Optimization of cold heading preform dies using FEM analysis and a multi-criteria Taguchi approach

The finite element simulations were used to model a three-stage cold heading process of a common bolt. Different failure criteria were employed to predict internal and external fracture of a common bolt. Cold heading preform geometries were optimized with respect to part failure and forming load using a multiple-criteria Taguchi method. ANOVA, for design factors' contribution to the overall evaluation criterion, was also presented. The bolts manufactured by this cold heading technique are sometimes rejected because of external defects. The likelihood of defects due to shear bands was found to be unaffected by changes in preform geometry and as such was not included in the optimization, which was performed considering three criteria.