Multi-objective optimization for minimizing weldline and cycle time in rapid heating cycle molding using variable packing pressure profile

Abstract

In plastic injection molding (PIM), weldline affects the strength and surface quality of products, and it is then important to determine the optimal process parameters for the weldline reduction. Rapid heat cycle molding (RHCM) that actively controls the mold temperatures is an effective PIM technology to weldline reduction, but requires long cycle time. In this paper, variable pressure profile that packing pressure varies during the PIM process is incorporated in the RHCM in order to shorten the cycle time. To determine the process parameters in the proposed RHCM, multi-objective design optimization is performed. The mold temperature is maximized for the weldline reduction, whereas the cycle time is minimized for high productivity. Numerical simulation in the proposed RHCM is computationally so expensive that sequential approximate optimization is used to identify the pareto-frontier. Based on the numerical result, the experiment using PIM machine (MS100, Sodick) is also conducted to examine the validity of the proposed RHCM.