Numerical and Experimental Investigations to Increase Cutting Surface Quality by an Optimized Punch Design

Abstract

Punching is one of the most commonly used production processes in sheet metal working industry. Here, major criterion for the quality of cutting surfaces is a high clean cut proportion. However, the disadvantage of conventional punching processes is that they can only produce clean cut proportions up to 20–50% of the sheet thickness. Until today, more complex processes such as fine blanking are therefore required for a higher cutting surface quality. The content of this paper is a numerical and experimental investigation for a new tool design called “concave punch nose design”. The idea of the concave punch nose design is to optimize the cutting edge geometry of conventional punches in order to enlarge clean-cut proportion along the cutting surface despite a process sequence similar to conventional shear cutting. The numerical and experimental investigations presented in this contribution show, that the concave punch nose design increases compressive stresses in the shear-affected zone and therefore significantly raises the cutting surface quality. Compared to conventional punching, concave punch nose design increases clean cut proportions by more than 100%.