Analysis of Radial Heat Transfer in an Injection Mold with Highly Dynamic Segmented Mold Tempering

Abstract

The demand for precise injection molded parts is continuously increasing. One of the main effects that negatively influence the geometrical part properties is warpage due to inhomogeneous shrinkage. By homogenizing the specific volume and thus the shrinkage potential, warpage is expected to be reduced. The following work addresses the homogenization of the specific volume by controlling the local part temperature with 18 individual tempering zones in the mold, which are capable of rapid heating and cooling.To control the tempering elements precisely, a model predictive control (MPC) approach has been developed, which predicts mold and melt temperature for each tempering zone based on a discretized one-dimensional heat transfer equation. Due to radial heat transfer processes in the mold cavity and the part, the temperature of one tempering zone is expected to have an influence on neighboring tempering zones. By additional consideration of the radial heat transfer in the mold and the part, the heating and cooling output of each tempering zone can be adapted according to the heat input from the neighboring tempering zones.To quantify the reciprocal thermal influence of the tempering zones, heating trials have been performed and recorded with a thermographic camera.KeywordsInjection moldingPrecision moldingMold temperingProcess controlPvT-optimizationModeling