The difference between the two extrusion methods is that, in direct
extrusion, there is no relative motion between the die and container during
extrusion. In the case of indirect extrusion, however, the die fixed
on the front end of the hollow stem penetrates into the container. Thus,
in comparison with direct extrusion, indirect extrusion has advantages
in that the process reduces the extrusion pressure, increases the billet diameter,
and starts extrusion with a lower billet temperature for critical
shapes