Effect of Roller Angle on Formability in Rotary Forming of Spiral Corrugated Tubes

Spiral corrugated tubes are widely utilized to enhance the performance of heat exchangers. However, they are typically formed via hydroforming, which renders efficient manufacturing challenging. Therefore, this study presents a rotary forming method using multiple rollers for the continuous production of spiral corrugated tubes. During the forming process, the rollers rotate around the tube, pressing against its outer surface, and the tube moves axially, forming spiral grooves. This study experimentally evaluated the effects of varying roller angles on formability by analyzing maximum rotation speed, outside diameter, thickness distribution, groove depth, and peak pitch. The experiments were performed thrice under each condition to ensure reproducibility. The results indicate that the formable rotation speed increases by 40% when the roller angle is adjusted from 32° to 40°. For the same rotational speed, a larger roller angle prevents stress concentration. As the roller angle decreases, the outside diameter also decreases, and the groove depth and peak pitch tend to increase. Under a roller angle of 40° and a rotational speed of 150 rpm, the thickness deviation ratio of the formed product is only 0.13, demonstrating improved uniformity.