Surface flexible rolling for three-dimensional sheet metal parts

To realize highly effective and continuous fabrication of three-dimensional (3D) sheet metal parts, a new forming method, surface flexible rolling forming, has been investigated. This method takes only two integral flexible rolls as the forming tool. In the forming process, a non-uniform elongation in the rolling direction and a bending deformation in the thickness direction occur simultaneously, and finally three-dimensional surface parts are formed. In this work, the basic principle and forming mechanism of surface flexible rolling are studied. A method to calculate the transversal curvature radius of the arc-shaped roll is brought forward, while the feasibility is verified by the explicit dynamic finite element analysis. An experimental device has been developed and the forming experiments have been performed. Typical 3D surface parts including the convex and saddle surface parts have been obtained. Finite element model of surface flexible rolling is established and the effect of forming parameters such as reduction, velocity, bending radius and friction on the surface shape is analyzed. The forming effects including shape errors and thickness changes are studied by the deviation analysis. The results indicate that the formed surface is quite close to the criteria one; the thickness of the parts changes gradually and keeps within a narrow range. The experimental formed parts are measured and the forming accuracy is investigated. The results show that the accuracy is high, and are consistent with the simulation.