Effects of Injection Molding Parameters on the Production of Microstructures by Micropowder Injection Molding

Micropowder injection molding (mu PIM) is a potential low-cost process for the mass production of metal or ceramic microstructures. In order to obtain good molded microstructures and to avoid molding defects, it is important to select suitable injection molding parameters. In this paper, the selection of injection molding conditions for the production of 316L stainless steel microstructures by mu PIM is presented. Silicon mold inserts with 24 x 24 microcavities were injection molded on a conventional injection molding machine. The dimensions of each microcavity were Phi 100 mu m x depth 200 mu m, giving an aspect ratio of 2. The distance between each microcavity was 200 mu m. Five sets of experiments were conducted by varying one injection molding parameter at a time. The parameters included injection pressure, holding pressure, holding time, mold temperature, and melt temperature. Higher injection pressure and holding pressure were required during the injection molding process due to the small dimensions of the microcavities and the large number of microcavities (576 microcavities). High mold temperature was required for complete filling of the microcavities. Molded microstructures without visual defects were obtained using appropriate injection molding parameters. Catalytic debinding and sintering of the 316L stainless steel microstructures were successfully conducted.