A novel method to reduce the distortion of ridged rectangular tube in H-typed rotary draw bending

Ridged rectangular tubes are widely utilized in microwave equipment as waveguides. However, cross-sectional deformation easily occurs when a ridged rectangular tube is bent. Especially for H-typed bending, the deformation of ridge grooves cannot be controlled effectively by using the current bending tools. Therefore, a novel method adding fillers in ridge grooves to reduce the distortion is presented in this paper. According to this method, a three-dimensional finite element model of H-typed rotary draw bending of H96 brass double-ridged rectangular tube with ridge groove fillers was established, and then the reliability of the model and new method was verified by the experiment. It is found that when fillers are used, cross-sectional deformation significantly decreases, especially the height deformation and the spacing deformation of ridge grooves. Moreover, an obvious decrease in the distortion difference between different sections is observed, which means the distribution of deformation ratios along the bending direction is more uniform. Through further validation with a single-ridged rectangular tube, it shows that the novel method is feasible and ridge groove fillers are strongly recommended to be introduced in the bending of different ridged rectangular tubes.