In the process of die development and manufacture, stamping springback is a common problem encountered in the debugging process of automotive die test. Especially for high strength steel with yield strength over 600 Mpa, there is no perfect method to eradicate stamping springback. Junyi's engineering team is good at using AUTOFORM software to carry out CAE springback analysis, calculate stamping springback compensation, and influence impact impulse according to experience summary. The factors of pressure rebound are:
1. Performance of stamping materials
There are automobile stamping parts with different strength on automobile body. From ordinary sheet metal to high strength sheet metal, different sheet metal has different yield strength. The higher the yield strength of sheet metal, the easier the springback phenomenon will occur. For example, S500MC and DP780 are high strength steel sheets with good cold forming properties.
2. Thickness of stamping materials
In the process of metal stamping, sheet metal thickness has a great influence on bending performance. With the increase of sheet metal thickness, springback phenomenon will gradually decrease. This is because with the increase of sheet metal thickness, the material involved in plastic deformation will increase, and then the elastic recovery deformation will increase, so the springback will become smaller.
3. Shape of stamping parts
The springback of parts with different shapes varies greatly, and parts with complex shapes usually increase one-order shaping to prevent springback from forming in place, while some parts with special shapes are more prone to springback, such as U-shaped parts. In the analysis of forming process, springback compensation of stamping die must be considered. At present, European and American customers generally require that the springback compensation should be handled well in the stage of stamping die process design, and the springback should be within the product tolerance requirements.
4. Blank holder force of blank holder ring of automobile die
The blank holder force stamping process is an important technological measure. By continuously optimizing the blank holder force, the material flow direction can be adjusted and the stress distribution in the material can be improved. The increase of blank holder force can make the part drawing more fully, especially the position of side wall and R angle. If the part is fully formed, the stress difference between inside and outside will be reduced, thus the springback will be reduced.
5. Drawing rib of automobile die
Drawing ribs are widely used in today's technology. Reasonable location of drawing ribs can effectively change the direction of material flow and distribute the feed resistance on the pressing surface, thus improving the formability of materials. Setting drawing ribs on parts prone to springback will make the parts more fully formed, the stress distribution more uniform and the springback reduced.
In order to save the time of adjusting the die and reduce the cost of subsequent modification, it is necessary to use CAE simulation software to do Springback Analysis and make springback compensation and constant revision before determining the stamping process of automobile die. The commonly used software is Autoform, Dynaform and JStamp.