A simplified approach to predict part temperature and minimum “safe” cycle time

The largest component of the injection molding cycle is the cooling time. Thus it is highly desirable, to be able to predict what its minimum acceptable value can be. This is becoming even more important with increased competition from regions where the labor cost is low. In an injection molding operation, the mold thermal state changes from its initial value until a quasi steady state is reached. The minimum required cooling time increases with continuous molding until a steady state value is achieved. Improving the mold thermal design will decrease the cooling time thus reducing total cycle time. The overall goal of this work is to develop a simple reliable method to predict a minimum safe cycle time for steady production. In this article, we discuss software capable of simulating the thermal state of the part and mold for multiple injection molding cycles while balancing simulation time with results accuracy. Three case studies are presented, one done in our labs and two on‐site at an automotive manufacturing facility. The three case studies are used to evaluate the ability of the software to predict part surface temperature for continuous molding. We also discuss how this software can be used as the basis to establish the minimum safe cycle time. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers