On the minimization of the exit profile curvature in extrusion through multi-hole dies: a methodology and some verifications

In this study, a methodology has been presented for radial positioning of the die holes in multi-hole extrusion of non-symmetric sections. The objective of radial positioning is to minimize exit profile curvature. For this purpose, a two-hole die with non-symmetric T-shaped holes has been investigated. A kinematically admissible velocity field at deformation zone has been developed. The deformation region includes the dead metal zone (DMZ) which is assumed to be linear. The DMZ length was obtained by energy minimization through the upper bound method. To predict the exit profile curvature a deviation function has been suggested. Using the proposed function, the velocity field has been used for prediction of the exit profile curvature and thereby positioning of the die holes. The predictions of the proposed methodology were validated with physical modeling. With little development, this methodology could be applied to dies, which have more holes and/or generate profiles that are more complex. This will help die designers enhance the quality of extrusion process.