A forming method of variable-diameter tubes straightforward from sheet metals

Abstract

Variable-diameter metallic tubes are extensively used in many industrial applications. They are generally made of pre-formed raw tubes by using the existing processing methods, during which obvious non-uniformity in tube wall thickness inevitably occurs. In this work, a novel method is proposed to form variable-diameter tubes directly from sheet metals by means of the roll-stamp forming technique. A three-pass roll-stamp forming process and corresponding die blocks are designed and implemented to form a demonstrative conical tube. The finite element model of the roll-stamp forming process is established and forming quality is quantitatively evaluated. The initial blank configuration, which is the most important factor for process design, is determined by combining machine learning and multi-objective optimization. The forming experiment is performed, and the conical tube is successfully formed with no significant thinning/thickening of tube wall. The influences of forming direction and conical ratio on the forming process are numerically investigated. The proposed roll-stamp technique provides a novel and effective approach to manufacturing variable-diameter tubes.