Dependencies of the die-roll height during fine blanking of case hardening steel 16MnCr5 without V-ring using a nesting strategy

Abstract

For economic reasons, fine blanking of asymmetric parts is performed with shifted and rotated part nesting. It was observed that both the part position and the part orientation on the sheet metal strip affect the die-roll height. Therefore, the influence of the bridge width between the produced cutting line and the strip edge or existing sheared edges was studied in this work. Additionally, the effects of the stroke number, the convexity of the radii and the sheet metal anisotropy were considered. The parts were manufactured in a production series of 40,000 parts with a fine blanking tool ejecting four parts simultaneously. From each nest, 20 parts were separated at four equidistant steps. The die-roll height was determined in three regions with different convexity radii of parts from varying nests. A normal distribution was found for the die-roll height, categorized by convexity radius and position of the nest. The die-roll height was found to be promoted by convexity radius, small bridge width, and in transverse blank direction. The number of strokes had a minor impact. Interaction effects occur particularly at small convexity radii and small bridge widths. As a conclusion, the nesting must be considered in order to reduce the die-roll height. Small bridge widths, small convexity radii, and the orientation in transverse blank direction have a negative impact, whereas the stroke number has a marginal influence. The understanding of the correlation between die-roll formation and nesting helps to reduce waste in mass manufacturing.