Optimization of metallic powder filaments for additive manufacturing extrusion (MEX)

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.

Influence of Metallic Powder Characteristics on Extruded Feedstock Performance for Indirect Additive Manufacturing

“…For the development of a new copper filament for material extrusion (MEX), several feedstocks were developed using torque rheometry equipment. CPVC established was 61 vol.% [ 29 ]. Table 4 shows the final composition and density of each feedstock, with its associated torque.…”

“…Even so, the behaviour of the flexural modulus was very similar for the three different filaments. The high deflection at break and low flexural modulus was already established to be printable by [ 29 ].…”

“…Even so, the behaviour of the flexural modulus was very similar for the three different filaments. The high deflection at break and low flexural modulus was already established to be printable by [29]. After detailed analyses of the filament morphology, tensile tests (Figure 11) and flexural tests (Figure 12) were performed.…”

Searching New Solutions for NiTi Sensors through Indirect Additive Manufacturing

“…The evaluation of the critical powder volume concentration (CPVC) [ 24 , 25 , 26 ] methodology used in powder injection molding (PIM) feedstocks allows for the optimization of the NiTi filament composition (NiTi powder, master binder, and additives). A torque rheometer, Plastograph Brabender GmbH and Co. (Duisburg, Germany) with a rotation blade speed of 30 rpm at a temperature of 180 °C, was used to optimize the feedstock.…”

A Review on Material Extrusion Additive Manufacturing of Metal and How It Compares with Metal Injection Moulding

“…The rapid prototype of high wear resistance M2 steel can be fabricated with the in-house built filament, which can be an alternative for establishing a method for MIM part prototyping [96]. In addition, several end-user engineering parts have been commercially fabricated by the user-friendly closed metal MEX system [83,141]. The example of the end-user brake pedal 316L part is presented in Figure 25a.…”