Metal-polymer Fused Deposition Modeling (FDM) can be used to develop metal parts with less cost and facilities. However, these 3D printers face issues of brittle filaments, nozzle clogging, rigorous post-processing stage, debinding and shrinkage. This work presents the right selection of raw materials and process optimization to fabricate 40:60 wt.% SS-PLA composite filament, using an in-house built filament extruder. Before FDM printing, flexibility of the filament has been improved by heat treating the filament in the oven at 45 °C for 6 hours. Filament has a cross section of \(\phi { }1.75 \pm 0.05 \;{\text{mm}}\) with uniformly distributed SS particles in the PLA matrix. However, during FDM printing of the composite part, issues as filament breakage and nozzle clogging are observed which led to the fabrication of weak and rough 3D structures. As the FDM printer parameters strongly depend on the rheological properties of the metal-polymer filament material, melt flow behavior in the extruder, and nozzle design. Therefore, to resolve the issue of improper printing of parts, melt flow analysis inside the liquefier is performed with the help of a mathematical model and pressure drop using CFD analysis in COMSOL, for SS-PLA melt. Mathematical model and Rheology analysis show that the increase in viscosity caused change in pressure drop in the liquefier and nozzle zone, causing poor printing quality of designed composite part. Melt Flow Behavior inside the liquefier, shows that 12 times higher compression force of \(F_{c}^{{{\text{metal}} - {\text{PLA}}}} = 1.4365 \times 10^{5} \;{\text{N}}\) is required to extrude SS-PLA filament compared to \(F_{C}^{{{\text{PLA}}}} = 1.6768 \times 10^{6} \;{\text{N}}\) that is needed for PLA extrusion. Using the optimized parameter obtained from the analysis viz. 473 K temperature, 3 mm/s feed rate and 0.8 mm nozzle diameter, smooth and dimensionally accurate SS-PLA composite part are successfully printed with the FDM printer.
