Effect of processing parameter changes on mechanical properties during injection molding: Amorphous versus semi‐crystalline materials

Abstract Injection molding is the most common method to mass‐produce plastic parts. The high cost and long lead time of traditional injection molding steel molds make 3D‐printed plastic molds a potential substitute for limited production runs and prototype parts. However, results suggest that for some materials, utilizing plastic molds (compared to metal molds) could decrease the mechanical properties of parts, especially the ductility. In order to better understand the issues with utilizing plastic molds, in this work, we use a design of experiments to investigate how the processing parameter changes affect mechanical properties by comparing a semi‐crystalline polypropylene and an amorphous polystyrene material in a metal mold for better control of the controllable variables. Results show that ductility is the most sensitive property to processing conditions, especially for polypropylene. Our analysis shows that the controllable variable that affects ductility the most is mold temperature, then packing pressure, and injection time. Highlights 3D‐printed plastic molds is a potential substitute for limited production runs. Effects of processing parameters are analyzed through the design of experiments. Ductility is the most sensitive property to processing conditions for the material studied. Mold temperature is the most significant variable for ductility.