering. The ability to create near-net shape componenst in CrCo with additive manufacturing and the micro-drilling of the components are very recent. For this reason, are not present critical overview on the subject in the literature.

2009 - A benchmark for accuracy evaluation of dental crowns up-to-date manufacturing [Relazione in Atti di Convegno]
E., Atzeni; L., Iuliano; Salmi, P. M. i. n. e. t. o. l. a. A.; Gatto, Andrea
abstract

In recent years, digitizing and automation have gained an important role in manufacturing of dental devices. Instead of the traditional plaster model procedure, scanning techniques may be used for the geometry acquisition. Point clouds are processed and converted into standard CAD models, from which metal tooth cap can be fabricated by milling, integrating CAM tool, or by rapid manufacturing (RM) techniques. Good quality control is critical to ensure the crown fit: an improper fit could cause crown falling off. So far there is no standard procedure for evaluating quality of both 3D digitization and milling/RM cap making processes. Thus, a specific benchmark is designed to represent critical features of a stone replica, like a dental arch with studs resembling teeth prepared for crowns installation. The benchmark is then produced and meas-ured by means of a coordinate measuring machine.

2009 - Artificial teeth manufacturing: inspection of mould and teeth by contactless scanning system [Relazione in Atti di Convegno]
E., Atzeni; L., Iuliano; Salmi, P. M. i. n. e. t. o. l. a. A.; Gatto, Andrea
abstract

The recent development of non-contact digitizing systems dedicated to dental applications has introduced innovative procedures, based on Reverse Engineering techniques, for the production of artificial teeth. Starting from the reconstructed 3D model of each tooth, first the mould CAD model is created and then the milling path is computed for machining. At the moment there is no indication of the quality of such inno-vative procedure, so it is investigated in this study by evaluating the deviation introduced by each manufactur-ing step. A machined mould for the production of acrylic molars and premolars is inspected by means of a contactless scanner and some teeth are selected as manufactured samples. Scan data of such samples allow to evaluate the deviations introduced by each operation. A comparison of two optical digitizers is based on the results of this study and economic considerations related to costs and times are also included.

2009 - Densification and coarsening of laser sintered green parts by microwave technique [Relazione in Atti di Convegno]
Veronesi, Paolo; Gatto, Andrea; L., Iuliano
abstract

Microwave sintering of SLS green parts made of 420L stainless steel has been performed applying microwaves at the frequency of 2.45 GHz. The use of single mode and multi-mode microwave furnaces allowed to find the most suitable sintering conditions in absence of auxiliary microwave absorbers. In case the electric field intensity reaches a threshold value, able to trigger breakdown phenomena, sintering is rapidly achieved, but at the cost of homogeneity and process controllability. A lower electric field intensity allows, instead, to achieve complete sintering of the green parts in 10 to 20 minutes time, which results considerably shorter than current state of the art conventional sintering of SLS green parts. Comparison between mi-crowave and conventionally sintered parts showed that the final product present a similar microstructure, with the presence of Cr-rich regions whose extension is a function of the microwave processing time

2009 - Development of a low cost eye gaze tracker [Relazione in Atti di Convegno]
Bulf, Luca; Fonda, Sergio; Marchiandi, G.; Gatto, Andrea
abstract

Eye gaze tracker is a device for monitoring and recording eye motion and related eye data. It is a hands-off, not intrusive, remote human-computer interface that can be used to track a user's gazepoint. It allows an operator to interact with their environment using only their eyes. During 2 decades of development, hundreds of eyegaze, eye-controlled, computer/communication systems have been sold around the world, primarily as an assistive device for people with disabilities and as a tool for human factors research. Gaze information plays an important role in identifying a person's focus of attention. The information can provide useful communication cues to a multimodal interface. A person's gaze direction is determined by two factors: the orientation of the head, and the orientation of the eyes. While the orientation of the head determines the overall direction of the gaze, the orientation of the eyes determines the exact gaze direction and is limited by the head orientation. To be applied in general computer interfaces, an ideal eye tracker should: be precise to minutes of arc; have repetitive behaviour; work under different conditions such as lighting fluctuations, operator with glasses and contact etc; allow for free head motion; be easy to use on a variety of subjects. This paper regards the development of an economic and ergonomic eye gaze tracker using time compression techniques. A low cost and custom fit approach is used in the development of this Eye gaze tracker: a single low-cost B/W mini-camera (Table 1) is used to acquire video images. A good image contrast is obtained using one IR LED, positioned in proximity of the camera, with orientation suitable to produce the dark-pupil effect: this setup allows an easy pupil image identification. The device shape is designed on a head virtual model obtained from the digitalization of a physical pattern; the point cloud of the head physical model is acquired using a laser scanner. The functional prototypes are produced using the fused deposition modelling (ABS) and selective laser sintering techniques(aluminium/polyammide). Fifty users (students) tested the functional prototypes, complete of all components to evaluate the functional and ergonomic device characteristics. The final cost of the prototype obtained is about 10% of the cost of the product available in the market.

2009 - Mechanical and SEM Characterisation of ABS Components obtained by Fused Deposition Modelling [Relazione in Atti di Convegno]
Berti, G.; D’Angelo, L.; Gatto, Andrea; Iuliano, L.
abstract

New ABS for Fused Deposition Modelling (FDM) has been recently presented, characterized by high mechanical performances, finishing quality and high temperature strength. Both functional prototypes and rapid manufactured parts can thus be produced directly from the CAD representation. The great advantages, in terms of reduced times and costs for the product’s launching, can be properly exploited only through a deep knowledge concerning the parts’ performances as a function of the construction process. The present research is aimed at overcoming the trial-&-error approach diffused in industrial practice and filling a gap in existing literature. To this aim, specimens with different orientations in regard to filament deposition plane, have been manufactured and tested. Tensile tests, both at room temperature and at 70°C, have been used to determine the mechanical properties. As the extruded material has a tissutal structure, its anisotropic behaviour has been confirmed by experiments. The mechanical properties seem insensitive to the deposition direction (x, y, xy), while they worsen in the growth direction (z axis). This mechanical behaviour has been observed at both temperatures. An accurate SEM characterization has been carried out (1) to understand the effect of the manufacturing anisotropy on the mechanical performances, and (2) to comprehend how failure occurs and the way it is influenced by test temperature. Starting from the experimental results, an analytical material model has been developed, able to take into account the void percentage and, therefore, suitable to predict the mechanical behaviour of ABS components produced by means of the FDM technique.

2009 - Microwave Rapid Sintering of Nanostructured Stainless Steel Metal Powders [Relazione in Atti di Convegno]
Veronesi, Paolo; Leonelli, Cristina; Poli, Giorgio; Bassoli, Elena; Denti, Lucia; Gatto, Andrea
abstract

Nanostructured AISI430 stainless steel powders, obtained by high energy milling have been uniaxially pressed in order to obtain 8 mm diameter cylindrical compacts. Microwave sintering of the green compacts has been performed in a single mode microwave applicator, at 2.45 GHz. Maximum sintering temperature of each sample, monitored using a sapphire optical fibre, was varied in the 1000-1200°C range, with heating rates in the 20-30 K/s range, applying 1200 W of microwave forward power. Dense nanostructured samples, with less than 1% porosity were obtained, presenting small local variation of Cr content in proximity of the necking region. Rapid microwave sintering helps maintaining the nanostructure, despite a non homogenous densification due to the uneven electromagnetic field distribution in the single-mode applicator

2009 - “Microwave Rapid Sintering of Nanostructured Stainless Steel Metal Powders”,, Vol. 3, , Denmark, 2009, 143-148, ISBN [Relazione in Atti di Convegno]
Veronesi, Paolo; Leonelli, Cristina; Poli, Giorgio; Bassoli, Elena; Denti, Lucia; Gatto, Andrea
abstract

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2008 - A study on the relationship between intraglandular arterial distribution and thyroid lobe shape: implications for biotechnology of a bioartificial thyroid [Articolo su rivista]
R., Toni; C., DELLA CASA; M., Bodria; G., Spalletta; R., Vella; S., Castorina; Gatto, Andrea; G., Teti; M., Falconi; T., Rago; P., Vitti; F., Sgallari
abstract

We have recently hypothesized that structural and secretory components of the adult human thyroid gland maintain constant reciprocal and geometrical relationships, even if changes occur in the three-dimensional (3D) architecture of any of these elements. This means that thyroid morphology could be studied from the point of view of a 3D topology. As a consequence, we have investigated anatomical aspects that could support this assumption. In the present study, we show that the presence of a constant relationship can be demonstrated between the vascular arrangement of the gland, including the extension of intraglandular arterial fields, arterial anastomoses and arterial calibers, and the shape as well as volume of the thyroid. Specifically, a statistically significant difference has been found between the network amplitudes of the superior and inferior thyroid arteries in relation to either a conic or an ellipsoidal geometry of the thyroid lobe. In addition, a direct relationship has been implicated between the distribution of arterial anastomoses and the behavior of the lobe as a single hemodynamic unit. Finally, a statistically significant correlation has been observed between average arterial caliber of the inferior thyroid artery and thyroid volume. On the basis of these results, we propose a model of architectural assembly between stromal and parenchymal elements of the adult thyroid that might prove useful in designing a bioartificial gland ex situ. Potential clinical applications of this principle in regenerative medicine of other endocrine organs are highlighted.

