Influence of pushing speed on tube formability and accuracy compensation research based on free bending technology

Considering the ambiguous impact of axial pushing speed on tube formability based on free bending technology, the influence of axial pushing speed is investigated. A prediction and compensation model for increased springback angle caused by the axial pushing speed is introduced, and the bending angle compensation equation is proposed. Then, the bending parameter calculation model is modified. Firstly, tube bending experiments were conducted at 20%, 100%, 200%, and 400% of normal pushing speed. According to the experimental results, the influence of axial pushing speed on tube formability was investigated. The results showed that the push speed has a minor effect on the variations in wall thickness and ovality on the arc section of the tube, and the tube bending quality increases with decreasing axial push speed in transition sections S1 and S3. The tube accuracy results showed that as the axial pushing speed increased, so did the bending angle error between the experimental and intended. Based on the research results, the recommended axial pushing speeds are provided for high efficiency and quality of the tube. Subsequently, the effect of different axial pushing speeds on the springback angle in S1 is investigated. The results demonstrated that S1 had a negligible variation in springback angle at different axial pushing speeds, and the difference is mostly in S2. Ultimately, the bending angle compensation equation was introduced, and springback prediction model for different bending angles under various pushing speeds was established and experimentally validated. The results demonstrated a 6.34% reduction in the bending angle error between the designed and optimized.