Metal sheets are bent and formed using a plate bending machine. The workpiece is placed on the machine and the lifting lever is used to lift the brake block, which allows the workpiece to be positioned. The brake block is then lowered onto the workpiece, and the bending lever is pressed to bend the metal sheet.
The minimum bending radius is determined by the ductility and thickness of the metal being formed. For aluminum sheet metal, the bending radius should be greater than the thickness of the plate.
Due to elasticity, the bending angle of the metal is slightly greater than the required angle.
The bending of metal sheets is typically carried out in a metal processing workshop. Metal sheet processing involves a series of techniques, such as bending, riveting, and welding of metal materials. The common problems that occur during this process and their corresponding solutions are discussed below.
Problem 1: The bending edge is not straight and the size is unstable.
- no line pressing or pre-bending.
- inadequate material pressure
- dissymmetric convex-concave die fillet and uneven bending pressure
- low height
- 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.
- unsmooth material surface
- too small convex die bending radius
- too small bending clearance
- improve the smoothness of concave die
- increase convex die bending radius
- adjust bending clearance
Problem 3: There are cracks at bending angles.
- too small bending radius
- material grain parallel to the bending line
- burr of workblank extending outward
- poor remoldability of metal
- 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
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.
- 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.
- too small convex-concave die fillet
- too small convex-concave die clearance
- increase the radius of convex-concave die fillet
- adjust the convex-concave die clearance
Problem 6: The workpiece surface is bulging or uneven.
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.
- 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.
- uneven material
- small contact area between coverboard and material or inadequate jacking force
- no material support device in concave die
- 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.
The material rebound changes the bending angle, making the central line misaligned.
- increase correction process
- improve bending model structure to reduce material rebound
Problem 9: The precise hole position cannot be guaranteed after bending.
- incorrect unfolding sizes
- material springback
- unstable positioning
- 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.
When the bending height is less than the minimum bending height, the bending part occurs expansion.
- 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).
The inconsistent depth and shrinkage in the width of the workpiece cause torsion and deflection.
- increase bending pressure
- increase correction process
- ensure a certain angle between materials and bending direction
Problem 12: Workpiece with incision occur downward deflection.
The incision makes the two straight edges open to the left and right side, forming deflection at the bottom.
- improve the workpiece structure
- increase processing allowance at incisions to connect incisions and then cut off the process after bending
9 thoughts on “12 Effective Solutions to Common Sheet Metal Bending Problems”
In the first passage, you write “brake black” in the third line. Maybe it is a small error.
thanks, it has been revised.
I 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.
We will keep updating the post, so stay turned.
If lh cylinder of 250 ton bending is not working then whats a problem in that cylinder?
Pls refer to this article about press brake troubleshooting:
What is bending clearance? Please explain it deeply…
I 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.
Anybody have comments for this?