Multi-objective optimization of variable packing pressure profile and process parameters in plastic injection molding for minimizing warpage and cycle time

Process parameters in plastic injection molding (PIM) such as the packing pressure, the melt temperature, and the cooling time have a direct influence on the product quality. It is important to determine the optimal process parameters for high product quality. In addition to the product quality, high productivity is required to plastic products. This paper proposes a method to determine the optimal process parameters in the PIM for high product quality and high productivity. A constant packing pressure during the PIM is conventionally used, but the variable packing pressure profile that the packing pressure varies in the packing phase is adopted as the advanced PIM. Warpage and cycle time are taken as the product quality and the productivity, respectively. Then, these are simultaneously minimized and the pareto-frontier between them is identified. Numerical simulation in the PIM is so intensive that a sequential approximate optimization using radial basis function is adopted. It is found through the numerical result that the variable packing pressure profile can improve both the warpage and the cycle time, compared with the conventional PIM approach. In order to examine the validity of the proposed approach, the experiment is carried out. It is confirmed through the numerical and experimental results that the proposed approach is valid for minimizing the warpage and the cycle time.