The process of punching the die

There are three stages in the stamping die deformation:

1. Elastic deformation stage (the material stress inside the deformation zone is less than the yield stress);

2. Plastic deformation stage (the material stress inside the deformation zone is greater than the yield stress);

3. The fracture separation stage (the material stress inside the deformation zone is greater than the strength limit).

Blanking is a general term for the separation process, but generally refers to blanking and punching. If the purpose of the punching is to make a workpiece of a certain shape, it is called blanking; if the purpose is to obtain the inner hole, it is called punching. Here mainly introduces the blanking process of blanking. When punching, the punch and die of the die form a pair of sharp edges, and the sheet is placed on the die, and the punch gradually descends to force the sheet to deform until it is separated.

    (1) Elastic deformation stage. The elastic deformation stage is shown in Figure 3-15. The punch presses down the sheet and begins to force the sheet to elastically compress and bend and slightly squeeze into the die cavity. Finally, as the punch continues to press in, the internal stress of the material reaches the elastic limit.

    (2) Plastic deformation stage. The plastic deformation stage is shown in Figure 3-16. The punch continues to drop and the pressure increases. When the stress reaches the yield limit, the material undergoes tensile and bending plastic deformation, and stress concentration occurs at the edge of the convex and concave die. This stage continues until the material near the edge of the relief die is slightly cracked.

    (3) Shear fracture stage. The shear fracture phase is shown in Figure 3-17. When the punch continues to descend. The stress reaches the shear strength of the sheet. The micro-cracks near the die edge continue to expand into the interior of the sheet. When the die gap is reasonable, the upper and lower cracks are turned on, and the material is broken and separated. Thereafter, if the punch continues to descend, the separated material is pushed out of the die.

    There are five places where the mold and the billet come into contact during the blanking process: between the convex and concave end faces and the blank; between the convex and concave side walls and the blank; after the blank breaks, the residual material is between the workpiece and the workpiece; Between the hole and the sidewall of the punch; between the sidewall of the workpiece and the wall of the die.