Abstract
Material extrusion (MEX) of metallic powder-based filaments has shown great potential as an additive manufacturing (AM) technology. MEX provides an easy solution as an alternative to direct additive manufacturing technologies (e.g., Selective Laser Melting, Electron Beam Melting, Direct Energy Deposition) for problematic metallic powders such as copper, essential due to its reflectivity and thermal conductivity. MEX, an indirect AM technology, consists of five steps—optimisation of mixing of metal powder, binder, and additives (feedstock); filament production; shaping from strands; debinding; sintering. The great challenge in MEX is, undoubtedly, filament manufacturing for optimal green density, and consequently the best sintered properties. The filament, to be extrudable, must accomplish at optimal powder volume concentration (CPVC) with good rheological performance, flexibility, and stiffness. In this study, a feedstock composition (similar binder, additives, and CPVC; 61 vol. %) of copper powder with three different particle powder characteristics was selected in order to highlight their role in the final product. The quality of the filaments, strands, and 3D objects was analysed by micro-CT, highlighting the influence of the different powder characteristics on the homogeneity and defects of the greens; sintered quality was also analysed regarding microstructure and hardness. The filament based on particles powder with D50 close to 11 µm, and straight distribution of particles size showed the best homogeneity and the lowest defects.
Highlights
Additive manufacturing (AM) has gained a great amount of interest in the past two decennia for various fields of applications [1]
This process for 3.2. Three-Dimensional (3D) object shaping is based on fused deposition modeling (FDM), but filament manufacturing is similar to powder metal extrusion process (PEP) and powder injection moulding (PIM)
PEP/PIM, the parts produced by Material extrusion (MEX) use filaments with a high volume percentage of vol.% [10,11,12], and need two subsequent steps: debinding, to promote binder removal, and metals particles, typically between 50 and 65 vol.% [10,11,12], and need two subsequent steps: sintering, to attain a dense 3D object (Figure 1)
Summary
Additive manufacturing (AM) has gained a great amount of interest in the past two decennia for various fields of applications [1]. When applied to the mixing of metallic/ceramic powder particles and organic binder and/or additives based on polymers, it has adopted the standardised name of MEX [2,3,4,5,6] This process for 3D object shaping is based on FDM, but filament manufacturing is similar to powder metal extrusion process (PEP) and powder injection moulding (PIM). The according the available literature, scientific studies on have investigated influencethe of properties of steel and copper powder oblige a detailed ofcopper these powder the application of MEX technology for the production ofanalysis densified parts, inparticles. A complete understanding of all five steps involved in the manufacturing process—namely, mixing the constituents of the filaments (copper powder, binder, and additives), extrusion (filament manufacturing), strands for shaping (3D objects), debinding (binder removal), and sintering (powder particle consolidation)
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