The difference between the dimensions of the convex and concave parts is called the gap. Blanking die gap is the double gap. The gap value is represented by the letter Z. Gap is important, reflected in the following aspects:
1) the influence of blanking clearance on the quality of blanking parts
(1) clearance section quality effect of die gap is reasonable and the convex die and the concave die crack (crack) in stamping process meet and overlap, this section collapse angle is small, wide proportion of smooth, burr smaller, easy to remove. The section quality is better; if the gap is too large, the crack punch edge reasonable gap inward shift for a certain distance, the material not overlapping part of the upper and lower crack will be affected by the tension caused tear, the sinking angle increases, wool face widened, smooth cut, burr fat and long, it is difficult to remove section, poor quality; the gap is too small, the crack punch and die edge reasonable clearance outward shift for a certain distance on the middle part of the crack material, with the punching shear will be two times, so that the two optical surface, section and, due to the decrease of gap the material squeezed component increases, and reduce the angle of hair surface collapse, burr less, the best quality section. Therefore, it is a key to determine the correct blanking gap for the general blanking.
(2) the impact of the blanking clearance on the dimension accuracy of the material will produce a variety of deformation, so as to produce a rebound, so that the size of the workpiece is different from the die and the punch edge size. As a result, the size of the workpiece is changed, some of them are decreased. The general rule is that the hours gap, falling materials size is larger than the die size, out of the aperture is less than the convex mold size; large gap, size of materials and parts of concave die size is less than that out of the aperture is larger than that of the convex mold size.
2) the influence of the blanking gap is not great. But the gap is not big, but the gap has a great influence on the unloading force and pushing force. When the gap is larger, the friction resistance is small, and it is easy to unload material from the top of the convex mold and push the material from the die.
3) the impact of the blanking clearance on the life of the die is due to the punch, the material and the die between the punch and the die. And the size of the gap directly affects the size of the friction. The smaller the gap, the more serious the friction caused by friction, the shorter the life of the die, and the larger the gap, can make the wear and tear caused by the friction, thus improving the service life of the die.