Optimization of Injection Mold Design Through Application of External Selective Induction Heating

Abstract

The aim of the presented research project is to optimize the injection mold for a better quality of thin-walled moldings without significant increase in cycle time, through application of external selective induction heating. The injection process of thin-walled parts is one of the most problematic procedures in plastics processing. Most commonly occurring defects of said parts are: short shots, diesel effect, welding lines, excessive internal stresses and warping. In order to reduce the number of these deficiencies, electromagnetic induction heating in concern with water cooling has been proposed to achieve rapid temperature cycling during the injection process. High-frequency induction is one of the most efficient methods of injection mold surface heating, by virtue of electromagnetic induction effect. The present study investigates selective induction heating of the cavity surface for three different thin-walled parts. Feasibility of the localized heating method was investigated through simulation of melt flow through the heated areas. The latter were selected on the basis of defects occurrence. To evaluate the applicability and efficiency of the induction heating process (within an area of 32×20 mm), a the plate with cooling channels and a movable heated insert were constructed. During the heating process, an inductor with a concentrator and a 10 kW generator. The measurement was performed by means of the Flir T620 thermographic camera and a Pt100 temperature sensor. Preliminary results allowed continuation of the experiment. For this purpose, an injection mold, consisting of three exchangeable cavity inserts on the stamp and matrix side, was assembled. In order to evaluate the applicability of induction heating, the injection process was carried out and its results were compared to those obtained through utilization of conventional means. The investigation showed that selective heating of the cavity surface to 150 °C afforded elimination of the majority of defects.