Numerical Simulation of Forming a 3D Shape by a Multi-Point Die

Abstract

Multi-point forming (MPF) is considered one of the flexible and creative three-dimensional sheet metal forming processes. Such a technique replaces traditional rigid punches with a set of adjustable-height discrete pins. By altering the relative height of each pin, a variety of three-dimensional curved surfaces can be formed. In order to avoid changing the height of the pins manually, they are attached to springs. Hence, when a load applies at the pins holder, these will take the shape of the die due to the spring properties quickly and easily. However, wrinkles and dimples are inevitable issues that appear when using MPF. In order to investigate and minimize these defects, a finite element approach using ANSYS 15.0 software has been applied to perform numerical simulations for this MPF operation. Two cases have been examined in this study. Whilst the first one includes direct forming between the pins and the metal, a sheet of rubber has been added among them in the second case. The simulation has been conducted on brass (Cu Zn 65-35) with a thickness of (0.71 mm) and rubber with a thickness of (2 mm). The boundary conditions, which are attached to the blank, enable the motion in the y-direction only with respect to the lower profile at a depth of (30) mm, and was immobilized by constraints in the x and z direction. The study has shown remarkable results since the dimples were visible on the sheet surface in the first case, whereas these defects were significantly reduced during the second one. Moreover, the blank profile’s maximum stress and strain have been studied. Due to force distribution, rubber reduces maximum stress and strain to approximately 27% and 49%, respectively, in the second case