Development of bending of AISI 304L micro-tubes with micro-wire mandrel and investigation of its effective parameters

Abstract In this paper, a novel method for bending micro-tubes at room temperature has been developed. For this purpose, a bending apparatus has been designed and manufactured to bend micro-tubes under micro-wire mandrel, then, the effect of the new bending method at bending ratios of 1–3.2 and bending angles of 45° to 135° in that apparatus has been investigated. The bending of the micro-tube without mandrel and also by using a micro-wire mandrel has been evaluated and analyzed in order to compare and show the efficiency of the proposed method. For the bending process, micro-tubes of AISI 304 L with a diameter of 1250 μm have been selected. In bending operations, several parameters such as thickening, thinning, and cross-section distortion has been simultaneously investigated at different bending ratios (R/D) and different bending angles. The results of this study illustrate that the micro-tube which is bent with a bending ratio of 1, has been remained without wrinkling and rupture and the micro-wire mandrel, significantly reduces defects at critical bending ratios, it also reduces cross-section distortion by half at the bending ratios of 2 and above.