Both heated and cool raw materials are amendable to twin screw extruder extrusion processing
Basically, the extrusion process involves loading small pieces of raw material or stock into a hopper at one end of the single screw extruder. In the case of the plastic extrusion process, this raw material is called pellets, and in the aluminum extrusion process, billets. The raw stock is fed from the hopper into the screw extruder, essentially a heated cylinder, where it is softened. A ram, usually a worm gear, forces the semi-liquid raw material through a smaller chamber, then through a shaped die. From the die, the extrusion, the string, tube, or rod of shaped stock, is cooled with water or air, along the run out table to harden. At the end of the run out table, the hardened product is cut, wound, shipped, or sent on to further refining.
Both heated and cool raw materials are amendable to twin screw extruder extrusion processing. Of course, the cooler raw material, the pellets or billets, for example, require far higher pressure to force the less malleable material through the smaller chamber and the die. The temperature and pressure factors in the extrusion process are crucial to the tempering, the strength and finish, of the end product. The extrusion ratio, the division of the cross-sectional area of the entire die by the cross-sectional area of the extruded product is also crucial in determining the best method of extrusion, cold or hot, high pressure or low pressure.
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