Low-cost metal-forming process using an elastic punch and a reconfigurable multi-pin die

Due to the need for low-cost tooling and quality parts, a new technique has been developed which brings together the benefits of both multi-point forming (MPF) and rubber-pad forming. A significant disadvantage of MPF is the time required to adjust the heights of the pins in the upper and lower matrices and align the tools. Rubber forming achieves flexibility by replacing one of the MPF pin matrices by an elastic punch. In this study, polyurethane (PU) rubber with a Shore hardness of A90 was adopted as the elastic punch material. The punch was combined with a reconfigurable MPF die to reduce both tool cost and time to set the pins to produce doubly curved parts of acceptable quality. Experimental work has been carried out to confirm the validity of the new technique. Finite element modelling (FEM) using the ABAQUS software was applied to study stress distribution numerically in the formed parts at the end of the forming process. The amounts of wrinkling and springback were employed as criteria to evaluate the quality of the formed part and to compare the results of the current (semi-MPF) approach against full-MPF results. The major outcomes of this study were time and cost reductions of at least 50% with the added benefits that there is a significant decrease in wrinkling and springback in the final formed part even without using a blank holder.