What is the reason for the wrinkles of the drawn parts? How should it be eliminated and resolved?

Wrinkling of deep-drawn parts (as shown in the figure below) is a quality problem often encountered in the production of metal stamping. It is caused by the fact that the flange part of the material loses stability during the deep drawing process or the excess material cannot diffuse outward due to the large flow of the material. The following measures can be taken to prevent and correct the wrinkles of the drawn parts: 1) Adjust the blank holder force During the deep drawing process, the blank holder force cannot be too large or too small, and it must be uniform everywhere. Too small a blank holder force is easy to cause wrinkles in the drawn part, and a too large blank holder force is easy to break the drawn part, the blank holder force is uneven, and the drawing part may wrinkle on one side. Therefore, attention should be paid to adjusting the blank holder force appropriately during deep drawing. 2) The thickness of the measured material is incorrect or the negative difference is too large, the drawn part is easy to wrinkle, and the uneven thickness of the material will cause wrinkles on one side of the drawn part. The material with uneven thickness can be rolled once before drawing. 3) The gap between the convex and concave molds is too large, the straightening effect is reduced, and the material is easy to wrinkle. But the gap is uneven, and the drawn part will wrinkle on one side. The gap between the convex and concave molds can be properly trimmed. 4) Die fillet The die fillet is too large, which reduces the contact area between the blank holder and the material and causes the drawing part to wrinkle. The die fillet can be properly trimmed. 5) For some deep drawn parts with complex curved surfaces, especially small flange parts, drawing ribs can be set on the mold to increase the flow resistance of the material to prevent the drawn parts from wrinkling, as shown in the figure below. 6) For spherical parts, conical parts and parabolic parts, the reverse drawing method is used to increase the deformation resistance of the material to prevent the drawn parts from wrinkling, as shown in the figure below. 7) Too much lubricant is applied, which may cause excessive local feeding and cause wrinkles. Lubrication should be carried out correctly. 8) The pressing surface, the die surface or the drawing bead is severely worn, which makes it difficult to control the feeding speed of the uneven material and cause wrinkles. The pressing surface, die surface and drawing bead should be trimmed. 9) For stainless steel and other plates with severe work hardening in deep drawing where the blank holder force is 1 to 2 times the drawing force, if the punch has insufficient rigidity, no matter how to increase the blank holder force, the wrinkles of the drawn parts cannot be eliminated. At this time, a large-tonnage punch can be used instead, and a closed punch or hydraulic press can be used for deep drawing. Previous post: What does stamping reverse drawing mean? What are the characteristics and uses of reverse drawing?