Extrusion : In this method of forging, the metal slug is forced to pass through a die under the action of intense of hydraulic pressure. The process can be viewed as squeezing the tooth paste. From its container under the pressure.
The extrusion process is classified as :
(i) Direct or forward extrusion : In direct extrusion process, the heated metal slug [billet] is forced to pass in forward direction.
(ii) Indirect extrusion
In this type of extrusion, the plunger consists of die and as presses the heated metal slug against the back wall of the closed, the hot metal extruded back into the plunger. It requires less force for extrusion of direct process.