Bending and forming of the metal sheet are carried out on a plate bending machine.

Put the workpiece on the plate bending machine, use the lifting lever to lift the brake block, then make the workpiece slide to a proper position, and then down the brake block to the workpieces, and further press on the bending lever to realize the bending of the metal sheet.

The minimum bending radius is a function of the ductility and thickness of the metal formed.

For aluminum sheet metal, the bending radius is greater than the thickness of the plate.

Due to the elasticity, the bending angle of metal is slightly bigger than the angle required.

The bending of the metal sheet is conducted in a metal processing workshop.

Metal sheet processing is only a series of processing techniques for bending, riveting, and welding metal materials.

The problems that occurred in this process and the corresponding solutions are discussed below.

Table of Contents

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

**Reasons**

- no line pressing or pre-bending.
- inadequate material pressure
- dissymmetric convex-concave die fillet and uneven bending pressure
- low height

**Solutions**

- design line pressing or pre-bending techniques
- increase jacking force
- even clearance in the convex-concave die and polish fillet
- make the height larger or equal to the minimum size

**Problem 2:** **The workpiece is scraped after bending.**

**Reasons**

- unsmooth material surface
- too small convex die bending radius
- too small bending clearance

**Solutions**

- improve the smoothness of concave die
- increase convex die bending radius
- adjust bending clearance

**Problem 3:** **There are cracks at bending angles.**

**Reasons**

- too small bending radius
- material grain parallel to the bending line
- burr of workblank extending outward
- poor remoldability of metal

**Solutions**

- increase the bending radius of the convex die
- change blanking layout
- making burrs at the workpiece’s inner fillet
- annealing or using soft material

**Problem 4: Bending causes hole deformation**

**Reasons**

When the elastic bending is used to positioning the hole, the outside of the bending arm is pulled by friction on the surface of the concave mold and the outer surface of the workpiece, making the positioning hole deformed.

**Solutions**

- employing shape bending
- increase coverboard pressure
- add pitting plaid to coverboard to increase friction so as to prevent the workpiece from sliding when bending

**Problem 5: ****The bending surface is thinner.**

**Reasons**

- too small convex-concave die fillet
- too small convex-concave die clearance

**Solutions**

- increase the radius of convex-concave die fillet
- adjust the convex-concave die clearance

**Problem 6:** **The workpiece surface is bulging or uneven.**

**Reasons**

Under the tension in the circumferential direction, the outer surface of the material shrinks while the inner surface extends during bending, and forming bulging in the bending direction.

**Solutions**

- provide adequate pressure to convex-concave die at the final stamping stage
- make concave round angle radius equal to that of the workpiece’s excircle
- optimize techniques

**Problem 7: The concave part is uneven at the bottom.**

**Reasons**

- uneven material
- small contact area between coverboard and material or inadequate jacking force
- no material support device in concave die

**Solutions**

- leveling materials
- adjust material support device and increase jacking force
- increase or correct material support device
- increase the shaping processes

**Problem 8: The axis of holes on two sides are misaligned after bending. **

**Reasons**

The material rebound changes the bending angle, making the central line misaligned.

**Solutions**

- increase correction process
- improve bending model structure to reduce material rebound

**Problem 9: The precise hole position cannot be guaranteed after bending.**

**Reasons**

- incorrect unfolding sizes
- material springback
- unstable positioning

**Solutions**

- calculate the work blank size accurately
- increase correction process or improve bending die structure
- change processing methods or improve positioning

**Problem 10:** **The bending line is not parallel to the two-hole center.**

**Reasons**

When the bending height is less than the minimum bending height, the bending part occurs expansion.

**Solutions**

- increase the height of the workpiece to be bent
- improve bending techniques

**Problem 11: Deformation occurs in terms of width after bending (the bending part occurs bow deflection in width).**

**Reasons**

The inconsistent depth and shrinkage in the width of the workpiece cause torsion and deflection.

**Solutions**

- increase bending pressure
- increase correction process
- ensure a certain angle between materials and bending direction

**Problem 12: Workpiece with incision occur downward deflection.**

**Reasons**

The incision makes the two straight edges open to the left and right side, forming deflection at the bottom.

**Solutions**

- improve the workpiece structure
- increase processing allowance at incisions to connect incisions and then cut off the process after bending

EmilyIn the first passage, you write “brake black” in the third line. Maybe it is a small error.

MachineMfgthanks, it has been revised.

Taylor BishopI wanted to thank you for explaining some solutions to some sheet metal bending problems. I didn’t know that a scraped workpiece could be fixed by improving the smoothness of concave die. I wouldn’t mind learning how this could be done or how to determine how much smoothness is needed.

MachineMfgWe will keep updating the post, so stay turned.

HemrajIf lh cylinder of 250 ton bending is not working then whats a problem in that cylinder?

MachineMfgPls refer to this article about press brake troubleshooting:

https://www.machinemfg.com/press-brake-bending-problems-and-solutions/

HASIBWhat is bending clearance? Please explain it deeply…

Bill LewisI have worked in sheet metal fabrication for the past 31 years. Honestly I don’t know where you come up with your list of 12 common bending problems, but I must tell you that you have completely missed the number 1 bending error. It is “parts bent backwards”. If “parts bent backwards” is not your number 1 problem, please explain what you did to drive it further down your list to a point that it doesn’t make your top 12.

ShaneAnybody have comments for this?