The effect of the die radius profile accuracy on wear in sheet metal stamping

This paper investigates the influence of the die corner radius shape on wear behavior during sheet metal stamping. In particular, small and localized changes from an ideal circular die profile shape were examined and the effect on tool life determined. A novel technique to test and characterize the die profile shape and wear behavior, based on a semi-industrial channel forming process, is presented. It will be shown experimentally that small changes in die radius profile shape (of less than 15 μm) can result in significantly reduced tool life. In all cases examined, the small variations in shape were the result of inherent variations associated with the machining, grinding and polishing processes typically used to manufacture stamping dies and die corner inserts. Numerical simulation shows that these small shape ‘defects’ at the die corner radius can result in a significant increase in local contact pressures, explaining the large adverse changes in tool life. These results are of direct importance to stamping engineers and tool designers and indicate that careful control over die manufacture and maintenance procedures may result in significant improvements in tool life.

► We used novel techniques to test and characterize die profile shape and wear behavior.
► Strong relationship between tool life and small die profile shape changes.
► Small shape ‘defects’ (<15 μm change from ideal) result in ∼90% drop in tool life.
► These small shape defects more than double steady contact pressures at die radius.