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A comprehensive review of extrusion-based additive manufacturing processes for rapid production of metallic and ceramic parts
Full text linkThe extrusion-based additive manufacturing (EAM) technique is recently being employed for rapid production of metals and ceramic components. This technique involves extruding the metal or ceramic material in solid powder form mixed with a binder (i.e., an expendable viscous fluid), which is removed from the part after 3D printing. These technologies rely on the large design freedom allowed and the cost efficiency advantage over alternative metal additive manufacturing processes that are based on high energy beams, such as laser or electron beams. The EAM of metals and ceramics is not yet widespread, but published scientific and technical literature on it is rapidly growing. However, this literature is still less extensive than that on the fused deposition modeling (FDM) of plastics or the selective laser melting (SLM) of metals. This paper aims at filling this gap. FDM and powder injection molding are identified as preceding or enabling technologies for EAM. This paper systematically reviews all aspects of the feedstock EAM processes used for production of complex-shaped parts. The unique characteristics and advantages of these processes are also discussed with respect to materials and process steps. In addition, the key process parameters are explained to illustrate the suitability of the EAM process for diverse application domains
Freeform 3D deposition of small diameter copper tubes using a powder-binder feedstock
Full text linkCopper is an interesting material for many applications including thermal management devices, which make often use of copper piping. This study proposes a method for the freeform deposition of a copper-binder feedstock, extruded through an additive manufacturing machine. Several tubes have been printed using a special nozzle and varying process parameters. The dimensional results of the deposited specimens at the green state and the physical properties of the tubes after debinding and sintering have been measured. The results demonstrate that piping in serpentine layout can be deposited by extrusion and sintered, even with sharp bends without significant ovalization of the cross-section
Towards a General Quality Indicator for Adaptive FEM Simulation of Sheet Forming Processes
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La misura della formabilità dei tubi per idroformatura: il “bulge test” dei materiali tubolari
No full textRapid surface quality assessment of green 3D printed metal-binder parts
No full textMixtures made of a solid metal powder and a viscous polymeric binder are increasingly used in material Extrusion Additive Manufacturing (EAM) processes. The EAM process adopts the relative movement of an extruder head to a build table, to deposit thin strands of the mixture and build a 3D object layer by layer. In this study, EAM process was applied to produce 3D printed square plate-shaped parts of stainless steel 316 L at the green state, i.e. before debinding and sintering. The 3D printing experiments were designed by considering various independent process parameters: extrusion velocity v e , table velocity v t , layer height h and hatch spacing D a . The surface characteristics of as printed (green) square plate-shaped parts were investigated by a rapid, high-resolution optical imaging technique. The obtained images were analyzed to model the effect of the process parameters on the surface uniformity Ui and space filling Fi. The proposed methodology can be also used as a process monitoring technique. The study has demonstrated that the layer height h has the most relevant effect on the infill quality and should be set at a low value for good quality. However, a combination of the other parameters can be found that yields a compromise between infill surface quality and build up rate
Flattening of bent metal sheets as a remanufacturing operation
Full text linkThe reshaping of end-of-life or scrap sheet metal panels is a potential remanufacturing process, which enables significant environmental benefits over the traditional metal recycling routes. This paper experimentally investigates cold and warm press flattening of waste sheet metal for enabling remanufacturing. Samples of stainless steel, aluminium alloy, and low carbon steel were bent to various internal angles using v-die air bending operations. Then, flattening tests were conducted with a hydraulic press, with tools capable of heating up to 300 °C. The process parameters included dwell force, dwell time, and tool temperature. The target final angle after load release is set at 180°, but the flattening process typically induces springforward, and the final angle is generally larger than 180°. Springforward can be mitigated by using warm flattening conditions with all the tested materials. It can also be reduced if superposing a steel mesh between the top flattening die and the sheet. The paper demonstrates and explains the mechanical effects of the flattening process
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