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5 Points to note for bending pipes of cold bending

Cold bending of bending pipes

Tube design

  • When designing and arranging pipes, avoid excessive arcs, arbitrary curves, compound bends, and arcs greater than 180°.
  • Excessive arc not only makes the tooling bulky, but also is limited by the size of the pipe bending machine;
  • The design of arbitrary curves and compound curves is very unreasonable, which greatly hinders mechanization and automated production, making it difficult for operators to get rid of heavy manual labor;
  • The arc greater than 180° makes the bending machine unable to unload the mold.
Cold bending of bending pipes
Cold bending of bending pipes


Radius standardization

The bending radius should try to achieve “one tube, one mold” and “multiple tubes, one mold”.
Regarding a pipe, no matter how many bends and bending angles, there can only be one bending radius, because the pipe bender does not replace the module during the bending process, this is “one pipe, one mold”. “Multi-tubes and one mold” means that tubes of the same diameter should be bent with the same bending radius as much as possible, that is, the same set of modules should be used to bend different shapes of tubes, which will help reduce the number of modules.

Bending radius

The bending radius of the catheter determines the resistance of the catheter during bending.
Generally speaking, a large pipe diameter and a small bending radius are prone to internal wrinkles and slippage during bending, and the bending quality is difficult to guarantee. Therefore, the R value of the pipe bending die is generally 2-3 times the pipe diameter.

Bending speed

The main influence of the bending forming speed on the forming quality is: too fast speed will easily cause the flattening of the curved part of the catheter, and the roundness will not meet the requirements, causing the catheter to tear or break; too slow speed will easily cause the catheter to wrinkle and The compression block is slippery, and the pipe with a large diameter is easy to form a depression of the curved part of the catheter.
For a large number of tests on these two CNC pipe benders, it is advisable to determine the bending speed of the pipe to be 20%-40% of the maximum bending speed of the machine.

Mandrel and its position

The core rod mainly plays the role of supporting the inner wall of the bending radius of the catheter to prevent its deformation during the bending process.

There are many types of core rods, such as cylindrical core rods, universal single-, double-, triple-, and four-ball head core rods, directional single- and multi-ball head core rods, etc.

In addition, the position of the mandrel also has a certain influence on the bending of the pipe: theoretically, its tangent should be flush with the tangent of the pipe bending die, but after a lot of tests, it is better to be 1~2mm ahead of time. At this time, the quality of the pipe is better. Ideal. Of course, too much advance will cause the so-called “goose head” phenomenon on the outer wall of the curved part.

Video of section and pipe bending machine