2008 - Additive Layer Manufacture of Tensile Tests Specimens in Stainless Steel 316L by Laser Consolidation [Relazione in Atti di Convegno]
N. T., Sewell; Bassoli, Elena; Gatto, Andrea; K. E., Evans
abstract

Laser Consolidation (LC) is an Additive Layer Manufacturing (ALM) process which produces net-shape fully dense metal parts. LC uses a synchronised pulsed Nd:YAG laser and a powder delivery unit to build parts which exhibit excellent mechanical properties and impact resistance. These properties may be tailored at build time by modifying build parameters but the non-coaxial nature of the LC head assembly causes direction dependant features. This paper investigates the mechanical properties and microstructure of AISI 316l parts built by LC. Tensile test specimens were constructed in different orientations and underwent tensile testing and SEM observation. All the specimens exhibited high elongation at break and Ultimate Tensile Strength (UTS) but parts properties were significantly affected by build direction. Parts built by relative head movement along the plane of LC head assembly (X direction) were more ductile and stronger compared with parts constructed orthogonally. SEM analysis revealed a higher presence of voids in the latter. It was speculated that the voids were the major factor in the reduction in strength and ductility of the parts.

2008 - Additive Layer manufacture of Tensile test specimens in stainless steel 316l by Laser Consolidation [Articolo su rivista]
Sewell, N. T.; Bassoli, E.; Gatto, A.; Evans, K.
abstract

Laser Consolidation (LC) is an Additive Layer Manufacturing (ALM) process which produces net-shape fully dense metal parts. LC uses a synchronised pulsed Nd:YAG laser and a powder delivery unit to build parts which exhibit excellent mechanical properties and impact resistance. These properties may be tailored at build time by modifying build parameters but the non-coaxial nature of the LC head assembly causes direction dependant features. This paper investigates the mechanical properties and microstructure of AISI 316l parts built by LC. Tensile test specimens were constructed in different orientations and underwent tensile testing and SEM observation. All the specimens exhibited high elongation at break and Ultimate Tensile Strength (UTS) but parts properties were significantly affected by build direction. Parts built by relative head movement along the plane of LC head assembly (X direction) were more ductile and stronger compared with parts constructed orthogonally. SEM analysis revealed a higher presence of voids in the latter. It was speculated that the voids were the major factor in the reduction in strength and ductility of the parts.

2008 - Microwave assisted debinding and sintering of nanostructured metal powders: modeling and experimental results [Abstract in Atti di Convegno]
Leonelli, Cristina; Veronesi, Paolo; Denti, Lucia; Gatto, Andrea
abstract

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2008 - Microwave assisted sintering of green metal parts [Articolo su rivista]
Leonelli, Cristina; Veronesi, Paolo; Denti, Lucia; Gatto, Andrea; L., Iuliano
abstract

Microwave processing has gained worldwide acceptance as a novel method for heating and sintering a variety of materials, as it offers specific advantages in terms of speed, energy efficiency, process simplicity, finer microstructures, and lower environmental hazards.Microwave assisted post-treatment of green metal parts (AISI 420 metal powder with 2–3 wt% polymeric binder) proved to be a new method, suitable for near-net-shape and net-shape manufacturing.Green parts exposed to high intensity microwave fields, using either single mode or multimode microwave applicators operating at 2.45 GHz ISM frequency, were investigated in terms of densification behaviour, microstructure and joining micromechanism. The results, in terms of microstructure and shape retention are comparable to the conventional heating ones, reported in literature, but they have been obtained in much shorter time.

2008 - Study of the EDM process effects on Aluminum alloys [Articolo su rivista]
L., Iuliano; M. G., Violante; Gatto, Andrea; Bassoli, Elena
abstract

Aluminum alloys offer many machining advantages such as excellent machinability and finish degree, elevated thermal exchange, reduction of weight. Till now aluminum moulds have been employed only for preproduction; with the new alloys Al 2219 and Al 7050, which have outstanding properties, we can think about medium productions of plastic components obtained by injection molding. Electro Discharge Machining is used for the machining of complex shapes typical of plastic injection moulds. In order to evaluate the machinability of these new alloys, some EDM tests have been planned. Comparison tests have also been done on Al 7075, an alloy of common employment for preproduction moulds, to have precise control data. The tests allowed understanding the correlations among process parameters, dimensional tolerances, surface finish and electrode wear. Moreover, the electrodes and the machined surfaces have been observed at the optical- and scanning electron microscope (OM, SEM) to understand the EDM mechanisms.

2007 - 3D Printing technique applied to Rapid Casting [Articolo su rivista]
Bassoli, Elena; Gatto, Andrea; L., Iuliano; M. G., Violante
abstract

Purpose To verify the feasibility and evaluate the dimensional accuracy of two Rapid Casting solutions based on 3D Printing technology: investment casting starting from 3D-printed starch patterns and the ZCast process for the production of cavities for light-alloys castings.Design/methodology/approach Starting from the identification and design of a benchmark, technological prototypes were produced with the two Rapid Casting processes. Measurements on a CMM machine allowed calculating the dimensional tolerances of the proposed technological chains. The predictive performances of CAE software were verified when applied to the ZCast process modelling.Findings The research proved that both the investigated Rapid Casting solutions are effective in obtaining cast technological prototypes in short times and with low costs, with dimensional tolerances that are completely consistent with metal casting processes.Practical implications The research assessed the feasibility and dimensional performances of two Rapid Casting solutions, providing data that are extremely useful for the industrial application of the considered technologies. Originality/value The paper deals with experimental work on innovative techniques on which data are still lacking in literature. In particular, an original contribution to the determination of dimensional tolerances and the investigation on the predictive performances of commercial CAE software is provided.

2007 - Development of a model to optimize the sand shape and post process parameters for parts produced by Direct Croning process [Relazione in Atti di Convegno]
Gatto, Andrea; L., Iuliano; F., Cannella
abstract

The complex sand cores and moulds for prototype sand, castings produced by Selective Laser Sintering (SLS), result fragile once they are removed from the supporting uncured sand. Therefore, they require Post Curing to become dimensionally stable and capable of successfully undergoing the rigors of the metal casting process. In this paper the effects of post curing process parameters on the performances of sand parts produce by SLS are investigated. The sand characteristics and Post Curing parameters choice must take into account the presence of two antagonistic needs: the decrease of gas production during the casting decreasing the presence of volatile components of the binder, and the improvement of the mechanical performances increasing the binder weight percentage (Subramanian K. & Al, 1995, ). Three different phenolic resin coated sands were investigated: 1) silica SiO2; 2) synthetic mullite 3Al2O32SiO2 ; 3) synthetic mullite + SiO2. The compressive strength of the sand specimen was reported VS time and temperature post process parameters. Increasing curing temperature and time, the mechanical performances improve up to a maximum value than decrease. A benchmark was defined and used to evaluate the post process parameters influence on dimensional and shape tolerance. The mechanical behaviour of a part reflects the micro joining mechanisms between the particles a model is proposed to understand how the post curing parameters can influence the performances of the SLS products.This paper examines also the reliability of stress distribution obtained by FEA, comparing the results with the experimental data obtained using the mullit+SiO2 sand. Finite Element Analysis (FEA) allows to construe the stress distribution in the grains contact as a function of the post process parameters, making it possible to define the grains shape optimising the mechanical properties of the obtained structure: the sand may be designed and its use can be optimised without long times and expensive tests.

2007 - Mechanical characterisation of PAAl2O3 composites obtained by selective Laser Sintering [Relazione in Atti di Convegno]
G., Berti; L., Dangelo; Gatto, Andrea; L., Iuliano
abstract

The increasing need for strongly personalized products, to be produced in few partswith short time-to-market, makes Rapid Tooling and Manufacturing competitive withrespect to traditional processes.The great advantages, in terms of reduced times and costs for the product’slaunching, can be properly exploited only through a deep knowledge concerning theparts’ performances as a function of the construction process.A promising material for application in SLS technology is PA-Al2O3 composite. Anexperimental campaign was started and some specimens, with different orientations inregard to powder deposition plane and laser path, have been manufactured andtested. Mechanical properties have been determined using tensile test performed bothat room temperature and at 100 °C.The sintered material shows an evident anisotropy in the growth direction (z axis), aswell as it seems to be not sensitive to the sintering direction at room temperature (x, y,xy). At 100°C the effect of sintering direction becomes more evident and a differentbehaviour results considering x and y direction respectively.Accurate SEM characterization has been carried out to understand the effect of themanufacturing anisotropy on the mechanical performances, both in terms of additiveconstruction and laser sintering strategy. The observation of the rupture surfacesshowed that cracks originate from the external surface and propagate initially by theductile failure of the polymeric matrix, up to the sudden fracture of the whole section.

