Novel multi-axis differential velocity sideways extrusion process for 3D curved profiles: Feasibility and forming mechanisms studies

Abstract

3D curved profiles or extrudates are widely used in industry; however, their flexible manufacturing with very few processing steps remains a great challenge. In this study, a novel extrusion-bending integrated process, termed multi-axis differential velocity sideways extrusion (MX-DVSE), was developed to form controlled 3D curved extrudates within a single operation, and its forming mechanics was clarified by experiments and finite element modelling. The MX-DVSE equipment was set up, and a set of dies was designed to perform a series of experiments in which two pairs of opposing punches were moved at different velocities. During the MX-DVSE process, the superposition of the velocity gradients generated by the four extrusion velocities induces the bending deformation of the extrudates with a controllable bending radius and deflection angle. The bending radius is determined by velocity gradient, velocity gradient ratio, and extrusion ratio. The bending radius decreased with an increase in the deviation of the velocity gradients from 1, reduction in the velocity gradient ratio, and increase in the extrusion ratio. The velocity gradient and velocity gradient ratio can be unified into a proposed indicator, termed the bending radius control factor, which exhibits a monotonic relationship with the bending radius. The deflection angle depends on the extrusion velocity and the velocity gradient. The bending plane of the extrudate was close to the direction of the velocity gradient, which deviated from 1 or the direction of the maximum velocity. This is reflected in another proposed indicator: the deflection angle control factor. The feasibility of the MX-DVSE technique was further verified by considering the specific shape and size of 3D curved extrudates as the forming targets. The experimental results show that MX-DVSE can form 3D curved extrudates with acceptable dimensional accuracy, and the proposed control factors for the bending radius and deflection angle can accurately control the shape of the 3D curved extrudates. Moreover, compared to forward extrusion, MX-DVSE was more effective in refining grains and enhancing the strength and ductility of extrudates with the same extrusion parameters. This study demonstrates that MX-DVSE has great potential for the development and application of flexible manufacturing of 3D curved extrudates.