Copper extrusion 3D printing using metal injection moulding feedstock: Analysis of process parameters for green density and surface roughness optimization

Abstract In the present study, the extrusion-based 3D printing process was explored using metal injection moulding (MIM) copper feedstock to fabricate dense copper parts. The influence of process parameters of 3D printing, namely layer thickness, nozzle speed, extrusion multiplier and extrusion temperature on green density and surface roughness were studied. Based on the central composite design method, a set of experiments was chosen to study the individual and interaction effects of parameters. Analysis of variance was performed to identify the significant factors and statistical models were obtained by regression analysis. The green density was observed to increase with varying the layer thickness from 0.25 to 0.05 mm and nozzle speed from 100 to 20 mm/s. Similarly, surface roughness was improved by decreasing the layer thickness and the nozzle speed and by increasing the extrusion multiplier up to a specific value. The extrusion temperature gave the best results at 200 °C for both green density and surface roughness. The significant interactions between the parameters for both green density and surface roughness were also studied. A multi-objective optimization approach was used to maximize the green density and minimize the surface roughness within the range of the parameters. Micro-tomography scans were used to analyze the porosity and voids in samples printed with optimized and non-optimized parameters. Besides, sintering was performed on the optimized printed sample to fabricate a dense copper part and analyze linear shrinkage during sintering. Sintered copper parts with high density and low surface roughness were obtained with the optimized printing process parameters.