PSI - Issue 41

Saveria Spiller et al. / Procedia Structural Integrity 41 (2022) 158–174 Saveria Spiller/ Structural Integrity Procedia 00 (2019) 000–000

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2. Feedstock preparation One of the main advantages of MEAM lies in the uncomplicated shaping process. The FDM printers are nowadays inexpensive and broadly available on the market. On the contrary, there is a small variety of commercial high-filled polymer filaments available, and as a consequence, it is common for researchers to prepare their feedstock material in-house . Indeed, this implies the considerable advantage of controlling more parameters affecting the process, since the characteristics of the feedstock have a direct impact on the subsequent phases of the process. For example, the average size of the metal powder affects the flowability of the filament, which in turn affects the printing process (Singh et al., 2020, 2021). The choice of the binder composition is likewise important to determine the debinding type and parameters. Finally, other characteristics such as the infill percentage affect the densification of the part, which is facilitated by a high content of the metal powder (Cerejo et al., 2021).

Fig. 1. Schematic illustration of the MEAM process with the three main phases of shaping, debinding, and sintering. Each phase corresponds to a different material composition.

As mentioned since the beginning, the feedstock material is usually in the shape of a filament. Nevertheless, other forms can be chosen for the feedstock material (Gonzalez-Gutierrez et al., 2018). For example, in a plunger based extrusion system, the feedstock is provided in the shape of rods. Alternatively, in the screw-based system, the material is in the shape of pellets (Fig. 2). Those options are preferred where the viscosity of the polymer-metal powder compound doesn’t allow the continuous extrusion of a long filament.

Fig. 2. Different types of extrusion (Gonzalez-Gutierrez et al., 2018)

According to Agarwala et al. (1996), a good filament should present several characteristics to ensure a smooth