Experimental study on cross-section distortion of thin-walled rectangular 3A21 aluminium alloy tube by rotary draw bending

The cross-section distortion is inevitably produced in rotary draw bending process of thin-walled rectangular 3A21 aluminium alloy tube, which severely affects the forming quality of the tube. To predict and control cross-section distortion, the experiments with different process parameters are carried out. It is indicated that the effects of bending angle, core number and clearance between the pressure die and tube on the cross-section distortion are significant, but the effects of clearance between wiper die and tube and the boost velocity of the pressure die can be neglected. The maximum cross-section distortion is produced in the section of the angle 50°, and the position does not change with the variation of the process parameters. The results are of significance in the determination of the process parameters for the rotary draw bending process of rectangular tube.