Reduction in Axial Extrusion Load by Torsional Oscillation in Cold Backward Cup Extrusion

Abstract

To reduce axial load in cold backward extrusion, torsional oscillation with a maximum frequency of 1.5 Hz around the extrusion axis was superposed with axial deformation. A cylindrical aluminum workpiece 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 5 rpm at room temperature. The relationship between the torsional oscillation conditions and the axial load was investigated in backward extrusion with reductions in cross-sectional area of 0.17-0.69. The maximum reduction in axial load was obtained with approximately 20% in backward extrusion with a reduction in cross-sectional area of 0.51 under rotation/extrusion speeds higher than 60°/mm. The influence of the friction condition, the work-hardening characteristic of the workpiece, and the reduction in cross-sectional area on the reduction in axial load was discussed using the results of finite element simulation.