The mold used for stretching is called a stretching die, which is a specialized tool for batch processing materials (metal or non-metal) into the required stamping parts. If the types of drawing dies are distinguished by combination, they can be divided into single process drawing dies, composite dies, and progressive drawing dies. Distinguished by stamping equipment, it can also be divided into drawing dies for single action presses, drawing dies for double action presses, and drawing dies for three action presses. The main conditions for distinguishing them are the differences in edge holding devices (elastic edge holding and rigid edge holding). The drawing die can also be divided into the first drawing die and the subsequent drawing dies for each process, with the main difference being the structure and positioning method of the blank holder.
Thinning stretching die, thinning stretching and general stretching are greatly different. The characteristic of thinning stretching is that the diameter change of the stretched part is relatively small, and the thickness of the bottom of the workpiece does not change. However, the side wall thickness of the workpiece becomes thinner during the deep drawing process, and the height of the workpiece increases accordingly. Thinning drawing die: When the convex die is punched down, it passes through the concave die (two pieces) to perform secondary thinning and deep drawing on the blank. When the convex die rises, the unloading ring assembly blocks the deep drawn part from the convex die.
There is also a reverse drawing die. The working principle of a square drawing die is to flip the inner wall of the workpiece outward, and the contact surface between the workpiece and the concave die is large. Due to the high dynamic resistance of the workpiece material, there is no need for a press ring. Due to the fact that the outer diameter of the concave mold is smaller than the inner diameter of the process part, the tensile coefficient of all reverse stretching cannot be too large. If it is too large, the wall thickness of the concave mold is too thin and the strength is insufficient.
