Prevention of defects by optimizing mandrel position and shape in rotary draw bending of copper tube with thin wall

A series of experiments and a finite elements analysis was carried out in order to investigate an optimum condition of a mandrel for preventing defects in a rotary draw bending of a copper tube with thin wall. The mandrel position and shape, which is a diameter and a tip radius, is important for preventing the defects, such as a flattening, a wrinkle and a crack. As a result of experiments, the optimum condition of the mandrel was determined when a bending radius was two or three times of the tube diameter. In addition, a mechanism for preventing defects was considered by finite element analysis.