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Compared with ordinary stamping, precision stamping has the following characteristics:
1. Material separation form
The characteristic of material separation achieved by ordinary stamping is that when the lower edge of the stamping die is squeezed into the material to a certain depth, the material undergoes damage and micro cracks appear. The upper and lower edges have not yet contacted, and the plastic deformation of the material has been completed. At this point, the material is destroyed and divided into two parts to complete the entire punching process. Precision stamping, on the other hand, achieves material separation in the form of deformation, that is, separation is achieved only after the upper and lower cutting edges of the die come into contact. The characteristic of this separation process is that the material does not undergo damage throughout the entire stress process.
2. Section quality
The fracture of ordinary stamping is composed of four parts: collapse angle, bright zone, shear fracture zone, and burr. Shear fracture zones are formed by tearing during material failure. The surface is rough and not perpendicular to the plane of the sheet metal; The entire cross-section of precision stamping parts is full of bright bands, and there are no fracture zones formed due to material damage. So the surface is smooth and perpendicular to the plane of the sheet metal.
3. Die structure form
Precision stamping dies are similar to composite dies for ordinary stamping, except that the rigidity and machining accuracy of precision stamping dies are much higher than those of composite dies. In addition, the pressure borne by precision stamping dies is about 1.5 to 2 times greater than that of ordinary stamping dies. Therefore, the structure of precision stamping dies is relatively compact and sturdy and durable.
4. Clearance
The function of the gap between the convex and concave molds of ordinary stamping dies is mainly to establish favorable conditions for shear failure, and the value of the gap varies with the thickness of the sheet metal. The clearance between the convex and concave molds of precision stamping dies is much smaller than that of ordinary stamping dies. Its main function is to not only facilitate the establishment of a three-dimensional compressive stress state (shear force, pressing force, recoil force) to suppress the occurrence of damage, but also to facilitate the conditions for separation. At the same time, the gap should also ensure that it does not cause damage to the cutting edge. In precision stamping, the size of the gap between the convex and concave molds is closely related to the thickness of the sheet metal.
5. Blade edges of convex and concave molds
The edges of ordinary convex and concave molds should be as sharp as possible, in order to form obvious uneven deformation and stress concentration, and promote the formation of conditions for damage to the plate. The convex and concave die edges of precision stamping may not necessarily be made very sharp, but sometimes they must be made in the form of rounded corners and arcs, in order to create a three-dimensional compressive stress state and suppress the occurrence of sheet metal damage.
6. Burrs
The formation of burrs in ordinary stamping occurs before the plastic deformation of the material is almost completed and shear cracking begins. Later, with the movement of the punch, the burrs are compressed and deformed by the rough section formed during the destruction of the sheet, causing the burrs to elongate. The size of burrs is not directly proportional to the gap. The burrs of precision stamping are formed at the end of sheet separation, and after the burrs are formed, they no longer deform and basically maintain their original size and shape.
7. Ultimate dimensions of the workpiece
Ordinary stamping can generally only punch workpieces with a minimum width and aperture equivalent to the material thickness, while precision stamping can punch workpieces with a width less than 0.5~0.7mm of the material thickness, and can also be used for stamping and forming processes.
8. Requirements for raw materials
Ordinary stamping has no special requirements for raw materials, while precision stamping requires good plasticity of raw materials. For materials with low plasticity, annealing is required before stamping to improve their plasticity.
9. Using equipment
Precision stamping requires more complex equipment than ordinary stamping, typically using three action and specialized precision stamping presses. But if specialized precision molds are used, precision stamping work can also be carried out on ordinary presses.
10. Cost
For the same stamping part with high precision requirements, using precision stamping method greatly reduces the cost compared to using ordinary stamping method. Precision stamping is a relatively economical machining process.
