An analytical model integrated with toolpath design for wrinkling prediction in conventional spinning

Blank wrinkling is the most frequently encountered material processing failure in spinning. Design of toolpath profiles and selection of process parameters are important in preventing wrinkling. Existing studies employ simplified toolpath profiles and rely on the calculation of maximum and critical stresses of the blank to determine the onset of wrinkling, often requiring time-consuming Finite Element simulations. To overcome these limitations, this paper develops an analytical wrinkling prediction model integrated with toolpath design in developing multi-pass conventional spinning. The toolpath design is parameterised for concave, convex and linear profiles and a wrinkling-wave function using a concave profile is developed to capture geometrical characteristics of a wrinkled blank. The forming depth is introduced as a critical variable in designing a toolpath profile to control wrinkling. Material plastic deformation is analysed by employing the Donnell-Mushtari-Vlasov theory and wrinkling initiation is predicted by the occurrence of the instability of the blank as a doubly-curved thin shell. Experimental tests of first-pass conventional spinning using concave, convex and linear toolpath profiles are performed to validate the developed wrinkling prediction model. The experimental validation confirms that the proposed critical forming depth of toolpath profile is an accurate and effective measure in predicting the onset of wrinkling. The results show the significant effect of the design of toolpath profile, blank thickness, spin ratio and feed ratio on the onset of the wrinkling. The wrinkling prediction model is capable of producing processing maps of these key parameters to prevent wrinkling for the spinning process development in practical applications.