2007 - Pre-Sintered MIM Brown Parts Obtained by Microwave-Assisted Binder Remova [Relazione in Atti di Convegno]
Veronesi, Paolo; D., Belviso; Denti, Lucia; Gatto, Andrea; Leonelli, Cristina
abstract

Microwave assisted thermal debinding of parts obtained by Metal InjectionMoulding (MIM) was studied using Design of Experiment techniques to reducethe number of virtual experiments needed to gather information regardingbinder removal. The optimization, in terms of speed, heating homogeneityand energy efficiency of the early stages of this process in an existing2-feeds multimode applicator operating at 2.45 GHz has been reached withnumerical simulation used to perform the virtual experiments. The obtainedmodel was used to determine the optimum debinding conditions, which wereexperimentally tested in a laboratory multimode applicator. Samplecharacterization, before and after sintering, in terms of strength andfinal density, with respect to an equivalent industrial production, wasused to assess the optimized process. A process time reduction of morethan 6 times was achieved. In case of MIM parts made of 430L steel,material not prone to high temperature oxidation, the preferentialmicrowave absorption by the metallic powders resulted also in apre-sintering treatment which improves the brown parts strength and favorstheir handling during the subsequent sintering stage.

2007 - Pre-sintered mim brown parts obtained by rapid microwave-assisted binder removal [Relazione in Atti di Convegno]
Veronesi, P.; Belviso, D.; Denti, L.; Gatto, A.; Leonelli, C.
abstract

Microwave assisted thermal debinding of parts obtained by Metal Injection Moulding (MIM) was studied using Design of Experiment techniques to reduce the number of virtual experiments needed to gather information regarding binder removal. The optimization, in terms of speed, heating homogeneity and energy efficiency of the early stages of this process in an existing 2-feeds multimode applicator operating at 2.45 GHz has been reached with numerical simulation used to perform the virtual experiments. The obtained model was used to determine the optimum debinding conditions, which were experimentally tested in a laboratory multimode applicator. Sample characterization, before and after sintering, in terms of strength and final density, with respect to an equivalent industrial production, was used to assess the optimized process. A process time reduction of more than 6 times was achieved. In case of MIM parts made of 430L steel, material not prone to high temperature oxidation, the preferential microwave absorption by the metallic powders resulted also in a pre-sintering treatment which improves the brown parts strength and favors their handling during the subsequent sintering stage.

2007 - Studies of rapid microwave sintering of green parts [Relazione in Atti di Convegno]
Veronesi, Paolo; Leonelli, Cristina; Denti, Lucia; Gatto, Andrea; L., Iuliano
abstract

This paper regards the application of microwave for the sintering of green parts produced by selective laser sintering (SLS). Heating tests were performed on 420L stainless steel cylindrical (20 mm diameter; 20 mm height). The parameters of the electromagnetic field distribution during microwave sintering of the specimens were optimized for the heating treatments. The dates obtained from preliminary tests were used to carry out further heating treatments. This paper shows the possibility of achieving rapid consolidation in single mode and multimode applicators operating at 2.45 GHz, in less than 20 minutes. This phenomenon is confirmed by a micro-scale numerical modelling of the distribution of the electromagnetic field around the metal particles that evidence a favourable necking stage promoted by local electric field concentration among the spherical particles. The consolidated parts, however, depending on the microwave heating conditions, can present sensitisation due to the formation of chromium carbides, favoured by the C abundance provided by the decomposing organic binder.

2006 - Complementi di tecnologia Meccanica. [Monografia/Trattato scientifico]
Gatto, Andrea; S., Oliva; A., Secciani Alfredo; G., Villani
abstract

Il sistema produttivo nazionale sta vivendo un momento di trasformazione, indotto dalla presenza di nuovi competitori internazionali che hanno il loro punto di forza nel basso costo di produzione e in una politica aggressiva, sostenuta spesso dai governi nazionali; contemporaneamente anche il mondo dell’istruzione è in fase di trasformazione e di ripensamento delle figure che costituiscono il "prodotto" delle scuole secondarie. Un testo destinato al futuro tecnologo deve tenere presente questi due aspetti ed essere integrato e aggiornato con le informazioni inerenti le innovazioni tecnologiche, la modernizzazione degli impianti, la meccanizzazione e l’informatizzazione delle operazioni, con un costante adeguamento alle norme di unificazione. La necessità di soddisfare le esigenze sopra espresse ha portato a una modifica dell’opera che, pur rimanendo salda nella sua struttura essenziale, risulta ampliata in numerose parti. Contemporaneamente sono stati snelliti altri capitoli che presupponevano un numero di ore d’insegnamento e di studio sicuramente esuberante rispetto alla formazione complessiva che lo studente deve raggiungere, o che trattavano argomenti che, pur conservando una certa valenza didattica, risultavano tecnologicamente superati.Nell’affrontare alcuni problemi e aspetti specifici della tecnologia è stata utilizzata una metodologia operativa tesa a evidenziare la necessità di un approccio "integrale", con il ricorso a conoscenze fornite specialmente dalla fisica e dalla chimica. Ogni capitolo inizia con un indice grafico per facilitare "l’orientamento e la navigazione" all’interno delle tematiche trattate, e si conclude con una scheda, strutturata su dieci quesiti, che costituisce un sistema di autovalutazione da parte dello studente.

2006 - Critical Evaluation of Indentation Fracture Toughness Measurements with Vickers Indenter on Ceramic Matrix Composite Tools [Articolo su rivista]
Gatto, Andrea
abstract

The evaluation of fracture toughness of advanced ceramic matrix composites (CMC) may be expensive if performed using conventional techniques (notch, long and short pre-cracks methods using the three or four point bending fracture test). The use of cracking during the indentation technique is ideally suited for toughness evaluation on a comparative basis and its result appears to provide a method for classifying CMC tools, according to their potential, as cutting tool materials having both high hardness and good crack resistance.The mechanism that leads to the higher fracture toughness of the composite are not yet fully understood. A number of toughening mechanisms such as crack deflection, crack branching, whiskers pullout, bridging (governed by interracial properties), and microcracking have been suggested in the literature, but there is still an ongoing debate about the relative importance of each of these mechanisms. Some authors believe that crack deflection is the main toughening mechanism: it occurs in materials containing anisotropically shaped grains or reinforcements. Crack deflection results when a crack front interacts with a second phase and changes its propagation direction, altering the fracture mode from pure mode I. Other authors suggest that in the crack wake bridging zone, whisker pull out is the major contributor in toughening.In this paper, the effective weight of indentation size effect (ISE), post indentation slow crack growth, material anisotropy and toughening mechanisms are critically evaluated.The CMC tools investigated were: SiCw/Al2O3; TiC/Al2O3; ZrO2/Al2O3. The fracture toughness measurements were performed considering the total crack length (summing all cracks visible on the surface) and the results were compared with those obtained in accordance with the Japanese Industrial Standard JIS R 1607.

2006 - Il colore dell’oro e altro [Articolo su rivista]
Gatto, Andrea
abstract

n.d.

2006 - Preliminary Studies of the Rapid Microwave Sintering of Green Parts Made of 420L Stainless Steel [Relazione in Atti di Convegno]
Veronesi, Paolo; Leonelli, Cristina; Denti, Lucia; Gatto, Andrea; L., Iuliano
abstract

Electromagnetic field distribution during microwave sintering ofmetal compacts, obtained by MIM or SLS was performed, evidencing afavourable necking stage promoted by local electric field concentrationamong the spherical particles. Microwave heating tests on 420L stainlesssteel cylindrical (20 mm diameter; 20 mm height) green parts obtained bySLS showed the possibility of achieving rapid sintering in single modeand multimode applicators operating at 2.45 GHz, in less than 20 minutes.The sintered parts, however, depending on the microwave heatingconditions, can present sensitisation due to the formation of chromiumcarbides, favoured by the C abundance provided by the decomposing organicbinder. This phenomenon constitutes a lower limit to the overall sinteringtime of the examined SLS green parts, which can be overcome only alteringthe sintering atmosphere or performing a preliminar de-binding step

2006 - Produzione Metalmeccanica [Monografia/Trattato scientifico]
Gatto, Andrea; G., Villani; A., Secciani
abstract

