Research on multi-stage deep drawing with electro-permanent magnet technology

Abstract

Nowadays, the application of highly efficient forming techniques has been paid great attention to multi-stage sheet metal forming. In this work, the deep drawing of a circular sheet with stainless steel 304 into a cylindrical contour is performed via electro-permanent magnetic (EPM) multi-stage forming (EPMIF). Applying Lorenz force generated by directional moving electric charges, EPMIF is a hybrid forming process that combines a quasi-static stamping technique and EPM actuators to form a workpiece. During the process of EPMIF, the optimal feed increment value is designed theoretically and confirmed experimentally, which is unequal spacing and gradually decreasing for better forming performance. Excellent formability of the sheet can be observed without significant rapture and wrinkling defects, in detail, the relative forming height of the metal slab could reach 0.65. Furthermore, under different feed increments, the evolution law of metal sheet deformation is investigated by common evaluation indices including forming height, strain distribution, and thinning ratio. Meanwhile, the microscopic structure of the workpiece is compared with the simulated profile. The result shows that the deep drawing with EPMIF is conducive to improving the forming performance of metal sheets and avoiding the fracture induced by uneven deformation at the same time.