12 major problems of sheet metal bending and forming technology

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

the reason:

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

2. The material pressing force is not enough

3. The rounded corners of the convex and concave molds wear asymmetrically or the bending force is uneven

4. The height dimension is too small

Solution:

1. Design pressing or pre-bending process

2. Increase the pressing force

3. Uniform gap between convex and concave molds, rounded corners polished

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

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

the reason:

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

Solution:

1. Improve the finish of convex and concave molds

2. Increase the bending radius of the punch

3. Adjust the bending gap

Problem 3: Cracks in the bending corner

the reason:

1. The inner radius of the bend is too small

2. The material pattern is parallel to the bending line

3. The burr of the blank faces outwards

4. Poor metal plasticity

Solution:

1. Increase the bending radius of the punch

2. Change the blanking layout

3. The burr is changed to the fillet in the part

4. Anneal or use soft materials

Problem 4: Deformation of the hole caused by bending

Reason: When using elastic bending and positioning with holes, the outside 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.

Solution:

1. Use shape bending

2. Increase the pressure of the top plate

3. Add pitting grid pattern on the top plate to increase the friction and prevent the part from slipping when bending

Problem five: thinning of the extrusion material on the curved surface

the reason:

1. The fillet of the die is too small

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

Solution:

1. Increase the corner radius of the die

2. Correct the gap between convex and concave molds

Problem 6: The end face of the workpiece is bulging or uneven

the reason:

1. When bending, the outer surface of the material is stretched in the circumferential direction to produce shrinkage and deformation, and the inner surface is compressed in the circumferential direction to produce elongation and deformation, so the swelling phenomenon occurs on the flexural end surface along the bending direction.

Solution:

1. The convex and concave dies should have enough pressure in the final stage of stamping

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

3. Increase process improvement

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

the reason:

1. The material itself is not flat

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

3. No ejector device in the cavity

Solution:

1. Leveling materials

2. Adjust the ejecting device to increase the ejecting force

3. Add ejector device or correction

4. Add shaping process

Problem 8: The axis of the two holes facing each other is misplaced after bending

Reason: Material springback changes the bending angle to make the centerline shift

Solution:

1. Increase the calibration process

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

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

the reason:

1. The unfolded size of the part is incorrect

2. Caused by material rebound

3. Unstable positioning

Solution:

1. Accurately calculate the size of the blank

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

3. Change process method or increase process positioning

Problem ten: The bending line is not parallel to the center line of the two holes

Reason: when the bending height is less than the minimum bending limit height, the bending part will expand outwardly

Solution:

1. Increase the height of the bending parts

2. Improve the process method of bending parts

Question 11: Deformation in the width direction after bending, and bow deflection in the width direction of the bent part

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

Solution:

1. Increase bending pressure

2. Increase the calibration process

3. Ensure that the material grain and bending direction have a certain angle

Question twelve: the part with notch flexes downwards

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

Solution:

1. Improve the structure of parts

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