Extrusion pressure = extrusion force /cross sectional area
• The rapid rise in pressure during initial ram travel
is due to the initial compression of the billet to fill
the extrusion container.
• For direct extrusion, the metal begins to flow
through the die at the maximum pressure, the
breakthrough pressure.
• As the billet extrudes through the die the pressure
………………..as the billet is becoming shorter so
the area where the friction occurs is………………
• At the end of the stroke, the pressure rises up
rapidly and it is usual to stop the ram travel so as to
leave a small discard in the container.
• Indirect extrusion, slight…………… in pressure because the work done on the billet
is converted to heat, which will gradually increases the temperature of the billet,
lowering the flow stress of the material
• At the end, the pressure increases sharply because the billet is now so short that
flow is inhibited