The benefits of screw cooling for improved solids conveying for smooth-bore, single-screw extruders

All sections of a single-screw extruder must be operating well to maintain the maximum profitability of the line. The solids conveying section must be able to operate at a rate high enough to keep the metering section full of resin and pressurized. Optimal solids conveying depends on the forwarding and retarding forces on the solid bed, and these forces depend on the barrel and screw temperatures. Usually, a considerable level of care is given to setting the barrel and feed casing temperatures. The temperature of the screw, however, is typically not controlled. Instead, the screw temperature is unknown and often hotter than optimal. Screw cooling can improve solids conveying for many processes. This paper discusses the fundamentals and operational practices for using screw cooling.