Cracks on the flange extension side wall of the ho

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Mold flange extension sidewall crack

when the flange extends, if the material flow is blocked, cracks will occur because the deformation of the sidewall exceeds the limit

causes and elimination methods

(1) product shape

① punch fillet radius (RP) is too small

increase the flange fillet radius (RP), resulting in the condition that the material can flow from the RP part. In order to meet the requirements of the drawing, a finishing process can be added

② the corner fillet radius (RC) is too small

compared with the drawing depth, when the corner fillet radius (RC) is too small, the above defects will also occur, so changing RC should be considered as one of the measures. Of course, RC will change the shape of the product if it is too large, but when the unchanged RC cannot be formed, it must be changed. Therefore, the physical meaning of softening point is not as clear as glass transition temperature RC

(2) stamping conditions

① the blank holder force is too large

if the blank holder force is too large to restrict the inflow of material, the above defects will occur. Therefore, it is necessary to reduce the blank holder force as long as the flange does not wrinkle

② the concave die surface is poorly lubricated

in order to promote the inflow of materials, a thin layer of high viscosity lubricating oil should be applied

③ poor blank shape

The shape of the blank and the shape and position of the process hole are very important. When the flange area is reduced, edge cracks will occur, and when the flange area is too large, sidewall cracks will occur. Therefore, we must find the best value between the two

according to experience, making the flange larger can form a wide range, which is suitable for mass production. At first, we made the shape of the flange into a concave shape, but due to the unstable forming accuracy, finally, we used a square blank and stretched it with a drawbead

but the volume of the seal is changing

④ incision timing

if the time of incision is too late, the above defects will also occur. The elimination method is to reduce the punch height and quickly make efforts to promote the development of the industry when verifying the compliance of food contact materials

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