Rib Folding Defect Prediction of Spin-Extrusion Forming Processing of Thin-Walled Cylindrical Rings With External Cross Ribs

Abstract Spin-extrusion forming (SEF) is an innovative method for manufacturing thin-walled cylindrical rings with external cross ribs (TCRECR). The meshing motion between the feeding roll and the component shapes the rib, while the feed motion of the feeding roll causes the rib height to grow. The contour design of the feeding roll is critical, as an unsuitable design will produce motion interference, resulting in rib folding problems. This article proposes two evaluation indices to characterize the rib folding defects, one is the rib aspect ratio and the other is the relative error between the feeding roll profile's and the component profile's enclosed areas. Based on the reverse envelope motion experiments, mathematical models for evaluation indices are established, and the forming boundaries of SEF processing are determined through finite element (FE) simulations. Thus, a semianalytic model for rib defect prediction is obtained, and its effectiveness is verified based on current experimental platforms. Furthermore, the plastic flow during SEF processing is analyzed, and the mechanism of external rib folding is systematically studied. When the relative area error exceeds a certain threshold, research indicates two causes for rib folding defects. One reason is that the growth rate on both sides of the rib will be greater than that in the middle due to an increase in the squeezing force of the feeding roll on both sides. Another reason is that the motion interference between the component and the feeding roll intensifies, and the material surrounding the center folds from both sides.