Numerical investigation of warpage in insert injection-molded lightweight hybrid products

In this study, a numerical investigation of warpage found within insert injection-molded frame parts was carried out based on the Taguchi method in conjunction with a response surface methodology. An integrated mold frame unit was recently developed by integrating a conventional mold frame, metal reflector, and bezel together, to be used in a back light unit system of a liquid crystal display. Such an integrated plastic-metal hybrid part could be successfully manufactured through the insert injection molding process. However, minimization or even elimination of warpage, one of the severe defects found in injection-molded products, is required for reliable mass production. Therefore, a numerical analysis was performed to reveal the effects of the relevant processing parameters, showing that packing pressure played the most significant role, originated from temperature difference between corners of the final product. Furthermore, a double optimization process combining the Taguchi method and the response surface methodology was employed to determine accurate and optimal processing conditions. The results clearly verified that the current combination technique can overcome the Taguchi method's limitation, resulted from a discrete optimization nature, and also effectively give more accurate optimum solutions without complicated algorithms and software.