Modeling of the Injection Molding Process Coupled with the Fast Mold Temperature Evolution

Abstract

The modulation of mold temperature during injection molding is a strategic issue since it allows modulating/calibrating interesting properties of the moldings. In this work, thin heating devices were layered on the cavity surface allowing its fast temperature evolution between injection and cooling channels temperatures. The heating devices were made by a conductive layer between two insulating layers with thicknesses selected in order to realize a heating/cooling cycle as fast as possible. Several tests were performed, injecting polypropylene (iPP), using different heating powers and heating times to analyze the effect of the fast cavity surface temperature evolution on the molding morphology and properties. The heat transfer through the mold was modeled, accounting for the Joule effect in the conductive layer of the heating devices. To validate the proposed modeling of the heat exchange during the process, the simulated temperature evolutions at the polymer–cavity and the heating device–mold interfaces were satisfactorily compared with the experimental ones recorded during the tests conducted adopting different mold temperature evolutions. Furthermore, pressure evolutions during the process recorded in different position along the flow path were satisfactorily compared with the simulated ones to validate the predictions of the thermo–mechanical histories experienced by the polymer.