Il sistema produttivo nazionale sta vivendo un momento di trasformazione, indotto dalla presenza di nuovi competitori internazionali che hanno il loro punto di forza nel basso costo di produzione e in una politica aggressiva, sostenuta spesso dai governi nazionali; contemporaneamente anche il mondo dell’istruzione è in fase di trasformazione e di ripensamento delle figure che costituiscono il "prodotto" delle scuole secondarie. Un’opera destinata al futuro tecnologo deve tenere presente questi due aspetti ed essere integrata e aggiornata con le informazioni inerenti le innovazioni tecnologiche del mondo produttivo, particolarmente rilevanti negli ultimi anni. La necessità di soddisfare le esigenze sopra espresse ha portato a una modifica dell’opera che, pur rimanendo salda nella sua struttura essenziale, risulta ampliata in numerose parti, come nella trattazione della metrologia con l’introduzione delle macchine di misura a coordinate, del taglio non convenzionale (laser, plasma, getto d’acqua, elettroerosione a filo), della struttura delle moderne macchine utensili e arricchita con nuove figure. Contemporaneamente sono stati snelliti altri capitoli che presupponevano un numero di ore d’insegnamento e di studio sicuramente esuberante rispetto alla formazione complessiva che lo studente deve raggiungere, o che trattavano argomenti che, pur conservando una certa valenza didattica, risultavano tecnologicamente superati; inoltre sono state eliminate le numerose note che costituivano un "appesantimento" nella lettura del testo.Nell’affrontare alcuni problemi e aspetti specifici della tecnologia è stata utilizzata una metodologia operativa tesa a evidenziare la necessità di un approccio "integrale", con il ricorso a conoscenze fornite specialmente dalla fisica e dalla chimica, e sono stati introdotti alcuni paragrafi storici miranti ad aprire una collaborazione culturale con l’area delle materie letterarie. Ogni capitolo inizia con un indice grafico per facilitare "l’orientamento e la navigazione" all’interno delle tematiche trattate, e si conclude con una scheda, strutturata su dieci quesiti, che costituisce un sistema di autovalutazione da parte dello studente.

2005 - New developments in steel formulations for Direct Laser Sintering: characterization and evaluation of joining mechanisms. [Relazione in Atti di Convegno]
Bassoli, Elena; Gatto, Andrea; Iuliano, L.
abstract

Rapid Prototyping and Tooling are playing a more and more important role in the achievement of compressed time-to-market solutions. Even so, the spread of these techniques is hardly supported by scientific knowledge about the micro-mechanisms ruling the macroscopic performances of the part. In the present research, parts produced by Direct Laser Sintering technique have been studied, using Direct Steel 20 and the innovative Direct Steel H20. The research aimed at investigating the sintering mechanisms and their influence on the failure modes and mechanical performances. Tensile specimens have been produced, with different orientations in regard to laser path, to study the effect of laser sintering strategy on the anisotropy of parts per-formances. The tensile tests results have been correlated to the SEM observation of the specimens rupture sur-faces. The results proved that no anisotropy can be noticed in the mechanical response for loads applied in the different directions within the plane of powder deposition.

2005 - Rapid Casting in the development of an automotive component: evaluation of dimensional performances [Working paper]
Gatto, Andrea; Bassoli, Elena; L., Iuliano; M. G., Violante
abstract

Rapid Prototyping techniques can guarantee great competitive advantages if applied to the production of tools and moulds for the realisation of technological prototypes or pre-series.In the field of metal casting, innovative low-cost techniques have extended Rapid Casting possibilities, based on the 3 dimensional printing technology making use of a ceramic material. Complex cavities can be obtained quickly directly from the CAD model, complete of cores and air vents, which are suitable for casting light alloys. The process performances in terms of dimensional accuracy and surface finish still have to be evaluated.The research regarded the development and production of a metal prototype by means of an innovative rapid casting technique, referred to an aluminium casing for the automotive field. Initially CAE tools were applied to model the casting process, achieving the concurrent product-process development. Then, a technological prototype was obtained by rapid casting, using the ZCast technique. The metal prototype was measured on a CMM machine to calculate the dimensional tolerances ensured by the proposed technological chain.

2005 - Rapid Casting in the development of an automotive component: evaluation of dimensional performances. [Relazione in Atti di Convegno]
Gatto, Andrea; Bassoli, Elena; Iuliano, L.; Violante, M. G.
abstract

Rapid Prototyping techniques can guarantee great competitive advantages if applied to the production of tools and moulds for the realisation of technological prototypes or pre-series.In the field of metal casting, innovative low-cost techniques have extended Rapid Casting possibilities, based on the 3 dimensional printing technology making use of a ceramic material. Complex cavities can be obtained quickly directly from the CAD model, complete of cores and air vents, which are suitable for casting light alloys. The process performances in terms of dimensional accuracy and surface finish still have to be evaluated.The research regarded the development and production of a metal prototype by means of an innovative rapid casting technique, referred to an aluminium casing for the automotive field. Initially CAE tools were applied to model the casting process, achieving the concurrent product-process development. Then, a technological prototype was obtained by rapid casting, using the ZCast technique. The metal prototype was measured on a CMM machine to calculate the dimensional tolerances ensured by the proposed technological chain.

2005 - Sgrossatura e finitura, i materiali difficili da lavorare [Articolo su rivista]
Iuliano, L.; Gatto, Andrea
abstract

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2005 - Use of Selective Laser Sintering for the Production of Personalized Fixtures for Free Form Elements Ispection [Relazione in Atti di Convegno]
Iuliano, L; Minetola, P; VIOLANTE M., G; Gatto, Andrea
abstract

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2005 - Valutazione delle prestazioni dimensionali della tecnologia spin casting con stampi al silicone [Articolo su rivista]
Gatto, Andrea; Ferretti, A.
abstract

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2004 - "Reverse Engineering: potenzialità e applicazioni", Atti del Convegno sulla R.E., 2004, Università degli Studi di Modena e Reggio Emilia, DIMeC, Modena, 25 maggio 2003 [Curatela]
Andrisano, Angelo Oreste; Gatto, Andrea
abstract

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2004 - An innovative procedure to update moulds CAD model with the real geometry using Reverse Engineering [Relazione in Atti di Convegno]
L., Iuliano; P., Minetola; Gatto, Andrea; Bassoli, Elena
abstract

Modern CAD/CAM techniques together with 5 axis high speed milling allow to reduce moulds manufacturing time and costs. Nevertheless, in order to use the moulds, operations of manual finishing and fitting are still always required. Such operations, performed manually by mould makers, modify milled surfaces of the moulds. Changes in the product's shape are sometimes decided after the mould has already been machined. In such cases, if it's possible, the mould maker modifies directly the mould. The final real geometry of the mould does not coincide with the one of the original CAD model. The aim of this paper is to define a procedure, based on Reverse Engineering methods, to reconstruct and to update the mathematical model of the mould after it has been polished and fit. The procedure was tested on a mould for the production of a camera body. A zone of the mould was manually polished and an aesthetical change, not included in the original CAD model, was introduced on it directly. The mould was digitized with an optical system based on structured light and the point clouds were treated with a software for the reconstruction of the surfaces. After updating the CAD model of the mould, a conceptual prototype of the camera shell was created to appraise on the final product the aesthetical change directly introduced on the mould.

2004 - Characterisation of Innovative Materials for Direct Laser Sintering. [Relazione in Atti di Convegno]
Bassoli, Elena; Gatto, Andrea; Iuliano, L.; Atzeni, E.
abstract

Rapid Prototyping and Tooling are playing a more and more important role in the achievement of compressed time-to-market solutions, where prototype parts and tools are produced directly from the CAD model. In particular, Selective Laser Sintering (SLS) of metal powders with liquid phase is frequently applied for the production of inserts for injection moulding of plastic parts.An experimental campaign has been planned to investigate the surface finish and mechanical performances of Direct Laser Sintering technique, with particular regard to the effect of the laser sintering strategy on the anisotropy of the final part. Tensile specimens of DirectMetal 20 and DirectSteel 20 materials have been produced, with different orientations in regard to laser path. Rupture surfaces after the tensile tests were observed at the SEM, in order to understand failure mechanisms, whereas the observation of polished sections helped investigating joining phenomena between the particles. The proposed experimental methodology allowed correlating the macroscopic performances to the micro-mechanisms ruling the process, proving that no considerable differences can be noticed between samples produced in the X and Y direction within the plane of powder deposition.

2004 - Complex virtual models development for didactic purposes in the medical field [Relazione in Atti di Convegno]
Consolo, Ugo; Bortolini, Sergio; Landini, Barbara; Gatto, Andrea; Pellicciari, Marcello; Leali, Francesco
abstract

The many advantages in the availability of a virtual model of human parts regard, first of all, an easier shape comprehension of complex models in which different parts can be independently visualized and manipulated. The research job regards the virtual reconstruction of a maxillary arch physical model, through a reverse engineering approach. Thanks to the combination of laser scanning and mechanical touching, it was possible to obtain a CAD model in which all the teeth, the bone and the soft tissues can be independently viewed, moved and modified. The results can be applied for an improved communication between teachers and students, for a better comprehension of the inner correlation between different elements, and doctors and patients to the rapid overcoming of the initial cultural barrier. The research represents the first step of a fertile collaboration between engineering and medical staff, towards the implementation of innovative technological tools in human centred application, also in the field of virtual and augmented reality.

