Prevention of seizure in inner spline backward extrusion by low-cycle oscillation using servo press

Abstract

To substitute liquid lubricants for phosphate-conversion coating in backward extrusion having severe deformation, a low-cycle oscillation backward extrusion process of a cup having inner splines using a servo press was developed. Seizure in the inside of the forged splines was prevented by low-cycle oscillation. Gaps between the punch land and the spline were caused in each release of oscillation by the difference in elastic recovery between a punch and a formed spline, and the liquid lubricant is automatically fed into a cavity under the punch through the generated gap. The effect of the oscillation on occurrence of the seizure and behaviour of the re-lubrication were investigated. In addition, the oscillated slide motion was optimised to reduce the forming time.