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What is the reason for the wrinkling and cracking of automobile covering tensile parts?

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The direct reason for the cracking of the workpiece is that the tensile deformation resistance is higher than the actual effective tensile strength of the material at the simple wall crack. The appropriate adjustment method to completely eliminate the breakage of the puller is as follows:

(1) Adjust the pressing material pressure and reduce the pressure.

(2) Adjust the stretching gap to make the gap larger and more uniform.

(3) Adjust the radius of the mold fillet. If the radius of the mold fillet is too small, the parts are easy to crack. Increasing the die fillet radius can reduce the degree of pull cracking.

(4) Adjust the radius of the die fillet.

(5), adjust the relative position of punch and die.

(6) The size of the blank is too large or the shape is incorrect, and the quality and lubrication of the plate may also cause the parts to crack. The size or shape of the blank should be changed, and the stamping process should be adjusted.

There are many reasons why parts can crack. When adjusting, carefully check the state and position of the crack, determine the stroke position of the crack, infer the cause of the crack according to the specific situation, and then work out a specific solution to the crack.

Some experience in solving trial wrinkling and cracking.

During the initial deep drawing of the drawing die, the drawn parts are generally wrinkled and cracked. At this time, it is necessary to carefully observe the condition of the pressing surface and analyze the various causes of wrinkles. If there are indentations on the pressing surface and cracks at the radius of the concave die, it means that feeding is difficult; if the pressing surface is corrugated, it is easy to feed. Later, due to the generation of material corrugations, it is difficult to flow, resulting in wrinkling and cracking, that is, the material is difficult to flow during the stretching process, which will cause wrinkling and cracking during the stretching process, so different situations should be solved by different methods.

Feeding difficulties are usually caused by excessive binder resistance. If the surface roughness of the binder surface and the die fillet is too high, or there is recoil forming and local stretching is too large, it is necessary to adjust the outer slider, reduce the blank holder force, and appropriately increase the die fillet. Reduce the surface convexity and appropriately increase the lacing clearance. If the local tensile deformation is too large and inversion occurs, it should be solved by adding process gaps or process holes.

The feeding is easy, mainly because the feeding resistance is too small, the contact of the pressing surface is poor, or the design process performance of the drawing part is poor. If it is a binder surface problem, the binder surface needs to be ground to ensure adequate contact. In addition, the outer slider can be adjusted to increase the blank holder force or increase the blank holder area. If the process performance of the stretched part is not good, it is necessary to redesign the stretched part to make it a qualified product.

The above only discusses how to prevent or solve the wrinkling problem of the cover from the aspects of technology, drawing die design and adjustment. There are many reasons for the wrinkling and cracking of the cover. But as long as the phenomenon is carefully studied and classified, different situations can be solved in different ways, resulting in a coating of good surface quality. Hope the above content can be helpful to readers.

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