A machine for producing more or less continuous lengths of plastic sections.Its essential elements are a tubular barrel, usually electrically heated; a revolving screw, ram or plunger within the barrel; a hopper at one end from which the material to be extruded is fed to the screw, ram or plunger; and a die at the opposite end for shaping the extruded mass. Extruders may be divided into three general types—single screw, twin-or multiple screw, and ram—each type has several variations.