2019 Volume 60 Issue 703 Pages 241-246
The surface quality and shape of an extruded part of a workpiece were investigated in cold backward cup extrusion with torsional oscillation. In this extrusion process, a cylindrical aluminum workpiece lubricated with a mineral oil was simultaneously extruded in the axial direction and twisted in the circumferential direction between extrusion and knockout punches with a maximum axial speed of 0.1 mm/s, an alternating amplitude of 5°, and a maximum angular speed of 0.5 rpm at room temperature. The deformation behavior of the workpiece at the inner surface of the container was investigated by experiment and finite element simulation. The sidewall of the workpiece was axially extruded and circumferentially rotated with approximately 25% lower contacting pressure with the container, so that an extruded workpiece with a uniform and smooth sidewall surface was obtained. Furthermore, the circumferential profile of the sidewall height of the extruded workpiece was close to uniform because the workpiece was uniformly lubricated by the circumferential rotation of the workpiece. The influence of the non-uniform friction at the container-workpiece contact on the sidewall height of the extruded workpiece was discussed using the results of finite element simulation.