Working of sheet metal

Abstract

The apparatus includes a main anvil tool 10 for constraint of a first surface 3 of a sheet metal workpiece 1. A main forming tool 40 is for constraining two adjacent basal regions (50, 60, Figure 2B) of the workpiece between the anvil tool and the forming tool such that the regions are fixed relative to the anvil tool. An auxiliary forming tool 30 is for contact with a second surface 5 of the workpiece. An auxiliary anvil tool 20 is for contact with the first surface. The auxiliary forming tool is directed along an axis to contact the workpiece to bend sidewall portions 51, 61, with respect to the basal regions, to form a first fold region 55, until the first surface contacts the auxiliary anvil tool. Concurrently, progressively sliding first fold contact regions of the auxiliary forming and anvil tools along the first fold region to conduct shear material transfer. The region has at least one ridge line and crease line, each extending from a vertex of the region to the workpiece edge. Along a majority of their length from the vertex to the edge, one or both of the ridge and crease lines have non-zero Gaussian curvature. [Figure 3A]