Automatic tooling design for rotary draw bending of tubes

Cold rotary draw bending of tubes is a CNC metal forming process widely used in industry. When planning a new process, trial and error is often required in order to calculate the proper overbending and to avoid wrinkling, excessive thinning and flattening. Process design is a critical, difficult, experience-based activity, that requires the selection of several variables. In this paper, a comprehensive, computer-based methodology, called Tube ProDes, is proposed for process design of the rotary draw bending of tubes. The approach can be described as follows. First, numerical calculations are carried out in order to compensate for springback, to evaluate the severity of the bend (i.e. the risk of the occurrence of defects), and to assess the sensitivity of the process to a change in the material properties. Then, the tooling setup is completely designed by fuzzy logic, using the tube material properties, the geometrical data of the bend and the variables previously calculated as input.