2004 - Design for manufacturing of an ergonomic joystick handgrip [Relazione in Atti di Convegno]
Bassoli, Elena; Gatto, Andrea; L., Iuliano; Leali, Francesco
abstract

A Reverse Engineering- (RE) and Rapid Prototyping- (RP) based approach to the development of a joystick handgrip with ergonomic features has been elaborated. The integration of Time Compression Techniques and Computer Aided Tools lead to a time-saving procedure for the design of a product whose ergonomic quality directly descends from users’ sensations of comfort. The CAD model availability throughout the progressive steps of product development ensured all the potentialities of Concurrent Engineering, while Computer Aided Engineering (CAE) simulation on the definitive geometry allowed to close the Computer Integrated loop to the manufacturing process.

2004 - Direct Laser Sintering of Metal Parts: Characterisation and Evaluation of Joining Mechanisms. [Relazione in Atti di Convegno]
Bassoli, Elena; Gatto, Andrea; Iuliano, L.; Atzeni, E.
abstract

The performances achieved by Rapid Prototyping techniques are progressively leading towards Rapid Manufacturing, that is the capability to produce end products, directly from the CAD model. Even so, the diffusion of these techniques is hardly supported by scientific knowledge about the micro-mechanisms ruling the macroscopic performances of the part. In the present research, mechanical performances of new materials produced by Direct Laser Sintering technique have been studied: a Polyamide and an innovative Polyamide-Aluminium composite (Alumide). Specimens were produced with different orientations in regard to powder deposition plane and laser path, to investigate how the manufacturing anisotropy affects the part performances.

2004 - Direct Laser Sintering of metal parts: characterisation and evaluation of joining mechanisms [Working paper]
Bassoli, Elena; Gatto, Andrea; L., Iuliano; E., Atzeni
abstract

Rapid Prototyping and Tooling are playing a more and more important role in the achievement of compressed time-to-market solutions, where prototype parts and tools are produced directly from the CAD model [1- 8]. In particular, Selective Laser Sintering (SLS) of metal powders with liquid phase is frequently applied for the production of inserts for injection moulding of plastic parts.On the basis of the deep knowledge developed by the authors on the solid-state process [1-4], an experimental campaign has been planned to investigate the surface finish and mechanical performances of Direct Laser Sintering technique. In particular, the research objective was to evaluate the effect of the laser sintering strategy on the anisotropy of the final part. Tensile specimens of DirectMetal 20 and DirectSteel 20 materials have been produced, following the specifications of standard ASTM E8, with different orientations in regard to laser path. Rupture surfaces after the tensile tests were observed at the SEM, in order to understand failure mechanisms, whereas the observation of polished sections helped investigating joining phenomena between the particles. The proposed experimental methodology allowed correlating the macroscopic performances to the micro-mechanisms ruling the process, proving that no considerable differences can be noticed between samples produced in the X and Y direction within the plane of powder deposition.

2004 - Direct Laser Sintering of metal parts: characterisation and evaluation of joining mechanisms [Relazione in Atti di Convegno]
Bassoli, Elena; Gatto, Andrea; L., Iuliano; E., Atzeni
abstract

Rapid Prototyping and Tooling are playing a more and more important role in the achievement of compressed time-to-market solutions, where prototype parts and tools are produced directly from the CAD model [1- 8]. In particular, Selective Laser Sintering (SLS) of metal powders with liquid phase is frequently applied for the production of inserts for injection moulding of plastic parts.On the basis of the deep knowledge developed by the authors on the solid-state process [1-4], an experimental campaign has been planned to investigate the surface finish and mechanical performances of Direct Laser Sintering technique. In particular, the research objective was to evaluate the effect of the laser sintering strategy on the anisotropy of the final part. Tensile specimens of DirectMetal 20 and DirectSteel 20 materials have been produced, following the specifications of standard ASTM E8, with different orientations in regard to laser path. Rupture surfaces after the tensile tests were observed at the SEM, in order to understand failure mechanisms, whereas the observation of polished sections helped investigating joining phenomena between the particles. The proposed experimental methodology allowed correlating the macroscopic performances to the micro-mechanisms ruling the process, proving that no considerable differences can be noticed between samples produced in the X and Y direction within the plane of powder deposition.

2004 - Planning and manufacturing a mould for Resin Transfer Moulding [Relazione in Atti di Convegno]
Iuliano, L; VIOLANTE M., G; Bassoli, Elena; Gatto, Andrea
abstract

Resin transfer moulding (RTM) is a low pressure moulding process, where a resin, mixed to a catalyst, is injected into a closed die, which vacuum has been obtained, containing a reinforcing pre-formed fibre [1, 2]; this fibre can be glass, carbon, aramidic fibre or a mixture of them. The resin and the catalyst are injected by a pump into a mixing head and then into the closed mould. When the resin is solidified, the die is opened and the piece is extracted [3, 4].Our study deals with the planning and the manufacturing of a low-cost modular die to be used in the resin transfer moulding (RTM) and it analyzes the costs and benefits of the suggested innovative solution.

2004 - Plasma Transferred Arc deposition of powdered high performances alloys: process parameters optimisation as a function of alloy and geometrical configuration [Articolo su rivista]
Gatto, Andrea; Bassoli, Elena; M., Fornari
abstract

The deposition of high wear- and corrosion-resistant alloys through Plasma Transferred Arc (PTA) is an easily automated process combining the possibility to obtain very thick coatings with high deposition speeds, low thermal distortion of the part and negligible dilution levels, thanks to a very high energy-concentration [S. Kalpakjian, S.R. Schmid, Manufacturing Engineering and Technology-4th edition, Addison-Wesley Publishing, 2001, p. 789-790, Scripta Materialia 37 (1997) 721, Applied Surface Science 201 (2002) 154, Surface and Coatings Technology 71 (1995) 196, Journal of Materials Processing Technology 128 (2002) 169, M. Bonacini, Plasma ad arco trasferito per riporti saldati con superleghe in polvere, Saldatura e taglio termico verso il 2000 IIS Meeting, October 3rd 1998, Milan-Italy, Wear 250 (2001) 611, Wear 249 (2002) 846, Composites Science and Technology 58 (1998) 299]. Literature studies regard mostly wear or high temperature behaviour of the deposited alloys and plasma hardening treatment without powder [Applied Surface Science 201 (2002) 154, Surface and Coatings Technology 71 (1995) 196, Journal of Materials Processing Technology 128 (2002) 169, M. Bonacini, Plasma ad arco trasferito per riporti saldati con superleghe in polvere, Saldatura e taglio termico verso il 2000 IIS Meeting, October 3rd 1998, Milan-Italy, Wear 250 (2001) 611, Surface and Coatings Technology 106 (1998) 156, Wear 249 (2002) 846, Surface and Coatings Technology 92 (1997) 157, Wear 181-183 (1995) 8 10, Wear 225-229 (1999) 1114], rather than an optimisation of process parameters, also in critical geometric configurations. An experimental campaign has been carried out on the deposition of two nickel- and a cobalt-base superalloys: Hastelloy 276, Inconel 625 and Stellite 6. Benchmarks of C-Mn steel have been chosen to test geometrical configurations that are critical for the application (corners and grooves). Specimen characterisation through liquid penetration inspection, optical- and scanning electron microscopy and microhardness tests proved that process parameters optimisation depends only on the geometrical configuration and not on the deposited alloy. This result suggests the importance of an accurate design of the reciprocal positioning and movement between the torch and the part to be coated, as a function of the deposition geometry.

2004 - Reverse engineering methodologies applied to complex virtual models development in the medical field [Relazione in Atti di Convegno]
Andrisano, Angelo Oreste; Bassoli, Elena; Gatto, Andrea; Leali, Francesco; Pellicciari, Marcello
abstract

Negli ultimi anni si è assistito, nell’ambito della ricerca applicata, ad un progressivo processo di trasferimento delle pratiche e delle metodologie tipiche dell’ingegneria industriale in ambito medicale, ed alla costituzione di gruppi di lavoro eterogenei, formati sia da personale medico che tecnico-ingegneristico. In particolare, sembra essersi affermata la tendenza alla definizione di modelli ed ambienti virtuali, ad esempio, per la pianificazione pre-chirurgica degli interventi e per la comprensione delle problematiche ad essa inerenti, e sembra progressivamente essersi diffusa la consapevolezza che sfruttando l’elevato contenuto informativo delle rappresentazioni grafiche tridimensionali è possibile favorire il superamento delle normali barriere culturali e comunicative, soprattutto tra medici e pazienti o tra insegnanti e studenti e creare gruppi di lavoro in grado di comunicare più facilmente e, quindi di raggiungere risultati migliori in tempi ridotti. Il presente lavoro di ricerca, realizzato grazie alla forte sinergia tra il gruppo di Disegno e Metodi dell’Ingegneria Industriale e il gruppo di Tecnologia e Sistemi di Lavorazione del Dipartimento di Ingegneria Meccanica e Civile di Modena, riguarda la definizione di una procedura che, attraverso l’uso combinato di differenti tecnologie di reverse engineering e di strumenti software dedicati alla generazione ed alla modellazione delle superfici, consenta di ottenere un prototipo virtuale complesso di un oggetto fisico. Il benchmark adottato, fornito dal Dipartimento di Neuroscienze, Testa-Collo, Riabilitazione di Modena è costituito dall’arcata mascellare di un modello artigianale scomponibile, formato da una base in resina e legno e da 14 denti in resina completamente estraibili, che, inserito in un apposito articolatore insieme alla corrispondente arcata mandibolare, viene attualmente utilizzato per descrivere la normale occlusione in ambito didattico. Il metodo sviluppato, basato sull’uso di strumenti hardware e software di costo medio basso, ha consentito di definire una procedura rapida e facilmente implementabile anche da parte di personale non tecnico, facilitando l’accostamento alle potenzialità offerte dalle tecnologie assistite da calcolatore per la realizzazione di prototipi virtuali.

2004 - Valutazione delle prestazioni dello stampaggio a iniezione assistito da gas e acqua [Articolo su rivista]
Gatto, Andrea
abstract

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2003 - A time compression approach for styling design [Relazione in Atti di Convegno]
M., Germani; F., Mandorli; Gatto, Andrea; Bassoli, Elena; F., Piatto; N., Tulloch
abstract

n.d.

2003 - Employment of Step Milling for the Manufacturing of Moulds for Resin Transfer Moulding for Infusion [Relazione in Atti di Convegno]
L., Iuliano; M., Ravera; M. G., Violante; Gatto, Andrea
abstract

-

2003 - Impact of time compression techniques on spotlight production [Relazione in Atti di Convegno]
L., Iuliano; Gatto, Andrea
abstract

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2003 - Microwave assisted sintering of SLS green metal parts [Relazione in Atti di Convegno]
Veronesi, Paolo; Leonelli, Cristina; Bassoli, Elena; Gatto, Andrea; L., Iuliano
abstract

Microwave assisted post-treatment of selective laser sintered green metal parts proved to be a new, fast and efficient way to densify complex-shaped elements, suitable for near-net-shape and net-shape manufacturing. Electromagnetic field modelling on pressed samples of RapidSteel 2.0 helped in choosing the proper experimental set up, using either single mode or overmoded microwave applicators operating at 2.45 GHz ISM frequency. LaserForm SLS green parts were exposed to high intensity microwave fields, using different lining configurations. Samples were characterized in terms of densification behaviour and microstructure: SEM observation of fracture and lapped surfaces allowed to analyse failure mechanisms and sintering degree.

2003 - Planning And Manufacturing A Mould For Resin Transfer Moulding [Relazione in Atti di Convegno]
L., Iuliano; Gatto, Andrea; M., Ravera; M. G., Violante
abstract

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2003 - Reverse Engineering approach for a joystick handgrip re-styling with ergonomic features [Relazione in Atti di Convegno]
Bassoli, Elena; Gatto, Andrea; L., Iuliano; G., Marchiandi
abstract

Ergonomics plays a more and more important role in product development, ensuring a better quality of life and work and also contributing to enrich the product image. If the importance of an ergonomic design is commonly recognized, no stated procedures for the development of an ergonomic product are still available. This is probably due to the fact that ergonomics is a qualitative subjective characteristic, that can’t be reduced to a list ofspecifications. In agreement with the opinion that a product can be defined ergonomic only in reference to a precise target of users and for a definite application [1], this paper regards aninnovative user-based procedure for the re-styling of a commercial handgrip. The proposed procedure, combining traditional modeling and Time Compression techniques, guarantees the time- and cost-saving development of a product ensuring comfort of use and minimizing pressure concentrations on the user’s hand [2] that can be defined ergonomic since it directly derives from users’ physical characteristics.

2003 - Selective Laser Sintering Of Metal Parts:Comparison Of Two Material Systems [Relazione in Atti di Convegno]
L., Iuliano; Gatto, Andrea; Bassoli, Elena; E., Azteni; M. G., Violante
abstract

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2003 - Selective Laser Sintering: An Evaluation Of The Performances Of Sand Sintered Components [Relazione in Atti di Convegno]
E., Atzeni; R., Ippolito; L., Iuliano; Gatto, Andrea
abstract

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2003 - Una soluzione italiana per la produzione additiva di modelli per fonderia [Articolo su rivista]
Gatto, Andrea
abstract

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2003 - Valutazione e integrazione di Sistemi PDM [Articolo su rivista]
Gatto, Andrea; F., Pirini; L., Iuliano; G., Marchiandi
abstract

n.d.

2003 - “La funzione trasversale della Reverse Engineering e il suo Ruolo Strategico”, Atti del I e II Convegno sulla R.E., 2002 e 2003, Università degli Studi di Modena e Reggio Emilia, DIMeC, Modena, 12 giugno 2003 [Curatela]
Andrisano, Angelo Oreste; Gatto, Andrea
abstract

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2002 - Applicazione dell'elettroformatura di Cu nel Rapid Manufacturing. [Relazione in Atti di Convegno]
Gatto, Andrea; Iuliano, L.
abstract

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2002 - I materiali per la fabbricazione degli stampi [Capitolo/Saggio]
Gatto, Andrea; F., Rabezzana
abstract

n.d.

2002 - La Francia che non Conosci, Cronaca di un Viaggio nella Prototipazione e Dintorni [Articolo su rivista]
Gatto, Andrea
abstract

n.d.

2002 - Lavorazioni meccaniche [Capitolo/Saggio]
F., Rabezzana; L., Iuliano; Gatto, Andrea
abstract

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2002 - Misura, controllo, collaudo [Capitolo/Saggio]
Gatto, Andrea; L., Iuliano
abstract

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2002 - Soluzioni alternative nell'industria motociclistica [Articolo su rivista]
Gatto, Andrea
abstract

n.d.

2001 - An Innovative Technique For On-Line Control Of Selective Laser Sintering System [Relazione in Atti di Convegno]
L., Iuliano; Gatto, Andrea
abstract

n.d.

2001 - Application of Rapid Tooling for Sheet Metal Forming: Flexible Drawing Die With Punches Built by SLS Technique and by Copying Process [Relazione in Atti di Convegno]
Gatto, Andrea; L., Iuliano
abstract

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2001 - Effect of the Post Curing Process Parameters Choice on Part Produced by Direct Croning Process [Relazione in Atti di Convegno]
Gatto, Andrea; L., Iuliano
abstract

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2001 - Evaluation of Inserts for Modular Thermoplastic Injection Moulds Produced by Spin Casting [Articolo su rivista]
Gatto, Andrea; L., Iuliano
abstract

Concurrent engineering enables a company to speed up its time to market: rapid prototyping forms a part of this approach. The term rapid tooling (RT) refers to the rapid creation of tools in much the same way as RP means the rapid creation of models. It is a method that offers both designers and manufacturers attractive advantages in the form of time compression and cost reduction. In an era of automated manufacturing the prototype can be produced layer by layer directly from a 3D CAD model using rapid prototyping (RP) techniques [Rapid prototyping and manufacturing, fundamental of stereolithography, SME, Dearborn, MI, 1992; Layer Manufacturing a Challenge of the Future, Tapir Publisher, Trondheim, Norway, 1992]. The drawback is that only a limited number of RP technologies cater for metal parts and taking the top three positions of vendors into account (Stratasys, 3D Systems, Sanders), their systems have no access to metal prototypes [Rapid prototyping, state of the industry report 1998, SME, Dearborn, MI, 1999]. Several RT techniques can be employed to save time in the manufacturing of plastic injection moulds: thermal spraying; quick casting, electroplating, direct metal sintering. These techniques have been subject to intensive study for a number of years and their extensive commercial potential makes them attractive propositions. Major advances in technology makes spin casting a fully proven tool for manufacturing and prototyping functional components. This paper describes the employment of spin casting for the construction of mould inserts in standard, commercial-grade pressure die casting zinc.

2001 - Rapid Manufacturing by Copper Electroplating [Relazione in Atti di Convegno]
Gatto, Andrea; Iuliano, L.
abstract

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2001 - Step Milling for Prototyping og Large & Precise Parts [Relazione in Atti di Convegno]
Gatto, Andrea; L., Iuliano; G., Marchiandi
abstract

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2000 - Design for Manufacturing: Laser Beam Welding of Centrifugal Machine Components [Relazione in Atti di Convegno]
F., Mandorli; M., Germani; Gatto, Andrea; S., Berti
abstract

n.d.

2000 - L’alluminio va veloce [Articolo su rivista]
Gatto, Andrea; Picchio, P.; Marra, P.; Marra, L.
abstract

n.d.

2000 - Micro joining mechanisms between metal particles in the sls technique [Relazione in Atti di Convegno]
Gatto, Andrea; L., Iuliano
abstract

n.d.

