Introduction to pipe bending process

Introduction to pipe bending process
1: Introduction to mold design and selection

1. One tube, one mold
For a pipe, no matter how many bends there are, no matter what the bending angle is (should not be greater than 180°), the bending radius should be uniform. Since one pipe has one mold, what is the appropriate bending radius for pipes with different diameters? The minimum bending radius depends on the material properties, the bending angle, the allowable thinning on the outside of the bent pipe wall and the size of the wrinkles on the inside, as well as the ovality of the bend. Generally speaking, the minimum bending radius should not be less than 2-2.5 times the outer diameter of the pipe, and the shortest straight line segment should not be less than 1.5-2 times the outer diameter of the pipe, except for special circumstances.

2. One tube and two molds (composite mold or multi-layer mold)

For situations where one tube and one mold cannot be realized, for example, the customer’s assembly interface space is small and the pipeline layout is limited, resulting in a tube with multiple radii or a short straight line segment. In this case, when designing the elbow mold, consider double Layer mold or multi-layer mold (currently our bending equipment supports the design of up to 3-layer molds), or even multi-layer composite molds.

Double-layer or multi-layer mold: A tube has double or triple radii, as shown in the following example:

Double-layer or multi-layer composite mold: the straight section is short, which is not conducive to clamping, as shown in the following example:

3. Multiple tubes and one mold
The multi-tube mold used by our company means that tubes of the same diameter and specifications should use the same bending radius as much as possible. That is to say, the same set of molds is used to bend pipe fittings of different shapes. In this way, it is possible to compress the special process equipment to the maximum extent, reduce the manufacturing volume of bending molds, and thereby reduce production costs.
In general, using only one bending radius for pipes with the same diameter specification may not necessarily meet the assembly needs of the actual location. Therefore, 2-4 bending radii can be selected for pipes with the same diameter specifications to meet actual needs. If the bending radius is 2D (here D is the outer diameter of the pipe), then 2D, 2.5D, 3D, or 4D will suffice. Of course, the ratio of this bending radius is not fixed and should be selected according to the actual layout of the engine space, but the radius should not be selected too large. The specification of the bending radius should not be too large, otherwise the benefits of multiple tubes and one mold will be lost.
The same bending radius is used on one pipe (i.e. one pipe, one mold) and the bending radius of pipes of the same specification is standardized (multiple pipes, one mold). This is the characteristic and general trend of the current foreign bend pipe design and modeling. It is a combination of mechanization and The inevitable result of automation replacing manual labor is also the combination of design adapting to advanced processing technology and advanced processing technology promoting design.