The bending and forming of metal sheets are carried out on the bending machine. Place the workpiece to be formed on the bending machine, use the lifting lever to lift the brake shoe, 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 formed metal. For aluminum plates, the bending radius of the metal is larger than the thickness of the plate. When bending, due to a certain degree of rebound, the angle at which the metal is bent is slightly larger than the required angle. The bending of metal sheets is carried out in metal processing 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 during sheet metal processing.
Problem 1: The bent edge is not straight and the size is unstable
reason:
1. The design process does not include crimping or pre-bending.
2. The material pressing force is not enough
3. The rounded corners of the convex and concave molds have asymmetric wear or the bending force is uneven.
4. The height size is too small
Solution:
1. Design crimping or pre-bending process
2. Increase the pressing force
3. The gap between the convex and concave molds is even and the rounded corners are 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
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 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 corners
reason:
1. The inner radius of the bend is too small
2. The grain direction of the material is parallel to the bending line
3. The burr side of the blank faces outward.
4. Metal plasticity is poor
Solution:
1. Increase the bending radius of the punch
2. Change blanking layout
3. Change the burrs to the inner fillet of the part
4. Annealing or using soft materials
Problem 4: Bending causes hole deformation
Reason: When elastic bending is used and hole positioning is used, the outside of the bend arm is stretched due to friction between the surface of the die and the outer surface of the workpiece, causing the positioning hole to deform.
Solution:
1. Use shape bending
2. Increase the pressure of the ejection plate
3. Add pitted patterns on the top plate to increase friction and prevent the parts from slipping when bending.
Problem 5: The extruded material on the curved surface becomes thinner
reason:
1. The rounded corners of the concave mold are too small
2. The gap between the convex and concave molds is too small
Solution:
1. Increase the radius of the die fillet
2. Correct the gap between convex and concave molds
Problem 6: The end surface of the part is bulging or uneven
reason:
1. When bending, the outer surface of the material is stretched in the circumferential direction and produces shrinkage deformation, and the inner surface is compressed in the circumferential direction and produces elongation deformation. Therefore, the deflection end surface appears to bulge along the bending direction.
Solution:
1. The convex and concave molds should have sufficient pressure in the final stage of stamping.
2. Make the fillet radius of the die corresponding to the outer corner of the part
3. Increase process improvement
Problem 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 material pushing force is insufficient.
3. There is no ejection device in the die
Solution:
1. Leveling materials
2. Adjust the ejection device to increase the ejection force
3. Add ejection device or correction
4. Adding and shaping process
Problem 8: After bending, the axes of the two holes facing each other are misaligned.
Reason: The material rebounds and changes the bending angle, causing the center line to shift.
Solution:
1. Add calibration process
2. Improve the bending die structure to reduce material rebound
Problem 9: The hole position and dimensional accuracy cannot be guaranteed after bending
reason:
1. The expanded size of the parts is wrong
2. Caused by material rebound
3. Unstable positioning
Solution:
1. Accurately calculate the blank size
2. Add correction process or improve the bending mold forming structure
3. Change process processing methods or increase process positioning
Problem 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 expand.
Solution:
1. Increase the height dimension of the bending parts
2. Improve the process method of bending parts
Problem 11: Deformation in the width direction after bending, and bow deflection in the width direction of the bent part
Reason: Torsion and deflection occur due to inconsistent drawing and shrinkage in the width direction of the part
Solution:
1. Increase bending pressure
2. Add calibration process
3. Ensure that the grain direction of the material has a certain angle with the bending direction.
Problem 12: Parts with cuts deflect downwards
Reason: The incision causes the two straight edges to open to the left and right, causing deflection at the bottom of the part
Solution:
1. Improve the structure of parts
2. Add process allowance to the incisions to connect them, and then cut off the process allowance after bending.
