Study of Molded-in Stresses and Warpage Behavior in Injection-Compression Molded Parts

Injection-compression molding (ICM) is a process that results in reduction in molding pressure and the clamp force that is required to mold. Since the part experiences lower pressure gradient during molding, the residual stresses induced due to flow of material is reduced considerably. Due to this, and if everything else is kept constant, the final part warpage gets lowered significantly. This reduction in molded-in stresses also improves optical properties, which is important for applications requiring transparency. Also, ICM as a process is being used for molding of large parts, which otherwise require high tonnage presses to mold them. In this class, we investigate the influence of various parameters of the ICM process on final part warpage. The part considered here is a 2K molded part where the first shot can be molded using the conventional molding process. The second shot is injection-compression molded, keeping the first shot as a plastic insert.