Effect of Trimming Process Parameters on Sheared Edge Geometry and Stretch Limit: An Experimental Investigation

The stretchability and flangeability of sheared sheet metal in stamping are directly influenced by the trimmed edge quality. In this work, the effect of the trimming parameters on the edge quality was investigated using experimental and statistical approaches. The material of study was a 6xxx-series aluminum sheet. A digital 3D optical microscope was used to assess the quality of the sheared edge geometry by measuring several distinct trimmed edge geometrical features, namely rollover, burnish, fracture, and burr. The evolution of the sheared edge geometry was studied by changing four trimming parameters, namely clearance, offal support, lower tool sharpness, and upper tool sharpness. The sheared edge’s ability to stretch was assessed by measuring both the total elongation and the local strain of trimmed half dog-bone specimens tested under uniaxial tensile loading conditions. A generalized linear model regression was used to investigate the relationship between the edge stretch, edge geometry, and trimming process parameters. The burr size was found to be the most significant factor for predicting elongation, while clearance between the upper tool and the lower tool was found to be the most significant controllable regression variable. Furthermore, the use of high support was reported to decrease the sensitivity of the trimmed edge quality to the upper and lower tool sharpness.