Controlling non-uniform blank holder pressures in an extra-deep drawing process for enhancing formability and product quality

In this study, the focus is on investigating prevalent issues of rupture and wrinkling that occur during the extra-deep drawing process. These defects are very common in a local sanitary equipment industrial company, mainly in the manufacture of bathtubs, which increases scrap and leads to loss of time and costs in production. To analyze these defects, a numerical simulation of the bathtub extra-deep drawing process was performed with industrial parameters. The originality lies in controlling non-uniform blank holder pressures generated from six actuators in order to control the flow of the blank between the blank holder and the die and ensure the production of defect-free bathtubs. 3D and ultrasonic thickness measurements were performed on a bathtub manufactured without defects. Numerical and experimental plots of the thickness reduction show that the two approaches are in good agreement. The numerical results demonstrate that there are no rupture or wrinkling defects in the bathtub final shape, which exactly matches the actual case manufactured by the company. The numerical analysis was also performed on different cases that can cause rupture and wrinkling defects, namely: the influence of the blank holder pressure, the blank initial shape, and the die design using draw beads.