Work in progress: use of wood‐based inserts in injection molding

Abstract

In the context of ever-shorter product development cycles and the necessary prototype development, the advantages of the injection molding process cannot be fully exploited because it is not possible to economically produce very small series. The aim of this study is to examine the suitability of soft tooling using wood-based mold inserts for small batch production in polymer injection molding. To this end, various types of wood are being tested in initial injection molding trials as part of this study, and their behavior under the process conditions is being compared. Those wooden molds are milled and tested in various injection molding tests. The produced parts as well as the used molds are then examined for wear, geometric accuracy and in terms of the tensile test specimen, for their load bearing capacity. It was shown that modified materials like laminated wood or compressed bamboo resist the loads of the injection molding process better than natural materials. Also, it was shown that the parts produced have a repeatable geometrical shape. After tool setup, it was possible to produce up to five consecutive workpieces of similar quality. Tensile tests showed reproducible strength values for ABS specimens while wood-fiber reinforced Polypropylene showed unpredictable behavior. Downsides of the new design approach are the longer cycle times which lead to material degradation and the fast wear of the wooden mold inserts.