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Complete Solutions of Press Brake Bending Problems | FAQ

The press brake machine is the important equipment for bending and forming workpieces in the sheet metal processing, which can bend the sheet metal to different shapes according to customer’s requests.

After long-term use of the press brake machine, machine problems are inevitable. Below are the problems and solutions encountered in the bending process.

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


- The design process not include crimping or pre-bending.

- The material pressing force is not enough.

- The press brake upper and lower die tip is worn and asymmetrical, or uneven bending force.

- The height size is too small.


- Design crimping or pre-bending process.

- Increase the pressing force.

- The gap between the upper and lower die uniform, and the rounded corner polished.

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

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


- The surface of the raw material is not smooth.

- The bending radius of the upper die is too small.

- The bending gap is too small.


- Improve the smoothnessof the punch and die.

- Increase the bending radius of the punch.

- Adjust the bending gap.

Problem 3: There are cracks in the bending angles


- The inner radius of the bending is too small.

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

- The burr change to be at the inner of the workpiece.

- Metal plasticity is poor.


- Increase the bending radius of the punch.

- Change the blanking layout.

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

- Annealed or using soft material.

Problem 4: Bending causes holes deformation


Press brake machine adopt elastic bending, and locate by the holes position. The outer side of the bending arm is pulled due to the friction between the surface of the bottom die and the outer surface of the workpiece, so that the positioning hole is deformed.


- Using shape bending.

- Increase the pressure of the top plate.

- Add pockmarks on the top plate to increase friction,which will prevent the workpiece from slipping during bending.

Problem 5: The curved material surfaces to be thin


- The radius angle of the lower die is too small.

- The gap between the upper and lower die is too small.


- Increase the radius angle of the lower die.

- Correct the gap between the upper and lower die.

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

CNC Press Brake Workpiece


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


- The upper and lower die should have sufficient pressure in the final stage of forming.

- Make the lower die with correct radius angle corresponding to the outer radius angle of the workpiece.

- Increase the process improvement.

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


- The material itself is not flat.

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

- There is no ejector device in the die.


- Leveling material.

- Adjust the ejecting device to increase the ejecting force.

- Increase the ejectingdevice or correctit.

- Add the bent workpiece shaping process.

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


- The bent material springs back, which changes the bending angle, and shifts the centerline.


- Increase the calibration process.

- Improve forming tool structure, which can reduce material springback.

Problem 9: The position size and accuracy of the hole can not be guaranteed after bending


- The expansion size of the workpieceis incorrect.

- Caused by the bent material rebound.

- Positioning is unstable.


- Accurately calculate the workblank size.

- Increase the correction process or improve the bending tool forming structure.

- Change the processing method or increase the process positioning.

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



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


- Increase the height of the workpiece which need to be bent.

- Improve the process method of bending workpiece.

Problem 11: After bending, the width direction of the bending part is deformed, and in the width direction the bent part has bow-shaped deflection


- Because of the workpiece inconsistent drawing and shrinkage in the width direction, the bending part caused to torsion and deflection.


- Increase the bending pressure.

- Increase the calibration process.

- Make surethat the grain direction of the material has a certain angle with the bending direction.

Problem 12: The bending part with notches, has a downwards direction deflection


- The notches makes the two straight sides open to the left and right, and the bottom of the workpiece has a deflection.


- Improve the workpiece structure.

- Increase the process allowance at the notch postion, which will connect the notches, and then cut off the process allowance after bending.

Wuxi Shenchong has been dedicated to sheet metal machines, such as press brake, shearing and rolling machines for more than 20 years. If you have any needs, please feel free to contact our company.