Branched tubing is an important component of piping systems. Welding structure type branched tubing has the disadvantages of low productivity and low flexibility due to difficulty in automatic welding, low reliability and low quality assurance. In this study, a new incremental burring process for manufacturing branched tubing without welding is developed to enhance the formability, product quality and process flexibility of large branched tubing. A crucial process history using a bar tool is proposed and is based on the forming characteristics of conventional forming processes, the rigid plug pull-out and T-drill methods. The effectiveness and merit of the proposed incremental burring process history is confirmed through an experiment using A5083-O aluminum alloy tube of 100mm in diameter and 1.0mm in thickness. The experimental results imply that the new incremental burring process is suitable for achieving a better wall thickness distribution of branched parts, and that a bar tool is superior to a roller tool for roundness and a wide range of applicable tube sizes.
