When punching a workpiece is placed on the lower tool, the die [1]. The upper tool, the punch [2], is pressed against the workpiece with an applied punch force. Depending on the design of the workpiece, one or more subsequent strokes are done.
When punching out a hole the material is exposed to shear between the punch and the die. During the punching process the material is displaced and then loosen completely by material failure. This gives both stamped detail and bore the typical cut surface caused by punching consisting of a smooth surface where the material has slid and a rougher surface where the deformation occurred.
Precision stamping differs from ordinary punching by a clamping ring [3], which presses down and locks the plate around the contour which minimizes the fracture surface. This causes higher tolerances while minimizing deformation around the hole. Clamping ring also ensures that the sheet detaches from the punch if it’s wedged in the plate after the stroke.
There are a variety of punching tools that can do everything from cutting straight lines and creating threaded holes to engrave and carry out bending operations.
In cases where the tools are designed to carry out compression forming, the sheet is deformed by plastic deformation.
Usually the workpiece is moved while the tool maintains its position and can rotate.
