Investigation on Process Characteristics and Application of Injection-Compression Molding Process

Abstract

Simulation and the associated numerical algorithm on the injection-compression molding (ICM) process were developed to understand processing characteristics by changing processing parameters including compression speed, switch time from injection to compression, compression stroke as well as initial cavity thickness and part thickness using disk parts. It was found that the compression speed and compression stroke are the two factors affecting the molding pressure most significantly. Switch time also shows apparent effect on the pressure profiles. Using lower switch time, lower compression speed and higher compression stroke will result in lower cavity pressures. The percentage reduction in molding pressure is higher if part becomes thinner when using ICM. The melt velocity far from the gate was found to be higher than that near the gate during the compression stage contrary to that of conventional injection molding (CIM) resulting in different part residual stress and melt temperature distribution. The simulated pressures for both ICM and CIM show good coincidence with those obtained from cavity pressure measurements. The advantages of injection-compression molded lens were demonstrated and compared with conventional injection molded lens.