Numerical shape optimization as an approach to reduce material waste in injection molding

Reducing material waste is a major issue during new product development, especially for injection-molded parts, where the wall thickness has a strong influence on molding times and therefore on the manufacturing cost. Finding the minimum material amount for producing high-quality products is a difficult and time-consuming task using state-of-the-art computer-aided engineering CAE tools. In this study, a numerical procedure is presented to reduce the material amount required for injection-molded parts by optimizing their wall thickness distributions with respect to part quality and identifying an upper limit for the injection pressure. The closed-loop procedure consists of three main parts: (1) a mesh parameterization tool for manipulating the thickness distribution of the part, (2) a mold flow analysis for evaluating the producibility and part quality, and (3) a genetic algorithm for adjusting the design variables toward minimum material waste. The effectiveness of the procedure is demonstrated into two different industrial parts. Using the part volume as the main objective, reductions in material waste of approximately 25 to 30 % can be achieved via a slight improvement in part warpage compared to the initial design. Considering part warpage as an additional objective results in reductions in material waste of 12 to 17 %, these reductions in waste are accompanied by substantial improvements in part quality.