Extruder, Two Stage

A two-stage extruder is used to remove air, moisture and other volatile matter after material has been melted and before it is discharged from the front of the machine. This is usually accomplished by providing an opening in the barrel directly under a deep channel vent section in the screw. The second metering section is normally made with the channel depth greater than that of the metering section to allow the vent section to operate at zero pressure.