Processability of metal-filament through polymer FDM machine

FDM is one of the simplest and cheapest available additive technologies, mostly limited to polymeric materials. Metal-FDM process may overcome this limit using a metal filament bounded with polymer, which is removed through debinding and sintering treatments. Producing metal components using an economic machine would make it possible to produce non-critical components with complex geometry at an industrial level and at low-cost. This work aims to investigate whether a low-cost commercial 3D printer may be able to print a metal filament and what are the achievable density and the shrinkage on the final part. An experimental campaign (24 factorial plan) was performed, considering as variable factors the nozzle temperature, the infill pattern, the print speed and the layer thickness. Statistical tools as the boxplot for determining outliers and the analysis of variance (ANOVA) were used to evaluate the results, identifying which process parameters ad their interactions affect the selected indicators (density and shrinkage). The results show that the conversion of a low-cost FDM machine from polymer to metal filament is possible, generating repeatable and stable results. The process is faster and less expensive than the existing powder-bed-fusion based metal AM technology. The best combination of printing parameters was identified considering as target point the density of the “traditional” AISI 316L steel. Different behaviors in terms of shrinkage were identified: trends are stable and very similar for X and Y directions, independently from the printing parameters, while the interaction between temperature and other parameters causes higher variability along the Z-axis.