Surrogate-based multi-point forming process optimization for dimpling and wrinkling reduction

Multi-point forming (MPF) has been gaining attention for use in flexible sheet metal forming, since it is conducive to the manufacture of various shapes. However, discrete punch elements may induce either dimples or wrinkles, resulting in defective products. To address these forming issues, this study aims to eliminate both dimpling and wrinkling by adjusting parameters such as the punch speed, punch pressure (cushion compressive strain ratio), and elastic cushion thickness through multi-objective optimization. Evaluation of dimpling and wrinkling under variation in these three MPF parameters benefits from ordinary Kriging for computational efficiency. Multi-objective optimization with a genetic algorithm is used to determine the Pareto fronts of the dimpling and wrinkling measures, and a technique for order preferences by similarity to ideal solution (TOPSIS) is performed for identifying the best candidate among the Pareto optima. Finally, a dimpling-and-wrinkling-free TOPSIS solution is numerically verified by comparison with results of a full model simulation and experimentally validated by its application to a manufactured product.