In the extrusion process, metal is compressed and forced to flow through a suitably shaped die to form a product with reduced but constant cross section and may be performed either hot or cold
1:the extrusion process is like squeezing toothpaste out of the tube
2:A ram advances from one end, causing the billet to first up-set, and conform to the confining chamber.
3:As the ram continues to advanced the pressure builds until the material flows plastically through the die and extrudes.
4:The stress state within the material is one of tri-axial compression