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Summary of 12 technical problems in sheet metal forming

Issuing time:2021-11-27 17:33

Problem 1: the bending edge is not straight and the size is unstable.


1. There is no crimping or pre bending in the design process.

2. Insufficient pressing force

3. The fillet wear of punch and die is asymmetric or the bending stress is uneven.

4. The height dimension is too small


1. Design wire pressing or pre bending process.

2. Increase the pressure.

3. The clearance between male and female dies shall be uniform and the fillet shall be polished.

4. The height dimension shall not be less than the minimum limit dimension.


Problem 2: the outer surface of the workpiece is scratched after bending.


1. The surface of raw materials is not smooth.

2. The bending radius of punch is too small.

3. The bending clearance is too small.


1. Improve the finish of punch and die.

2. Increase the bending radius of the punch

3. Adjust bending clearance

Question 3: crack in bending angle.


1. The inner radius of bending is too small.

2. The direction of material particles is parallel to the bending curve

3. The burr surface of the blank faces outward.

4. Poor metal plasticity


1. Increase the bending radius of the punch

2. Change blanking layout

3. The burr becomes the fillet of the part.

4. Anneal or use soft materials

Problem 4: hole deformation caused by bending


During elastic pressure bending and hole positioning, due to the friction between the die surface and the outer surface of the workpiece, the outside of the bending arm is pulled, resulting in the deformation of the positioning hole.


1. Using shape bending

2. Increase the pressure of the ejector plate

3. Add dent squares on the ejector plate to increase friction and prevent parts from slipping during bending.

Problem 5: the extruded material on the surface becomes thinner.


1. The die fillet is too small.

2. The gap between male and female molds is too small.


1. Increase the fillet radius of the die

2. Correct the gap between male mold and female mold

Problem 6: the end face of the part is bulging or uneven.


1. During bending, the outer surface of the material shrinks and deforms in the circumferential tension, and the inner surface elongates and deforms in the circumferential compression, resulting in bulging of the bending end face along the bending direction.


1. The punch and die of the workpiece should have sufficient pressure in the final stage of stamping.

2. Make the fillet radius of the die correspond to the fillet of the part.

3. Improve the process.

Question 7: the bottom of the recess is uneven.


1. The material itself is uneven.

2. The contact area between the top plate and the material is small or the jacking force is insufficient.

3. There is no ejector in the female mold.


1. Leveling materials

2. Adjust the jacking device to increase the jacking force.

3. Add jacking device or correct.

4. Add molding process.

Question 8: after bending, the axes of two opposite holes are not aligned.


The material springback changes the bending angle and offsets the centerline.


1. Add calibration procedure.

2. Improve the structure of bending die to reduce material springback.

Question 9: the accuracy of hole position and size cannot be guaranteed after bending.


1. The expanded size of parts is wrong.

2. Caused by material rebound

3. Unstable positioning


1. Accurate calculation of blank size

2. Add correction program or improve the forming structure of bending die.

3. Change the processing method or add process positioning.

Question 10: the bending curve is not parallel to the centerline of the two holes.


When the bending height is less than the minimum bending limit height, the bending part will protrude.


1. Increase the height dimension of the bending part.

2. Improve the processing method of bending parts.

Question 11: after bending, it deforms in the width direction, and the bending part has bow deflection in the width direction.


Torsion and deflection will occur due to inconsistent stretching and contraction in the width direction of the workpiece.


1. Increase bending pressure

2. Add calibration procedure.

3. Ensure that there is a certain angle between the material particle direction and the bending direction.

Q12: notched parts bend downward.


Cutting makes the two straight edges open to the left and right, and the bottom of the part deflects.


1. Improve part structure.

2. Add process allowance at the notch, connect the notch, and cut off the process allowance after bending.

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