What is the reason for the wrinkling of stamping and drawing die products?
- Factors and solutions that affect the wrinkling of stamping parts
1. The effect of stretching depth
The distribution of flow resistance along the die opening is directly related to the draw depth. On the concave and convex position, excessive stretching depth will lead to uneven distribution of deformation resistance and the formation of wrinkles. This should be avoided as much as possible.
2. Adjust the blank holder force
If wrinkles are evenly generated around the workpiece, it is judged that the holding force is insufficient, and the wrinkles can be eliminated by gradually increasing the blanking force. When stretching conical and hemispherical parts, most of the material is in air at the beginning of the stretching. Since the side wall is prone to wrinkling, it is not only necessary to increase the blank holder force, but also to increase the radial tensile stress in the plate by adding pick-up ribs and eliminate wrinkles.
3. Influence of die fillet radius
The radius of the die fillet is too large, and the blank flows into the die and passes through the die fillet, resulting in bending deformation, and the bending resistance is small. The lower the bending resistance, the easier it is to cause wrinkling. The smaller the bending deformation of the die radius, the greater the bending resistance and the smaller the possibility of wrinkling, but it is easy to cause parts to crack and pull.
Through the accumulation of practical experience in mass production, it is proved that the main reasons for the wrinkling of stamping parts are the accumulation of materials during the stretching process and the excessive speed of some materials. When formulating a practical solution, the above aspects should be considered to adjust the corresponding mold mechanism to achieve good results.
2. Measures and methods to prevent wrinkling of stamping parts
The method to prevent wrinkling is to ensure that the die can press the material during the drawing process of the metal stamping part to ensure the flow speed of the sheet. When the stamping part is stretched, the material flows too fast, which will cause wrinkles; on the other hand, the material flows too slowly, which will cause stamping cracks.
1. Use a reasonable pressing device
When the pressing device is used, the pressing device presses the deformed part of the blank, and aligns the pressing force to prevent the flange part from arching and causing wrinkles. The size of the pressing force should be appropriate. The pressing device is divided into two types: elastic pressing and rigid pressing. The elastic device is suitable for shallow drawing, and the rigid device is suitable for deep drawing.
2. Reasonable use of drawbeads
Setting drawbeads on the binder surface is an effective method to adjust and control the deformation resistance. Drawbeads can well adjust the flow of materials, so that the material flow resistance of each part during the drawing process is uniform, so that the amount of material flowing into the cavity is suitable for the needs of the workpiece, and the phenomenon of wrinkling and cracking is prevented. For curved stretched parts with complex shapes, especially those with smaller flanges, drawbeads should be set to increase the radial tensile stress of stretching to control wrinkling;
The location of the drawbead is where the radial tensile stress is smaller, that is, the location where the sheet is easy to flow. For parts with small flanges, in order to set the draw bead, some materials (process supplementary materials) can be added appropriately, and this part is removed when trimming. For drawing parts with large difference in drawing depth, draw beads should be set in the part with a small amount of feed, so as to prevent excessive material from being pulled into the mold cavity to prevent wrinkling.
3. Analysis of the causes of wrinkling of tensile parts
There are many reasons for wrinkling during stretching, the main reasons are as follows:
1. The drawing depth of the stamping part is too deep, which causes the sheet material to flow too fast during the feeding process and form wrinkles.
2. During the stretching process of the stamping part, the R angle of the die is too large, so that the punch cannot press the material during the stretching process, causing the sheet to flow too fast to form wrinkles.
3. The pressing of the stamping parts is unreasonable, the pressing ribs are too small, and the position is incorrect, which cannot effectively prevent the sheet material from flowing too fast and forming wrinkles.