Punch plays a very important role in the die. Its design shape, dimensional accuracy and material hardness directly affect the blanking quality, service life and the accuracy of stamping parts. In the actual production and processing, due to the residual stress deformation inside the workpiece blank and the thermal stress deformation caused by discharge, the threading hole should be machined first and closed cutting should be carried out to avoid the deformation caused by open cutting as far as possible. If the closed form cutting can not be carried out due to the size of the workpiece blank, the cutting route (or cutting direction) should be selected when programming the square blank.
The cutting route should be conducive to ensure that the workpiece is always kept in the same coordinate system with the fixture (clamping support frame) in the process of processing, so as to avoid the influence of stress and deformation. The fixture is fixed at the left end and cut from the left side of the gourd punch in a counter clockwise direction. The whole blank is divided into left and right parts according to the cutting route. Because the material connecting the left and right sides of the blank is smaller and smaller, the right side of the blank is gradually separated from the fixture, which can not resist the internal residual stress and the workpiece is deformed. If the workpiece is cut clockwise, it will stay on the left side of the blank, close to the clamping position. Most of the cutting process will keep the workpiece and fixture in the same coordinate system, with good rigidity and avoiding stress deformation. In general, the reasonable cutting route should arrange the cutting section separating the workpiece from the clamping part at the end of the total cutting procedure, that is, the pause point (support part) should be left near the clamping end of the blank.
