Effect of As-Mold Rapid Cooling on Shrinkage and Morphology of Core Region of Injection Molded Parts Using Microcellular Foaming Process

Abstract

Shrinkage is a common problem in injection molded parts which considerably affects the dimensional accuracy of the product. In this paper normal cooling (NC) and as-mold rapid cooling (RC) of core region of injection molded samples have been used to study the% shrinkage of Acetal copolymer with increased weight reduction using Microcellular Foaming Process (MCPs). The results show that shrinkage reduction is not only associated with weight reduction (WR) but also directly related with the decrease in crystalline phase and as-mold RC rate.14% decrease in linear shrinkage by NC with 5.5% loss in crystallinity and 24% decrease in linear shrinkage with 9% loss in crystallinity with RC were observed at 10% weight reduction at same mold temperature. Furthermore, RC of core region resulted into decreased cells size and increased cells density. The study can be useful to control the dimensional tolerances and morphology of the injection molded parts by RC of still molten core region.