EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Additive manufacturing is gaining importance in the medical field. One of the main drawbacks of additive manufacturing is the lower mechanical performance compared to the bulk material. However, mechanical properties can be improved by doing parameter optimization. This was done for two additive manufacturing technologies such as the ARBURG plastic freeforming (APF) and the Fused Filament Fabrication (FFF) process. The APF uses a small injection molding unit for melting thermoplastics pellets and a discharge unit that forms droplets. The droplets are deposited on a movable platform to build a part layer-by-layer. Due to the deposition of droplets instead of strings, different process settings are used, e.g., the drop aspect ratio (DAR). The DAR is the ratio between the drop´s height and width and affects the printing paths. In additive manufacturing, processing profiles can either be optimized for geometrical accuracy or mechanical properties; thus, a compromise between profiles must be defined for each application. It is crucial to determine the parameters with the highest impact on mechanical properties. Therefore, a design of experiments (DoE) was used to find these parameters for a medical-grade poly(methyl methacrylate). The DAR, nozzle temperature and chamber temperatures were varied for the APF process. The extrusion multiplier, the extrusion temperature and building platform temperature were analyzed for the FFF process. Different mechanical tests were performed on printed parts. The results indicate that for FFF, the extrusion temperature has the highest impact, while for APF, the DAR has the highest impact. For both methods, the tensile strength was found to be strongly related to the density. Thus, the density must be maximized to get the highest mechanical properties possible.