Numerical and Experimental Studies on the Demolding of Injection Molding Parts

Abstract

Numerical and experimental studies are conducted on the demolding stage of injection molding process. Based on an integrated computer-aided-engineering software package, a numerical approach has been proposed to predict the ejection force and to analyze the layout of ejector pins. The predictions are validated in this work by injection molding of polycarbonate boxes. The boxes are molded at given processing condition while ejected with different layouts of ejector pins. The ejection force is measured by load transducers installed behind the ejector pins. The shrinkage of the boxes is also measured by displacement transducers. It is found that the measured total ejection force and its distribution over the pin layouts compare reasonably well with numerical predictions. The validation is also supported by the agreement between the predicted and measured warpage of the boxes. Additional results are provided for a complex molding geometry for which the mold opening and ejection operations need to be considered in studying the demolding.