12 questions about sheet metal bending technology

12 questions about sheet metal bending technology

The bending and forming of the metal sheet is carried out on the bending machine, the workpiece to be formed is placed on the bending machine, the brake shoe is lifted with the lifting lever, the workpiece is slid to the appropriate position, and then the brake shoe is lowered to the desired position. On the formed workpiece, the bending of metal is realized by applying force to the bending lever on the bending machine. The minimum bend radius is a function of the ductility and thickness of the formed metal. For aluminum sheets, the bending radius of the metal is greater than the thickness of the sheet. When bending, due to certain springback, the bending angle of the metal is slightly larger than the required angle. The bending of sheet metal is carried out in a metal workshop.

Avoid the sting of poor practices in sheet metal bendingSheet metal processing is just a series of processes such as bending, riveting, and welding of metal materials. The following is a description of the problems and solutions that may be encountered during the bending process in sheet metal processing.

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


1. The design process does not arrange crimping or pre-bending

2. The material pressing force is not enough

3. Asymmetric wear of convex and concave die fillets or uneven bending force

4, the height size is too small


1. Design crimping or pre-bending process

2. Increase the pressing force

3. Uniform gap between convex and concave die, rounded corner polishing

4. The height size cannot be less than the minimum limit size

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


1. The surface of the raw material is not smooth

2. The bending radius of the punch is too small

3. The bending gap is too small


1. Improve the finish of the punch and die

2. Increase the bending radius of the punch

3. Adjust the bending gap

Problem 3: There are cracks in the bending corners


1. The inner radius of the bending is too small

2. The grain direction of the material is parallel to the bending line

3. The burr side of the blank faces outwards

4. Metal plasticity is poor


1. Increase the bending radius of the punch

2. Change the blanking layout

3. The burr is changed to the inner fillet of the workpiece

4. Annealed or soft material

Problem 4: Bending causes hole deformation

Reason: When the elastic bending is adopted and the hole is positioned, the outer side of the bending arm is pulled due to the friction between the surface of the die and the outer surface of the workpiece, which deforms the positioning hole.


1, using shape bending

2. Increase the pressure of the top plate

3. Add pockmarks on the top plate to increase friction and prevent the workpiece from slipping during bending

Problem 5: Thinning of the extrusion material on the curved surface


1. The fillet of the die is too small

2. The gap between the convex and concave die is too small


1. Increase the radius of the die fillet

2. Correct the gap between punch and die

Question 6: The end face of the part is bulging or uneven

Reason: When bending, the outer surface of the material is stretched in the circumferential direction to produce shrinkage deformation, and the inner surface is compressed in the circumferential direction to produce elongation deformation, so the bending end face bulges along the bending direction.


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

2. Make the die fillet radius corresponding to the outer fillet of the workpiece

3. Increase the process improvement

Problem 7: The bottom of the concave part is not flat


1. The material itself is not flat

2. The contact area between the top plate and the material is small or the top material force is not enough

3. There is no ejector device in the die


1. Leveling material

2. Adjust the ejecting device to increase the ejecting force

3. Increase the top material device or correct

4. Add shaping process

Question 8: The axes of the two opposite holes on both sides are displaced after bending

Reason: The springback of the material changes the bending angle, causing the centerline to shift


1. Increase the calibration process

2. Improve bending die structure to reduce material springback

Question 9: The dimensional accuracy of the hole position cannot be guaranteed after bending


1. The size of the parts is incorrect

2. Caused by material rebound

3. Positioning is unstable


1. Accurately calculate the blank size

2. Increase the correction process or improve the bending die forming structure

3. Change the processing method or increase the process positioning

Question 10: The bending line is not parallel to the connection between the center of the two holes

Reason: When the bending height is less than the minimum bending limit height, the bending part will bulge


1. Increase the height of the bending part

2. Improve the process method of bending parts

Question 11: After bending, the width direction is deformed, and the bent part has bow deflection in the width direction

Reason: torsion and deflection due to inconsistent drawing and shrinkage in the width direction of the workpiece


1. Increase the bending pressure

2. Increase the calibration process

3. Ensure that the grain direction of the material has a certain angle with the bending direction

Problem 12: The part with the cut-out flexes downwards

Reason: The incision makes the two straight sides open to the left and right, and the bottom of the part is deflected


1. Improve the structure of parts

2. Increase the process allowance at the incision to connect the incisions, and then cut off the process allowance after bending.

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