At present, the common process measures to solve the springback of sheet metal stamping are as follows:
1. Correction bending
The correction bending force will concentrate the punching force in the bending deformation zone, forcing the inner metal to be squeezed. After correction, the inner and outer layers are stretched. After unloading, the rebound trends of the two extrusion zones offset each other to reduce the rebound.
2. Heat treatment
Annealing before bending to reduce its hardness and yield stress can reduce the rebound, and also reduce the bending force. Harden again after bending.
3. Excessive bending
During bending production, due to elastic recovery, the deformation angle and radius of the sheet metal will increase. The sheet metal deformation degree can be used to reduce the rebound by exceeding the theoretical deformation degree.
4. Hot bending
By using heating bending and selecting the appropriate temperature, the material has enough time to soften, which can reduce the amount of rebound.
5. Stretch bending
This method is to apply tangential tension while bending the sheet metal, change the stress state and distribution inside the sheet metal, and make the entire section within the range of plastic tensile deformation. After unloading, the rebound trends of the inner and outer layers offset each other, reducing the rebound.
6. Local compression
The local compression process is to increase the length of the outer sheet by thinning the thickness of the outer sheet, so that the rebound tendency of the inner and outer layers offset each other.
7. Multiple bending
Bending is divided into multiple times to eliminate springback.
8. Inner corner blunting
Compress from the inside of the bending part to eliminate springback. When the plate is U-shaped, this method is more effective because of the symmetrical bending on both sides.
9. Change the overall drawing to partial bending
Bending a part of the part and then drawing it to reduce springback. This method is effective for products with simple two-dimensional shapes.
10. Control residual stress
During drawing, a local convex shape is added to the surface of the tool, and the added shape is eliminated in the subsequent process to change the residual stress balance in the material to eliminate springback.
11. Negative springback
When processing the tool surface, try to make the sheet metal produce negative springback. After the upper die returns, the workpiece reaches the required shape through springback.
12. Electromagnetic method
Using electromagnetic pulses to impact the surface of the material can correct shape and size errors caused by rebound.
