PRESSBRAKE BENDING IN THE PUNCH-SHEET CONTACT REGION - PART 2: GAP FORMATION AND THE DIRECTION OF SHEET MOTION.

In Part 1 of this paper, simple models of nonuniformities in pressbrake bending in the punch-sheet contact region were presented. An extreme manifestation of these nonuniformities is the appearance of a gap between the punch and the sheet. The models from Part 1 are used in Part 2 to predict the possible formation of this gap as a function of the geometry and the frictional conditions. To determine the direction of the frictional force at the die, methods to determine the direction of sheet motion on the die are presented. Elastic and rigid-plastic material models of the sheet are considered, and are shown to produce remarkably similar results.