A methodology for positioning of holes in extrusion with multi-hole flat-faced dies to minimize exit profiles distortion

In the extrusion of sections with a multi-hole flat-faced die, the proper positioning of the die holes is of critical importance in avoiding the appearance of geometrical defects. In this paper, a methodology has been presented for radial positioning of the die holes in multi-hole extrusion process. A die with two non-symmetric T-shaped holes has been chosen as the computational example. A kinematically admissible velocity field at deformation zone has been obtained. The effects of dead metal zone formation have been considered in prediction of the velocity field. To measure 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 accordingly positioning of the die holes. It was found that a balanced metal flow at the exit of extrusion die could be achieved if the position of holes is near the centroid of the die area. In order to validate the results, finite element simulation has been used. The proposed methodology can be extended to dies with greater number of holes and more complex shapes. This methodology helps the die designer to have a better quality extrusion process.