12 Effective Solutions to Common Sheet Metal Bending Problems

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.

Reasons

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

Solutions

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

Problem 2: The workpiece is scraped after bending.

Reasons

1. unsmooth material surface
2. too small convex die bending radius
3. too small bending clearance

Solutions

1. improve the smoothness of concave die
2. increase convex die bending radius
3. adjust bending clearance

Problem 3: There are cracks at bending angles.

Reasons

1. too small bending radius
2. material grain parallel to the bending line
3. burr of workblank extending outward
4. poor remoldability of metal

Solutions

1. increase the bending radius of the convex die
2. change blanking layout
3. making burrs at the workpiece’s inner fillet
4. 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

1. employing shape bending
2. increase coverboard pressure
3. 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

1. too small convex-concave die fillet
2. too small convex-concave die clearance

Solutions

1. increase the radius of convex-concave die fillet
2. 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

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

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

Reasons

1. uneven material
2. small contact area between coverboard and material or inadequate jacking force
3. no material support device in concave die

Solutions

1. leveling materials
2. adjust material support device and increase jacking force
3. increase or correct material support device
4. 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

1. increase correction process
2. improve bending model structure to reduce material rebound

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

Reasons

1. incorrect unfolding sizes
2. material springback
3. unstable positioning

Solutions

1. calculate the work blank size accurately
2. increase correction process or improve bending die structure
3. 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

1. increase the height of the workpiece to be bent
2. 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

1. increase bending pressure
2. increase correction process
3. 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

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