THE EFFECT OF PUNCH GEOMETRY ON PUNCHING PROCESS IN TITANIUM SHEET

Abstract

Reducing punch force, increasing the sheared surface, and improving the work hardening have been real challenges in developing a punching process, and the right selection of punch geometry can resolve these challenges. Selecting the appropriate geometry, however, has been difficult to do since the effect of punch geometry on the punching process is rarely studied, and therefore, this study aims to investigate the effect of punch force, sheared surface, and work hardening by using commercially pure titanium sheets. The punching process under the study employed three different punch geometries, namely flat (FLAT), single shear angle (SSA) and double shear angle (DSA) with a shear angle of 17°, while the Punch velocity used was 35mm/s and 70 mm/s. The results show that the punching process using SSA and DSA punch geometry with the punch velocity of 35 mm/s reduces the punch force by 18% and 13% consecutively compared to that of FLAT with the same velocity. However, the sheared surface quality seems to decline as the rollover height increases by about 48% and 32%. Moreover, the burnish height decreases by 34% and 7% and the resulted work hardening improves by 4.7% and 2.3% respectively. The study concludes that SSA and DSA punch geometry can be best used to reduce punch force and increase work hardening, but apparently fail in increasing the sheared surface quality.