An Investigation on Square Tube Forming using a Reuleaux triangle

Currently the standard for forming tube is to use a variety of shaped mandrels and hydrostatic pressures. Tube forming is the expansion of a circular cross-sectional area into a variety of different shapes. This paper is focused on square tube forming. Traditionally to create a tube with a square cross-section area, a square mandrel must pass through the circular tube in small increments until the circular cross-sectional is completely transformed into a square cross-section. A novel process named Reuleaux forming to flare the tube in to a square section is introduced and the results were compared with conventional forming. In this new process, a triangular shaped bit flares circular cross-sectional tubes to square tube. While experimenting with the Reuleaux triangular bit, the force required to form the tube, profile generated and thickness distribution were analyzed. Furthermore, the effect of friction and punch speed on deformation was studied. It was found that much lower forces were required to form the shape using the Reuleaux triangle as compared to conventional forming. It was also observed that the friction and speed does not affect much during the new process.