Bending is the most commonly used bending method in the bending process. According to the different bending equipment, it can be divided into manual bending and pipe bender bending. Because manual bending does not need special bending equipment, the bending device is simple, the manufacturing cost is low, the adjustment and use are convenient, but the labor intensity is high and the productivity is low, so it is mainly used for small batch production. Bending of pipe bender can be divided into cored elbow and coreless elbow according to whether there is mandrel or not. There are many ways to process bent pipes. According to the bending forming method, it can be divided into rolling bending, pressing bending, pushing bending and winding bending.

Bending can be divided into die bending and die bending according to whether the die is used or not, and bending can be effectively divided into core bending and core bending according to whether the mandrel is used. According to whether it is heated during bending, it can be divided into cold bending and hot bending. In recent years, new bending processes such as zero radius bending, intermediate frequency induction bending, thermal stress bending and laser forming bending have also appeared.

The mandrel-type elbow is usually pushed by its horn mandrel under axial thrust, which makes the tube blank expand circumferentially and bend axially, thus pushing the tube blank with smaller diameter into an elbow with larger diameter.

In the manufacturing process, roll bending mainly uses its three rollers to bend pipes, but its roll bending has certain requirements on bending radius, which is very suitable for thick-walled pipes with large curvature radius to a certain extent, but it is powerless for small radius bending. The method and working principle of roll bending are basically the same as that of sheet metal roll bending, except that the roll used for tube roll bending has a working surface consistent with the cross-section shape of tube blank. When bending, it is only necessary to change the distance between the driving roller and the driven roller, so that bending with various curvature radii can be realized. Among them, the roller is the driving wheel and the other two are the driven wheels. This method is especially suitable for bending annular or spiral pipe fittings.

Standards and regulations for elbow processing

1. The processing of bent pipes must comply with relevant standards and regulations (bent pipes should be horizontal, flat and vertical, and the span and spacing should meet the specification requirements). No matter how high the elbow is, instability is not allowed.

2. The materials used for processing the bent pipe must pass the inspection, and it is forbidden to use bent pipe frame rods, connectors and fasteners with defects such as deformation and cracks. Fasteners and connectors of bent pipes shall not be repaired by welding.

3. The foundation ground of the elbow must be flat, dense and hard, and its metal bottom plate must be flat without deformation. When the ground is soft, you must use sweeping poles or mats to increase the stress surface and stability.

4. The springboard on the elbow must be laid neatly, with the same width and length (except for special parts). The springboard on any bend must be firmly fixed, and there should be no big holes on the platform surface (except for special parts).