Effect of Tool Stiffness and Cutting Edge Condition on Quality and Stretchability of Sheared Edge of Aluminum Blanks

Stamping die design recommendations attempt to limit the production of burrs through accurate alignment of the upper and lower trimming edges. For aluminum automotive exterior panels, this translates to a clearance less than 0.1 mm. However, quality of sheared edge and its stretchability are affected by stiffness of the cutting tool against opening of the clearance between the shearing edges.

The objective of the study is to investigate the influence of stiffness of trimming or piercing dies against opening of the cutting clearance on sheared edge stretchability of aluminum blanks 6111-T4. For experimental study, one side of the sample had sheared surface obtained by the trimming process while the other side of the sample had a smooth surface achieved by metal finish. Burr heights of the sheared edge after different trimming configurations with 10% clearance were measured. Subsequently, sheared edge stretchability of the specimens was evaluated by measuring major strains of 2 mm circle grids electro-etched on the surface of the samples along the sheared edge. Comparison of burr height and sheared edge stretchability was analyzed for variable tool stiffness for trimming and piercing processes.