1999 - Application of Rapid Tooling for Sheet Metal Forming [Relazione in Atti di Convegno]
Gatto, Andrea
abstract

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1999 - Bond Strength of Four Cements related to Complex and Monoaxial Tensile Stress [Abstract in Atti di Convegno]
E., Accarisi; C., Mazzi; Gatto, Andrea; F., Sampalmieri; G., Albergo
abstract

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1999 - Così Nasce lo Stampo di Imbutitura [Articolo su rivista]
Gatto, Andrea; C., Brubi; A., Bravetti; R., Mancini
abstract

n.d.

1999 - Employment of Laminate Tooling Techniques for Moulds Fabrication [Relazione in Atti di Convegno]
L., Iuliano; Gatto, Andrea
abstract

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1999 - Evaluation of Inserts for Modular Thermoplastic Injection Moulds Produced by Spin Casiting [Relazione in Atti di Convegno]
Gatto, Andrea; L., Iuliano
abstract

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1999 - Il Rapid Tooling nell’imbutitura di lamiere [Articolo su rivista]
Gatto, Andrea; C., Bruni; A., Bravetti; ., Mancini
abstract

n.d.

1999 - Manufacturing of EDM Electrodes with Rapid Tooling Techniques [Relazione in Atti di Convegno]
Gatto, Andrea; L., Iuliano
abstract

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1999 - Non Conventional Characterisation of Stereolitographic Parts [Relazione in Atti di Convegno]
Gatto, Andrea; L., Iuliano; G., Tosi; D., Pocci
abstract

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1999 - Valutazione Degli Stampi In Lega Di Alluminio Per La Produzione Di Componenti Con Alte Caratteristiche Superficiali [Relazione in Atti di Convegno]
Gatto, Andrea; Marra, P.; Marra, L.
abstract

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1998 - Advance in both Rapid Prototyping & Rapid Tooling Techniques [Relazione in Atti di Convegno]
Iuliano, L.; Settineri, L.; Gatto, Andrea
abstract

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1998 - Comparaison of rapid tooling techniques for moulds and dies fabrication [Relazione in Atti di Convegno]
Gatto, Andrea; Iulianol,
abstract

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1998 - High-speed turning and drilling experiments on metal matrix composites [Articolo su rivista]
Iuliano, L.; Settineri, L.; Gatto, Andrea
abstract

quick tool wear and premature failure are usual in the machining operations of metal matrix composite (MMC); such phenomena occur due to the presence of hard abrasive ceramic component which increases the mechanical characteristics. In the present paper the cutting performances of high rake angle carbide tools and of their diamond coated versions are compared in the high-speed lathe-turning of an Al2O3/Al 6061 MMC. Furthermore, the results of some drilling experiments are reported, carried out with HHs drills and their TiN coated versions. The influence of the cutting parameters, in particular cutting feed and speed, on tool wear and surface finish has been investigated. the higher abrasion resistance of the coatings results in increased tool life performances and different chip formation mechanisms.

1998 - High-speed turning and drilling experiments on metal matrix composites [Relazione in Atti di Convegno]
Iuliano, L; Settineri, L; Gatto, Andrea
abstract

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1998 - High-speed turning experiments on metal matrix composites [Articolo su rivista]
Iuliani, L.; Settineri, L.; Gatto, Andrea
abstract

The hard abrasive ceramic component which increases the mechanical characteristics of metal matrix composites (MMC) causes quick wear and premature tool failure in the machining operations. The aim of the paper is to compare the behaviour of high rake angle carbide tools with their diamond coated versions in high-speed machining of an Al2O3Al 6061 MMC. The influence of the cutting parameters, in particular cutting feed and speed, on tool wear and surface finish has been investigated. The higher abrasion resistance of the coatings results in increased tool life performances and different chip formation mechanisms.

1998 - PROTOTIPAZIONE RAPIDA LA TECNOLOGIA PER LA COMPETIZIONE GLOBALE [Monografia/Trattato scientifico]
Gatto, Andrea; Iuliano, L.
abstract

n.d.

1998 - Particles’ formation and deposition in the Sanders RP process [Relazione in Atti di Convegno]
Gatto, Andrea; Iuliano, L.; Settineri, L.
abstract

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1997 - Advance in Two Stage Shearing [Relazione in Atti di Convegno]
Iuliano, ; G., Perotti; A., Barcellona; F., Micari; Gatto, Andrea
abstract

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1997 - Advanced Coated Ceramic Tools for Machining Superalloys [Articolo su rivista]
Gatto, Andrea; Iuliano, L.
abstract

The main limitation on the use of nickel-base superalloys, such as INCONEL 718, is the difficulty in conventional-type machining. The use of high cutting speed to achieve both machining adiabatic conditions and high productivity is necessary for their applications. This non-conventional type machining results in a short life-span of tools, even for those expensive ceramic ones with reinforced SiC whiskers (SiCw) suitable for use at high cutting speeds. The aim of the paper is to present the results of a new idea proposed by the authors to obtain an increase in tool life at high cutting speed by minimizing the temperature effects on composite reinforcement mechanisms. The 2090 SiC whiskers reinforced A12O3 tools were CrN and (Ti,AI)N coated using the PVD technique, and comparative machining tests on INCONEL 718 were carried out using uncoated and coated tools. After machining, the tools were observed with a scanning electron microscope (SEM), and EDAX (X-ray) semiquantitative analyses were performed. The behaviour of the CrN and (Ti,AI)N layers using various cutting conditions was analysed and different wear mechanisms along the tool chip contact length were observed. The cause and the mechanisms of wear were deduced and mathematic models linking tool life with process parameters were suggested.

1997 - Comparison of rapid prototyping techniques for plastic injection moulds [Relazione in Atti di Convegno]
Gatto, Andrea; Ippolito, R.; Iuliano, L.
abstract

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1997 - Cutting Mechanisms and Surface Features of WED Machined MMCs [Articolo su rivista]
Gatto, Andrea; Iuliano, L.
abstract

Metal matrix composites are manufactured in a variety of grades and forms, but machining is usually necessary to obtain finished engineering components. The presence of the hard reinforcing ceramic makes these materials difficult for conventional machining. Wire electro discharge machining (WEDM) is used for the processing of heat-treated high-quality alloys or for the machining of complex shapes in advanced materials. This paper describes WEDM tests performed under one roughing and two finishing conditions on two composites, SiC/2009Al alloy with 15% whiskers and with 20% particles reinforcement. Some roughed and some finished surfaces were glass-bead peened. To understand the reinforcement and the behaviour of the matrix during the machining of both composites, the machined surfaces, their sections and profiles were examined by scanning electron microscopy, and energy dispersive semi-quantitative analyses of X-rays were also carried out. The surface roughness for the process parameters used are indicated.

1997 - Fresatura di un composito 10%Al2O3/Al606: Meccanismo di Formazione del Truciolo e Modello di Previsione della Vita dell’Utensile [Relazione in Atti di Convegno]
Benelli, M.; Gatto, Andrea; Iuliano, L.
abstract

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1997 - High-Speed Turning Of Metal Matrix Composites With Coated And Uncoated Carbide Tools [Relazione in Atti di Convegno]
Iuliano, L.; Settineri, L.; Gatto, Andrea
abstract

-

1997 - High-Speed Turning Of Metal Matrix Composites With PCD Coated Carbide Tools [Relazione in Atti di Convegno]
Ippolito, R.; Settineri, L.; Iuliano, L.; Gatto, Andrea
abstract

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1997 - Investigation on Rapid Tooling Techniques for moulds & Dies Fabrication [Relazione in Atti di Convegno]
Iuliano, L.; Gatto, Andrea; Carosi, A.; Pocci, D.
abstract

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1997 - La PR amica degli elettrodi [Articolo su rivista]
Gatto, Andrea; Iuliano, L.
abstract

n.d.

1997 - Manufacturing of plastic injection moulds using stereolithography EDM electrodes [Relazione in Atti di Convegno]
Carosi, A.; Pocci, D.; Ippolito, R.; Iuliano, L.; Gatto, Andrea
abstract

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1997 - On the Performance of a CrN Coated SiC Whiskers Reinforced Ceramic Tool for High Speed Machining of Ni-Base Super-Alloys [Articolo su rivista]
Felloni, L.; Gatto, Andrea; Ippolito, R.; Iuliano, L.
abstract

n.d.

