Numerical and experimental studies of injection compression molding process for thick plastic gas valve stem

Abstract

A crucial problem in injection molding of the thick plastic stem that is a key part of high-pressure gas valve is the formation of internal voids, because the structural failure of plastic stem owing to the internal voids not only deteriorates the operating function of gas valve but also may lead to the tremendous loss of financial and human resources. In this context, the goal of this study is to examine whether the formation of internal voids can be successfully suppressed when injection molding is replaced with injection compression molding. To examine this possibility, the major mold flow characteristics between injection molding and injection compression molding are firstly compared through 3-D thermal flow analyses. Next, for the sake of verification of numerical comparison, the plastic stem specimens are manufactured by both molding processes and the internal void formation is inspected using X-ray photos and cutting planes of specimens. Through the comparative numerical and experimental studies, it is confirmed that the crucial formation of internal voids in the conventional injection molding process can be successfully and completely removed by employing the injection compression molding.