Springback factors and control methods of metal stamping parts

From the experience of developing and manufacturing all kinds of metal stamping dies, it is known that drawing dies are difficult to handle, because the material will flow, and the problem of stamping springback is sometimes a headache. At present, there is no accurate and reliable springback calculation formula, and everyone usually compensates for different materials and different R angles based on experience. So what factors affect the springback of metal stamping parts?

1. Mechanical properties of stamping materials

There are metal stamping parts with different strengths on automobiles. From ordinary plates to Gao Qiangban, different plates have different yield strengths. The higher the yield strength of plates, the more likely it is to rebound, especially DP series dual-phase high-strength steel.

2. Thickness of stamping material

In the forming process, the thickness of sheet metal has a great influence on the bending performance. With the increase of sheet metal thickness, the springback phenomenon will gradually decrease, because with the increase of sheet metal thickness, the materials participating in plastic deformation increase, and then the elastic recovery deformation also increases, so the springback becomes smaller.

With the continuous improvement of the material strength level of thick plate parts, the problem of dimensional accuracy of parts caused by springback becomes more and more serious. Mold design and later process debugging require an understanding of the nature and size of springback of parts in order to take corresponding countermeasures and remedies.

3. Shape and complexity of stamping parts

The springback of parts with different shapes varies greatly. Parts with complex shapes generally add a sequence of shaping to prevent springback from occurring when the forming is not in place, while some parts with special shapes are more prone to springback, such as U-shaped parts. In the analysis and forming process, springback compensation must be considered.

4. Blank-holding force of stripper of die parts

Blank holder force stamping process of die stripper is an important technological measure. By continuously optimizing blank holder force, the material flow direction can be adjusted and the stress distribution inside the material can be improved. The increase of blank holder force can make the drawing of parts more complete, especially the position of side wall and R angle. If the forming is sufficient, the internal and external stress difference will be reduced, thus reducing the springback.

5. Die drawbead

Die drawbead is widely used in today's technology. Reasonable setting of drawing position can effectively change the direction of material flow and effectively distribute the feeding resistance on the blank pressing surface, thus improving the formability of materials. Setting drawbead on parts prone to springback will make the parts more fully formed and the stress distribution more uniform, thus reducing springback.

How to control the rebound of metal stamping parts?

The best time to reduce or eliminate stamping springback is in the stage of product design and die development. With the help of pre-CAE springback analysis, the springback is accurately predicted, the product design and process are optimized, and the springback is reduced by product shape, process and compensation. In the debugging stage of hardware mold, we must try the mold in strict accordance with the guidance of process analysis. Compared with ordinary SE analysis, the workload of springback analysis and correction increases by 30% ~ 50%, but it can greatly shorten the mold debugging period.

Springback is closely related to the drawing process. Under different drawing conditions (tonnage, stroke and feed rate, etc.), although the stamping parts have no forming problems, the springback after trimming will be more obvious. The springback analysis uses the same software as the drawing forming analysis, but the key is how to set the analysis parameters and evaluate the springback results effectively.