Investigating the effect of moving modes of bearings on the formability of tubes during free-bending technology

Abstract

3D free-bending technology is an innovative technology in tube forming that has attracted significant attention owing to the characteristics of dieless forming and the diverse shapes of the product. The arc section of the tube was separated into controlled and uncontrolled areas based on free-bending technology. During the free-bending process, the moving mode of the bearings in controlled areas plays a significant role in the quality and accuracy of the tube. In this study, the movement of the bearings in the controlled areas was categorized into three types: uniformly accelerated, uniform, and uniformly decelerated. To study the deformation behavior of the tube under different bearings moving modes, a finite element model was developed and validated based on experimental results. Subsequently, the effect of each bearings moving mode on the deformation section was investigated based on FEM simulation. The results indicate that the ovality of the tube is minimal when the bearings uniformly decelerate in the area before the bending zone and are uniform in the area after the bending zone, compared with other modes. Furthermore, two moving modes were proposed, and bending experiments were conducted. A new moving mode, T1, was presented. The bearings movement was set as uniformly decelerated in the area before the bending zone and considered uniform in the area after the bending zone. The ovality was reduced by 1.59% compared with the conventional moving mode. Another moving mode, T3, was proposed: the bearings movement decelerated uniformly in the area before the bending zone and uniformly accelerated in the area after the bending zone. The deviation in the bending angle between the design and T3 was 1.75%, which is an effective way to achieve the design bending angle.