Tube bending technology is widely used across various sectors, including the boiler and pressure vessel industry, central air conditioning manufacturing, the automotive industry, aerospace, and shipbuilding. The quality of the bent tube directly impacts the structural integrity, safety, and reliability of the final products in these industries. Therefore, to produce high-quality bent tube components, it is essential to master the processing techniques applicable to different operational conditions.

When performing tube bending using a bending machine and tooling, the bending radius for cold bending should generally be no less than 1.5 times the tube diameter. Due to the inherent elasticity of the material, the tube will spring back by a certain angle once the external bending force is removed; consequently, a degree of "over-bending" is required during the process. The extent of springback depends on factors such as the material's mechanical properties, wall thickness, and the bending radius; for copper tubes, the springback angle typically ranges from 2° to 4°.

Tube bending involves clamping the tube to a bending die and rotating it along with the die. As the tube is pulled past the pressure block, the block forces the tube to wrap around the bending die—a process known as rotary draw bending. With advancements in CNC technology, utilizing advanced CNC tube bending machines (such as those from Huameng Machinery) to execute this rotary draw bending process can significantly boost production efficiency and ensure product quality. Because process parameters can be easily adjusted, CNC bending machines perform operations—such as straightening, rounding, feeding, and bending—with high accuracy and stability, thereby guaranteeing the precision of the bent components. However, the quality of bent copper tubes is particularly sensitive to process parameters, necessitating thorough preparation and trial production. This is especially critical when bending thin-walled copper tubes; improper parameter selection can easily lead to wrinkling, resulting in scrapped parts. Efficiently and accurately determining these process parameters to ensure the quality of bent pipe products is a key area of research in CNC rotary draw bending.

During the copper pipe bending process using a bending machine, the position of the mandrel relative to the bending point is critical. While positioning the mandrel ahead of the bending point (so that its working end enters the bending zone) can reduce ovality, excessive lead distance increases wall thinning; therefore, the optimal mandrel position should be finalized after bending three to four test samples. Additionally, one must account for the tendency of the mandrel to shift backward when bending thick-walled pipes and forward when bending thin-walled pipes.