Tips for L-bends, N-bends, Z-bends, Offset-bends and Other Special Bends

1. L bend

L bend

According to angle, it can divide into 90˚bend and non 90°bend.

According to processing, it can be divided into general processing (L> V / 2) and special processing (L <V / 2).

1>. The mold is selected according to material, plate thickness and forming angle.

2>. Leaning Principle

1) Based on the principle of two back stoppers and positioning based on the shape of the work piece.

2) When a back gauge is in place, pay attention to deflection, and it is required to be on the same center line as the bending size of the work piece.

3) For small bends, it is better to process them in reverse positioning.

4) It is better to set under the middle of the back gauge. (The back gauge is not easy to lift when leaning in)

5) It is better to be close to the back gauge.

6) It is better to lean with the long side.

7) Assist with jig (leaning irregular position with hypotenuse)

3>. Precautions

  1. Pay attention to the positioning way during processing and the movement way of back initiating structure in various positioning processing methods.
  2. The mold is bent when it is being installed, and the back initiating structure is drawn back to prevent the workpiece from deforming during bending.
  3. When the large workpiece is bent internally, because the workpiece has a larger shape and a smaller bending area, it is difficult for the tool and the bending area to overlap, resulting in difficult positioning of the work piece or damage to the bent work piece. In order to avoid the above situation, a positioning point can be added in the longitudinal direction of the processing. Processing in two directions in this way facilitates processing and positioning, improves processing safety, prevents work piece damage, and improves production efficiency.

2. N bend

N bend

N-bend should adopt different processing methods according to different shapes. When bending, its internal dimensions must be greater than 4mm, and the size of the X dimension is limited due to the mold shape. If the material size is less than 4mm, special methods are used for processing.

1>. Choose the mold according to the thickness of the material, size, material and bending angle.

2>. Leaning Principle

1) Ensure that the work piece does not interfere with the tools.

2) Ensure that the leaning angle is slightly less than 90°.

3) It is best to use two back initiating structures to lean, except in special cases.

3>. Precautions

1) After the bend is L-bended, the expected angle should be 90° or slightly less than 90° to facilitate processing and positioning.

2) During the second bend processing, the seating position is required to be centered on the processing surface.

3. Z bend

Z bend

Also known as the offset bending, that is, the bend in the reverse direction. Divide the hypotenuse and straight edge differences based on the angle. The minimum size of the bending process is limited by the processing mold, and the maximum size is determined by the shape of the processing machine. In general, when the inner size of the Z-bend is less than 3.5T, an offset die is used. When it is larger than 3.5T, the normal processing method is adopted.

1>. Leaning Principle

1) Convenient leaning position and good stability.

2) Generally, the leaning position is the same as the L bending.

3) The second leaning position requires the work piece to be flush with the lower die.

2>. Precautions

1) The processing angle of the L bending must be in place, and the general requirement is 89.5° to 90°.

2) Pay attention to the deformation of the workpiece when pulling back.

3) The order of processing must be correct.

4) For special processing, the following methods can be used for processing:

– Center line separation method (eccentric machining)

– Small V machining (need to increase the bending factor)

– Easy mold forming

– Grinding the lower mold

4. Acute bending and Hemming

Acute bending and Hemming

The processing steps of acute bending and hemming are:

  1. First bend and insert to a depth of about 35°.
  2. Then use a Hemming die to flatten to the flat and close.

1>. Mode selection

According to 5 to 6 times the material thickness, select the V groove width of the lower die with a depth of 30°, and select the upper die according to the specific conditions of the flattening edge.

2>. Precautions

The flattening side should pay attention to the parallelism of the two sides. When the flattening side processing size is longer, the flattened side can be bent first and then flattened. For shorter flattening edges, padding processing is available.

5. Press Hardware 

The use of a press brake to press the riveted hardware generally requires the use of concave molds, fixtures and other auxiliary mold processing. Generally, there are crimp nuts, studs, screws, and other hardware.


  1. When the shape of the workpiece needs to be avoided, it must do the avoidance processing.
  2. After processing, check the torque, whether the thrust reaches the standard and whether the hardware and the workpiece are flat and close.
  3. After pressing and riveting after bending, when pressing next to the machine, pay attention to the avoidance of processing and the parallelism of the mold.
  4. If it is bulging, pay attention to that there must be no cracks on the bulging edge, and the bulging edge cannot be higher than the workpiece surface.

6. Special mold forming

Special mold forming

The processing of general special mold forming includes:

Small offsets, hooks, draw bridges, draw bags, squashes and some irregular shapes.

Special mold is generally positioning by back gauge fingers or just do the self-positioning.

The processing of the above content with special mold is most important that its functions and assembly requirements are not affected and the appearance is normal.

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