Design and Validation of Additively Manufactured Injection Molds

The injection molding process is only economical with large batch sizes due to expensive tools that cannot be used variably. Additively manufactured tools made of plastic could reduce manufacturing costs and represent an alternative to conventionally manufactured tools for prototype applications as well as enabling small series with the injection molding process. The aim of this article was to examine additively manufactured injection molding tools; to determine their potential in terms of service life, surface quality, and production time; and to link them with the production costs so that the profitability can be assessed. Therefore, a reference component and an injection mold have been designed. To test the capabilities of different 3D printing techniques and materials, three molds have been produced by fused filament fabrication (FFF), one by PolyJet process, one by digital light processing, and for a direct comparison to conventional methods, one mold has been milled from aluminum. All molds have been tested in two series. First, they were used under the same conditions over a period of 100 injection molding cycles. Based on the knowledge obtained and an additional profitability analysis, three forms could be identified as promising. Two of these forms could be further investigated in a second series of tests. Based on all experiments, the technical feasibility of additively manufactured injection molds for small batch production could be confirmed. It could be evaluated that each manufacturing process and every material has some advantages and disadvantages. On the one hand, temperature-resistant thermoplastics can be processed with FFF, which can withstand service lives of more than 150 cycles without any signs of wear and are therefore suitable for small series. On the other hand, the PolyJet process achieves good surface qualities and short production times, which means that it can be used for prototype applications.