The Causes and Control Methods of Wrinkling in Stamping Forming

The Causes and Control Methods of Wrinkling in Stamping Forming

1. Factors affecting wrinkling of stamped parts and their solutions

(1) Effect of deep drawing depth

The distribution of material flow resistance along the concave die is directly related to the deep drawing depth. Excessive deep drawing depth on concave and convex curve positions can cause uneven distribution of deformation resistance and wrinkling, which should be avoided as much as possible.

(2) Adjusting the magnitude of the edge pressing force

When wrinkles are evenly formed around the workpiece, it should be judged as insufficient pressing force. Gradually increasing the pressing force can eliminate wrinkles. When deep drawing conical and hemispherical parts, most of the material is in a suspended state at the beginning of the deep drawing process. It is easy to cause wrinkles on the side walls, so in addition to increasing the edge pressing force, it is also necessary to increase the tensile stress on the inner diameter of the plate by adding picking and deep drawing bars to eliminate wrinkles.

(3) The radius influence of concave die fillet

The fillet radius of the concave mold is too large, and the flow of the blank into the concave mold through the concave mold fillet results in a smaller Bending resistance that causes Bending deformation. The smaller the bending resistance, the more likely it is to cause wrinkling. The smaller the radius of the concave mold, the greater the bending resistance of the bending deformation, and the less likely it is to wrinkle, but it is prone to cracking and roughening of the workpiece.

Through extensive production experience, it has been proven that the main cause of wrinkling in stamped parts is the accumulation of materials during the deep drawing process and the excessive speed of local material movement. When formulating practical solutions, the corresponding mechanism of the mold should be adjusted from the above aspects to achieve good results.

2. Measures and methods to prevent wrinkling of stamped parts

The method to prevent wrinkling is to ensure that the mold can hold the material during the deep drawing process of the stamped part, and to ensure a reasonable flow rate of the sheet metal. If the sheet metal flows too fast during deep drawing, it can cause wrinkling; On the other hand, slow flow of sheet metal can cause cracking of stamped parts.

(1) Using a reasonable pressing device

When using a pressing device, the pressing device tightly presses the deformed part of the blank and exerts a pressing force on it to prevent the flange from arching and causing wrinkles. The size of the pressing force should be appropriate. The pressing device is divided into two categories: elastic pressing and rigid pressing. Elastic devices are suitable for shallow drawing, while rigid devices are suitable for deep drawing.

(2) Reasonable use of deep drawing bars

Setting deep drawing ribs on the pressing surface is an effective and practical method for adjusting and controlling deformation resistance. deep drawing ribs can effectively regulate the flow of materials, making the flow resistance of materials in various parts uniform during the deep drawing process, and ensuring that the amount of material flowing into the mold cavity is suitable for the needs of the workpiece, preventing the phenomenon of wrinkling when there is more and cracking when there is less. For complex curved deep drawing parts, especially those with smaller flanges, deep drawing ribs should be set up to increase the radial tensile stress during deep drawing and control wrinkling; The setting position of the deep drawing rib is in the area where the radial tensile stress is small, that is, the area where the sheet metal is easy to flow. For parts with smaller flanges, in order to set up deep drawing ribs, some materials (process supplementary materials) can be added appropriately, and this part can be removed during edge trimming. For drawn parts with significant differences in deep drawing depth, the deep drawing ribs should be set in areas with less feed, so as to prevent excessive material from being pulled into the cavity of the die and prevent wrinkling.

3. Analysis of the causes of wrinkling in stretched parts

There are many reasons for wrinkling of stretched parts during the deep drawing process, and the main reasons are as follows:

(1) The deep drawing depth of stamped parts is too deep, causing the sheet metal to flow too quickly during the feeding process, resulting in wrinkling.

(2) During the deep drawing process of stamped parts, the R angle of the concave die is too large, causing the convex die to be unable to press the material, resulting in the rapid flow of the sheet metal and wrinkling.

(3) The pressing ribs of the stamped parts are unreasonable, too small and positioned incorrectly, which cannot effectively prevent the rapid flow of the sheet metal and form wrinkles.

(4) The pressure on the top rod is too small, resulting in incomplete forming of the stamped part and wrinkling.

(5) The unreasonable positioning design of the mold results in the inability to press the material during the deep drawing process of the stamped part or the small pressing edge, which leads to the inability to press the material during the deep drawing process and causes wrinkling.

(6) The large gap between the convex and concave molds results in the inability to press the material during the deep drawing process, causing wrinkling.

The above are common causes of wrinkling during the deep drawing process of Stamping parts, and specific analysis is needed in specific problems. Find the specific cause based on the specific situation of the stamped parts.