Excessive arcs, compound bends and arcs larger than 180° should be avoided when designing and arranging pipes. Excessive arc not only makes the tooling bulky, but also greatly hinders mechanized and automated production, making it difficult for operators to get rid of heavy manual labor; arcs larger than 180° will make it difficult for the pipe bender to unload the mold.Table 1

Table 1: Fitting Angle Affects Operation

2. Standardized bending radius

The bending radius should be as far as possible to achieve "one tube one mold" and "multiple tubes one mold". For a pipe, no matter how many elbows and bending angles it has, because its bending radius is only one, the pipe bender does not change the module during the bending process, that is, "one pipe, one mold". And "multiple tubes and one mold" means that the pipes of the same diameter use the same bending radius, that is, the same set of modules is used to bend the pipes of different shapes, thereby reducing the number of modules.Table 2

Table 2: The influence of pipe diameter and bending half a catty on the mold

3. Appropriate bending radius value

The size of the bending radius of the catheter determines the resistance that the catheter is subjected to when it is bent and formed. Generally speaking, when the pipe diameter is large and the bending radius is small, the phenomenon of internal wrinkling and slippage is easy to occur 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.

4. Moderate bending speed

The main influence of the bending forming speed on the forming quality is as follows: the speed is too fast, it is easy to cause the flattening of the curved part of the catheter, and the roundness cannot meet the requirements, resulting in the rupture of the catheter. If the speed is too slow, it is easy to cause wrinkling and slippage of the catheter, and the pipe with large diameter is easy to form the sag of the curved part of the catheter. In view of a large number of tests on these two CNC pipe bending machines, it is appropriate to determine the bending speed of the conduit as 20%--40% of the maximum bending speed of the machine.

5. Appropriate mandrel and its position

The mandrel mainly plays the role of supporting the inner wall of the bending radius of the catheter to prevent its deformation during the bending process. If the pipe is bent and formed on the machine tool without the use of a mandrel, its quality is difficult to guarantee. Figure 1

Figure 1：Elbow wrinkled

There are many types of mandrels, such as cylindrical mandrels, universal single, double, three, and four ball head mandrels, directional single and multi-ball head mandrels, etc. In addition, the position of the mandrel also has a certain influence on the bending and forming of the catheter: in theory, its tangent should be flush with the tangent of the bending die, but after a lot of experiments, it has been proved that if the quality of the bend is good, it needs to be 1-2 mm in advance. If the advance is too large, the so-called "goose head" phenomenon will appear on the outer wall of the curved part.