Effect of die pockets on multi-hole die extrusion

It is well known that die pocket technology if properly adopted in the extrusion process can, to some extent, balance the material flow. However, the literature describing or analysing this process is sparse although the industrial application of pocket die extrusion is quite common. In this paper, the influence of the pocket on material flow in multi-hole extrusion is modelled by three-dimensional FEM. The exit velocity profiles, the temperature difference, the deformation history of the material across the die orifice are clearly illustrated, and they correspond well with experimental data. It is shown that the material flow can be more homogeneous than normal extrusion if the appropriate pocket die design is applied. The influence of pocket die design on material structure is also studied by the use of physically based models combined with FEM simulation.