Investigation of Flash Generation Process for Engineering Plastic by Flash Generation-Evaluating Mold

Abstract

Flash is an appearance defect that arises in injection molding. In this paper, a flash generation-evaluating mold developed by the authors was improved to evaluate the ease of occurrence of flashes in resins, such as engineering plastic, molded at high mold temperatures and melt pressures in the cavity. Using the improved mold, we evaluated the occurrence conditions of secondary flash in polyoxymethylene (POM), polyamide PA6 (nylon-6), and polycarbonate (PC). The secondary flash occurred most easily for PA6, second most easily for POM, and least easily for PC. A correlation between the ease of occurrence of secondary flash and the crystallization of the resin was also clarified.