Reasons for the wavy patterns on the surface of stamped automobile covers

Reasons for the wavy patterns on the surface of stamped automobile covers

Automobile covers belong to stamped parts, and the quality of automobile covers directly affects the quality of the car body. Stamped parts often have some surface quality problems during the stamping process. Automobile covers are prone to some wrinkles (also called ripples or waves) during the stamping and drawing process.

Wrinkling is one of the serious problems in the stamping and drawing process. The so-called wrinkling refers to the uneven wrinkles along the tangential direction of the edge of the blank during the drawing process.

Why do stamped parts wrinkle during the drawing process? Simply put, this is caused by the instability of the flange part due to excessive tangential stress. If the wrinkles are very small, they will be flattened when passing through the gap between the convex and concave dies. If the wrinkles are serious, the deep-drawn parts will break because the resistance of the wrinkles when passing through the gap between the convex and concave dies is too large. Even if the wrinkles pass through the gap between the convex and concave dies, the stamped parts will be scrapped because the wrinkles cannot be flattened.

The waves on automobile covers are very slight wrinkles, which are mainly produced near the edges of parts, such as above the wheel cover of the fender and near the flange line of the door.

The reasons for this problem are as follows: During the deep drawing process of the metal sheet, the flange surface part is under the action of tangential compressive stress, and the sheet material wrinkles due to instability. The sheet material is retained on the surface of the stamping part through the gap between the punch and the die, forming surface waves. In addition, during the flanging process, due to the bending deformation of the material, the outer side of the bent part is subjected to tensile stress and the inner side is subjected to compressive stress. Due to the moment of these stresses, the slight warping deformation after unloading is also reflected as surface waves.

The generation of wave patterns on stamped and drawn parts is affected by factors such as product shape, material properties, and mold structure. In particular, factors such as the design of the blank holder during drawing and unreasonable mold gap will directly lead to the generation of waves.