Single Screw Extruders Hardware

The most important system characteristic determined by screw diameter is machine throughput, the amount of material that can be processed per unit time (pounds per hour, kilograms per hour). Because the extruder holds an amount of polymer equal to the volume of free space between the screw and the barrel, the throughput of an extruder is proportional to the screw diameter cubed. So, while a 2-inch extruder may process 100 lb/ hr of polyethylene, an 8-inch extruder may process 6400 lb/hr of the same material. 

Single screw extruders essentially consist of five components  

FIGURE 14-6 Schematic diagram of the feed system for a single screw extruder. 

The screw/barrel system is the heart of the operation. Not only does it pump the polymer through the die, but it must also ensure that the melt is homogeneous and has a uniform temperature and pressure. Any compositional inhomogeneities or fluctuations in temperature or pressure lead to variations in the final product. 

Feed Channel Depth Metering Channel Depth 

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In this chapter, the hardware components of a typical single screw extruder will be described. Each major component will be discussed with respect to its major function, the possible design alternatives, and how important the component is to the proper functioning of the extruder. 

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