1997 - Tensile tests, thermal measurements and photoelasticity observations of specimens produced by stereolithography technique [Relazione in Atti di Convegno]
Gatto, Andrea; Ricci, R; Ippolito, R.; Iuliano, L.
abstract

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1996 - Edm tooling by solid freeform fabrication and electroplating techniques [Relazione in Atti di Convegno]
Ippolito, R; Iuliano, L; Gatto, Andrea
abstract

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1996 - Employment of Metal Matrix Composites in Automotive Industry: a Case Study [Relazione in Atti di Convegno]
R., Ippolito; L., Iuliano; A., Balestrini; A., Fuganti; Gatto, Andrea
abstract

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1995 - Benchmarking of rapid prototyping techniques in terms of dimensional accuracy and surface finish [Articolo su rivista]
Iuliano, L.; Ippolito, R.; Gatto, Andrea
abstract

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1995 - High Speed Turning of Metal Matrix Composites with Tools of Different Material and Geometry [Relazione in Atti di Convegno]
Gatto, Andrea; Iuliano, L.; Tagliaferri, V.
abstract

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1995 - Integrating reverse engineering, rapid prototyping and investment casting in the jeweller’s craft [Relazione in Atti di Convegno]
Iuliano, L.; Ippolito, R.; Gatto, Andrea
abstract

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1995 - Metallisation and Rapid Tooling [Relazione in Atti di Convegno]
Iuliano, L.; Gatto, Andrea; DE FILIPPI, A.
abstract

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1995 - Power Input in High Performance grinding [Relazione in Atti di Convegno]
Ippolito, R.; Iuliano, L.; Felloni, L.; Gatto, Andrea
abstract

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1994 - COMPOSITO CERAMICO PER SUPERLEGHE NI [Articolo su rivista]
Gatto, Andrea; Iuliano, L.
abstract

n.d.

1994 - Chip Formation Analysis in High Speed Machining of a Nickel Base Superalloy with Silicon Carbide Whisker-Reinforced Aluminia [Articolo su rivista]
Gatto, Andrea; Iuliano, L.
abstract

High speed turning tests were performed on a heat resistant alloy (Inconel 718), using SiC (20%) whiskers reinforced ceramic tools. The main aims of these tests were the following: (1) mapping cutting speed-feed and machined volume in order to find a region free from tool breakage; (2) analysing tool wear and chip formation mechanisms; and (3) from the experimental results modelling analytically both chip formation processes and tool wear mechanism. Tool and chip were observed at the SEM and EDAX semiquantitative analyses were carried out to evaluate micro-welds on the chip and areas of welded or scattered material over the tool. Micro-hardness mapping was carried out on the longitudinal cross-section of the chips to monitor its dependence by process parameters. Variable wear mechanisms along the tool-chip contact length that were attributed to variations in plastic deformation energy were observed. There variations were analytically modelled in orthogonal cutting conditions. Longitudinal and tranverse shear planes into the chip were also observed. The causes and the mechanisms of wear, chip formation and the hardening of work material were deduced. The presence of whiskers pull out mechanisms due to temperature effects in the tool-chip interface were also observed.

1994 - Chip formation analysis in high speed machining of a nickel base superalloy with silicon carbide whisker-reinforced alumina [Articolo su rivista]
Gatto, A.; Iuliano, L.
abstract

High speed turning tests were performed on a heat resistant alloy (Inconel 718), using SiC (20%) whiskers reinforced ceramic tools. The main aims of these tests were the following: (1) mapping cutting speed-feed and machined volume in order to find a region free from tool breakage; (2) analysing tool wear and chip formation mechanisms; and (3) from the experimental results modelling analytically both chip formation processes and tool wear mechanism. Tool and chip were observed at the SEM and EDAX semiquantitative analyses were carried out to evaluate micro-welds on the chip and areas of welded or scattered material over the tool. Micro-hardness mapping was carried out on the longitudinal cross-section of the chips to monitor its dependence by process parameters. Variable wear mechanisms along the tool-chip contact length that were attributed to variations in plastic deformation energy were observed. There variations were analytically modelled in orthogonal cutting conditions. Longitudinal and tranverse shear planes into the chip were also observed. The causes and the mechanisms of wear, chip formation and the hardening of work material were deduced. The presence of whiskers pull out mechanisms due to temperature effects in the tool-chip interface were also observed. © 1994.

1994 - Investigation on Machining Conditions for WEDM of Nickel Base Superalloys [Relazione in Atti di Convegno]
Gatto, Andrea; Iuliano, L.
abstract

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1994 - L'USURA AD ALTA VELOCITA' [Articolo su rivista]
Felloni, L.; Gatto, Andrea; Ippolito, R.; Iuliano, L.
abstract

n.d.

1994 - On the Performances of Drills in the Machining of Aeronautical Materials [Relazione in Atti di Convegno]
Gatto, Andrea; Forlin, G.; Iuliano, L.
abstract

-

1994 - Performances of coated ceramic tools for high speed machining of Ni-base superalloys. [Relazione in Atti di Convegno]
Gatto, Andrea; Iuliano, L.
abstract

-

1994 - Surface Finish of metal Matrix Composites Under High Speed Turning [Relazione in Atti di Convegno]
Ippolito, R.; Iuliano, L.; Gatto, Andrea; Tagliaferri, V.
abstract

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1994 - WED Machinability of a 25% Silicon carbide particle Reinforced 6061 Al Alloy Composite [Relazione in Atti di Convegno]
Felloni, L.; Gatto, Andrea; Iuliano, L.; Ippolito, R.
abstract

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1993 - High speed machining of Ni-based superalloys: tool wear pattern and chip features. [Relazione in Atti di Convegno]
Gatto, Andrea; Iuliano, L.
abstract

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1993 - Meccanismi di Usura di Utensili Ceramici Rinforzati con Whiskers di SiC nalla Lavorazione ad Alta Velocità di Inconel 718 e Acciaio C40 [Relazione in Atti di Convegno]
Felloni, L.; Gatto, Andrea; Ippolito, R.; Iuliano, L.
abstract

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1993 - Produzione di Sferette da Lega Amorfa Mediante Tecnologia Laser [Relazione in Atti di Convegno]
Covelli, L.; Felloni, L; Tagliaferri, V.; Gatto, Andrea
abstract

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1992 - Fish processing wastewater: Emission factors and high load trickling filters evaluation [Relazione in Atti di Convegno]
Battistoni, P.; Fava, G.; Gatto, A.
abstract

An Italian seafood factory processing frozen fish and fresh clams was investigated. Specific water consumption (SC) and pollutant emission factors (EF) are evaluated. Results evidence high SC values, in the range 18-74 l/Kg, due to defrost and extensive washing and cleaning practised; EFs appear high although not directly comparable with data reported by other authors. Two high-rate trickling filters, cross flow (CF) and vertical flow (VF), are examined over a two years period. Results suggest a pseudo half-order kinetic reaction with a superior performance of CF plastic media. From the elaboration of the experimental data a semiempirical correlation between specific surface removal (SSR) and operative parameters is obtained.

1992 - High load trickling filters. Biofilm accumulation and sludge production [Relazione in Atti di Convegno]
Battistoni, P.; Fava, G.; Gatto, A.
abstract

A pilot-scale investigation was carried out to evaluate the parameters affecting biofilm accumulation and sludge production. The behaviour of a cross flow (CF) plastic medium filter (4.3 m3 of Plasdek B 27) was followed over an eight month period. Four hydraulic loadings, from 2.5 to 3.6 m3/m2h, (organic loadings from 1.5 to 6.2 Kg BOD5/m3d) were experimented. Medium temperature, BOD5 influent and hydraulic loading were determinants for biofilm accumulation and sludge production. The specific oxygen uptake rate (SOUR) of waste sludge was found related to inlet BOD5. Furthermore a relationship between median retention time (MRT) and filter biomass was obtained; this relationship gave also a good capacity to interpret MRT for low-rate filters.

1991 - Fatigue fracture of AISI 4340 DVM steel in gaseous hydrogen & effect of tempering temperature [Articolo su rivista]
Casagrande, A.; Felloni, L.; Fratesi, R.; Gatto, A.; Ruggeri, O.
abstract

The effect of dry hydrogen (p = 102 kPa at room temperature) on AISI DVM austenized at 1113 K and tempered at 463, 53 and 743 K has been investigated by means of determinations of fatigue crack growth rate (FCGR) using CT samples (L-R and C-L orientation) precracked in laboratory air up to a value of ΔK of about 11 MPa√m. The fatigue tests were conducted both in air (RH = 45-50%) and hydrogen environment under the following conditions: R = 0.2, Pmax = 2.5 kN, sine wave of 3 and 0.5 Hz. The FCGR were found to be independent on the frequency. The fracture surface of samples fatigated in air, showed brittle striations and, at higher ΔK, some transgranular fracture, while in those obtained in dry hydrogen both an increasing percentage of quasi-cleavage facets and secondary cracks were observed. The fatigue behaviour of the specimens tempered at 463 and 553 K in the two environments considered was much diversified. The fracture surfaces revealed a mixed fracture mode: intergranular along the grains of primary austenite and in some zones, transgranular. The da/dN - ΔK curves showed that the FCGR was controlled by a condition of stress corrosion cracking. A KISCC value of 13.7 MPa√m was estimated. The appearance of a plateau in these curves, at nominal increasing ΔK, is presumably attributable to a slowing of the primary cracking owing to the occurrence of an increasing number of secondary cracks.