The bending and forming of metal sheets are carried out on the bending machine. Place the workpiece to be formed on the bending machine, lift the brake shoe with the lifting lever, slide the workpiece to the appropriate position, and then lower the brake shoe to the desired position. On the formed workpiece, the metal is bent and formed 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 metal being formed. For aluminum sheets, the bending radius of the metal is greater than the thickness of the sheet. When bending, due to a certain rebound, the angle of metal bending is slightly larger than the required angle. Bending of sheet metal is carried out in metalworking workshops.
Sheet metal processing is just a series of processes such as bending, riveting, and welding of metal materials. The following are the problems and solutions encountered in the bending process in sheet metal processing.
Problem 1: The bending edge is not straight and the size is unstable
reason:
1. The design process does not arrange crimping or pre-bending
2. The pressing force of the material is not enough
3. The rounded corners of the convex and concave dies are asymmetrically worn or the bending force is uneven
4. The height is too small
Solution:
1. Design crimping or pre-bending process
2. Increase the pressing force
3. The gap between the convex and concave dies is uniform, and the rounded corners are polished
4. The height size cannot be smaller than the minimum limit size
Problem 2: The outer surface of the workpiece is scratched after bending
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 smoothness of the convex and concave molds
2. Increase the bending radius of the punch
3. Adjust the bending gap
Problem 3: There are cracks in the bending corner
reason:
1. The inner bending radius is too small
2. The grain direction of the material is parallel to the bending line
3. The burrs of the blank face outward
4. Poor metal plasticity
Solution:
1. Increase the bending radius of the punch
2. Change blanking layout
3. The burr is changed to the fillet of the workpiece
4. Annealing or using soft materials
Question 4: Bending causes hole deformation
Reason: When using elastic bending and positioning with holes, 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 part, which deforms the positioning hole.
Solution:
1. Using shape bending
2. Increase the pressure of the ejector plate
3. Add pockmarks on the top material plate to increase friction and prevent parts from slipping when bending
Problem 5: Extrusion material on curved surface becomes thinner
reason:
1. Die fillet is too small
2. The gap between the convex and concave dies is too small
Solution:
1. Increase the fillet radius of the die
2. Correct the gap between punch and die
Question 6: The end face of the workpiece is bulging or uneven
reason:
1. 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 deflection end surface appears bulging along the bending direction.
Solution:
1. The punch and die should have enough pressure in the final stage of stamping
2. Make the die fillet radius corresponding to the outer fillet of the workpiece
3. Increase process improvement
Question 7: The bottom of the concave part is uneven
reason:
1. The material itself is uneven
2. The contact area between the top plate and the material is small or the force of the top material is not enough
3. There is no jacking device in the die
Solution:
1. Leveling material
2. Adjust the jacking device to increase the jacking force
3. Add jacking device or correction
4. Add shaping process
Question 8: After bending, the axes of the two opposite holes are shifted
Reason: Material springback changes the bending angle to misalign the center line
Solution:
1. Increase the calibration process
2. Improve the structure of the bending die to reduce the springback of the material
Question 9: The accuracy of the hole position and size cannot be guaranteed after bending
reason:
1. The expanded size of the workpiece is wrong
2. Material rebound caused by
3. Unstable positioning
Solution:
1. Accurately calculate the blank size
2. Increase the correction process or improve the bending die forming structure
3. Change the process processing method or increase the process positioning
Question 10: 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 bulge outward
Solution:
1. Increase the height of bending parts
2. Improve the bending process method
Question 11: After bending, the width direction is deformed, and the bent part appears bow-shaped deflection in the width direction
Reason: torsion and deflection due to inconsistent drawing and shrinkage in the width direction of the part
Solution:
1. Increase 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: Parts with notches deflect downward
Reason: The incision makes the two straight sides open to the left and right, and the bottom of the part has deflection
Solution:
1. Improve the structure of the parts
2. Increase the process allowance at the incision to connect the incisions, and then cut off the process allowance after bending
