Every stamping worker plaguing the wrinkle problem

Factors affecting the wrinkling of stamping parts and solutions

1. Drawing depth influence

There is a direct relationship between the material flow resistance along the die orifice distribution at the depth of the drawing. In the position of the concave and convex curves, excessive Drawing depth can cause uneven distribution of deformation resistance, and wrinkles should be avoided.

2.  Adjust the size of the blanking force

When the wrinkles are uniformly generated around the workpiece, it should be judged that the pressing force is insufficient, and the pressing force is gradually increased to eliminate the wrinkles. When the cone and hemispherical members are drawn, most of the material is in a suspended state at the beginning of the drawing. It is easy to result sidewall wrinkles. so except increasing the blanking force at the deep drawing pieces edges, it should also increase the radial tensile stress in the panel to eliminate wrinkles.

Stamping part tooling example

3. The influence of Female block radius of the stamping part

The radius of the female stamping die is too large, and the flow of the blank into the die through the die radius is the bending resistance that causes the bending deformation to be smaller. The smaller the bending resistance, the more likely to cause wrinkles. The greater the bending resistance of the concave die with small bending deformation, the less likely to wrinkle, but it is easy to cause cracking and pulling scree of the workpiece. Through a large number of production practice and accumulation of experience, the main reason for the wrinkling of stamping parts is caused by the accumulation of materials during the drawing process and the excessive speed of local material movement.

About the solution, we should consider the above aspects and adjust the corresponding mechanism of the mold, which will achieve good results.

Measures to prevent wrinkling of stamping parts is ensure that the metal stamping parts can press the material during the drawing process with reasonable sheet flow speed. When the stamping part is stretched too fast, the sheet material may be wrinkled; on the other hand, if the sheet material flows too slowly, the stamping part may be cracked.

(1) Using a reasonable press device

When the pressing device is used, the pressing device presses the deformed portion of the blank tightly and acts on the pressing force to prevent the flange portion from arching and causing wrinkles. The amount of pressing force should be appropriate. The pressing device is divided into two types: elastic pressing material and rigid pressing material. The elastic device is suitable for shallow drawing and the rigid device is suitable for deep drawing.

(2) Reasonable use of draw beads

The design of the draw bead on the pressing surface is an effective method for adjusting the deformation resistance. The draw bead can adjust the flow of the material well, so that the material flow resistance of each part during the drawing process is uniform, and the amount of the material flowing into the cavity is suitable for the needs of the workpiece, preventing more wrinkles and less cracking. The phenomenon. For curved joints with complex shapes, especially those with smaller flanges, draw beads should be provided to to control wrinkling; the position of the draw beads is radially pulled. On the part where the stress is small, that is, the part where the sheet is easy to flow. For parts with small flanges, in order to set the draw beads, some materials (process supplements) can be added as appropriate, and this part is removed when trimming. For large depth of deep drawing part, the draw beads should be placed at a location where there is less feed, so that too much material can be organized in the cavity to prevent wrinkles.

4. Analysis of the causes of wrinkles in drawing parts

There are many reasons for the wrinkles of the tensile members during the drawing process. 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 to form wrinkles.

(2) The R angle of the die is too large during the drawing process, 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 material of the stamping part is unreasonable, the pressing material rib is too small and the position is not correct, which can’t effectively prevent the sheet material from flowing too fast and forming wrinkles.

Deep drawing beads example

(4) The pressure of the ejector pin is too small, so that the stamping parts are not formed completely and wrinkles are formed.

(5) The mold positioning design is unreasonable, which leads to the inability to press the material during the drawing process of the stamping part or the side of the pressing material is too small, which makes it impossible to press the material during the stretching process and cause wrinkles.

(6) The excessive gap between the convex and concave molds makes it impossible to press the material during the stretching process, causing wrinkles. The above is a common cause of wrinkling during the stretching process of metal stamping parts, and specific analysis is needed in specific problems. Find the specific reason based on the specific conditions of the stamping.

Soucing from: https://sipxmach.com/every-stamping-worker-plaguing-the-wrinkle-problem/