The Application of hard film coating for extension tool life on inclined punch in the trimming process

Abstract

The objective of this research is to increase the tool life of trimming process by surface coating technology. The procedure of this research consists of two sections. In the first section, the friction coefficient was investigated with the ball on disk technique by using a tribometer. Steel ball was produced from cold work tool steel grade SKD11 (JIS) hardened to 60±2 HRC. Two types of surface coating, namely AlCrN and TiAlN, were conducted by PVD technique. Disk material used in this experiment was made by stainless steel JIS; SUS 304 of 2 mm thickness. For the second section, the wear tests of trimming die were performed by using flat punch and inclined punch 45 degrees without surface coating as well as the inclined punch 45 degrees coated with AlCrN and TiAlN (PVD). Workpiece material used for the wear test was stainless steel JIS; SUS 304 of 2 mm thickness. Additionally, the finite element analysis was carried out for explanation the deformation of the workpiece during trimming operation. Although the friction coefficient of the surface coating was higher than non-coating, it could be extended the tool life ostensibly. As the result of FEM, the inclined punch 45 degrees could be generated the long sheared surface more than the flat punch. This is due to the internal stress of workpiece that did not connect from the punch to the die, so the crack propagation would be delayed. The inclined punch 45 degrees coated TiAlN has a highly durable which can be used up to 5,000 strokes.