| The punch is machined on a CNC Machining Center, with the radius of the peaks exactly matching the size and shape of the convex shapes. In the valley portion of the punch, a projection is machined in each valley, to provide enough area for the sheet metal to gather the excess material. The Urethane bottom Die is molded with the same corrugated sheet as the sheet metal being bent. This is molded in a welded steel box, strong enough to contain the Urethane , and re-direct the forming forces up-wards, to force the sheet metal tightly against the machined punch, stretching the sheet metal around the convex parts of the punch and collapsing the sheet metal uniformly in the concave parts of the punch. With the urethane in the bottom, there is no marking on the sheet metal. |