Abstract
Additive manufacturing (AM) of metallic powder particles has been establishing itself as sustainable, whatever the technology selected. Material extrusion (MEX) integrates the ongoing effort to improve AM sustainability, in which low-cost equipment is associated with a decrease of powder waste during manufacturing. MEX has been gaining increasing interest for building 3D functional/structural metallic parts because it incorporates the consolidated knowledge from powder injection moulding/extrusion feedstocks into the AM scope—filament extrusion layer-by-layer. Moreover, MEX as an indirect process can overcome some of the technical limitations of direct AM processes (laser/electron-beam-based) regarding energy-matter interactions. The present study reveals an optimal methodology to produce MEX filament feedstocks (metallic powder, binder, and additives), having in mind to attain the highest metallic powder content. Nevertheless, the main challenges are also to achieve high extrudability and a suitable ratio between stiffness and flexibility. The metallic powder volume content (vol.%) in the feedstocks was evaluated by the critical powder volume concentration (CPVC). Subsequently, the rheology of the feedstocks was established by means of the mixing torque value, which is related to the filament extrudability performance.
Highlights
Additive manufacturing (AM) of powder metals and metal alloys is an unavoidable area for Industry 4.0 owing to its potential to address some of the most significant industrial challenges in the twenty-first century concerning parts/system/devices processing [1]
The present study is focused on the Material extrusion (MEX) technology, which was initially referred to as the fused deposition of metals (FDMet), and as Fused Filament Fabrication (FFF) or as Metallic Fused Filament Fabrication (MF3) [15]
MEX is based on the fused deposition modelling (FDMTM) technology commercialized by Stratasys Inc. for polymers and waxes, where the filament is composed of a mixture of a high volume content of metallic powders with organic constituents [16]
Summary
Material extrusion (MEX) and binder jetting (BJ) [11] are already well-established technologies with market acceptance for the AM Based on this successful background, MEX and BJ have been investigated with the aim to produce metallic and ceramic functional/structural components through shaping, debinding, and sintering (SDS). High-quality structural/functional parts/systems/devices through an SDS process must include efforts to achieve the highest content (vol.%) of the metallic powder particles possible in the feedstock within the steady-state regime but always taking into account the final mixing torque value. This becomes a significant challenge in MEX because the mixture must be manufactured in a filament form. The present study aims to contribute, whatever the powder selected, to high-quality filaments for MEX technology, that is in conjunction with binder jetting technology, the future of AM of functional/structural 3D metallic objects
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