The ingot must have reached molten temperature by the extrusion stage. However, certain adaptations must be made. When an ingot is pressed through the tool, the mechanical re-shaping forces produce a substantial increase in temperature.
In order to keep the extrusion temperature as constant as possible, the ingot must have a varied temperature. This is achieved by heating the front end of the ingot to a higher temperature, which will be compensated for by the surplus heat generated by re-shaping.
This compensation varies according to profile shape and the alloy used.
High levels of mechanical re-shaping and hard alloys result in a higher increase in temperature and therefore require greater compensation.