Another multi-screw device has grown much bigger since it was first introduced at K'98. The so-called ring extruder from 3+ Extruder GmbH in Germany (represented by Century Extruders, Traverse City, Mich.) has a circle of 12 screws, each originally of 1.125-in. diam. Since then, the company has sold units with screws of up to 4.7-in. diam. and is designing a lab model of 0.75 in. The biggest model runs at a recycling plant in Germany.
Twin-screws for foam
Some equipment makers are touting twin-screw extruders as more efficient ways to compound and extrude foamed PS board and foamed PE film. Leistritz AG (U.S. office in Edison, N.J.) modifies a twin-screw to foam and cool in one extruder by installing a high-pressure injection pump to inject liquid or gas into the barrel.
Berstorff (U.S. office in Florence, Ky.) has also modified a twin-screw extruder to foam and cool in one unit by using low-energy pumping elements that add less heat. Berstorff also combines a twin-screw compounder with a single-screw cooling extruder in its new Schaumtandex ZE/KE system, boosting output of PS foam board from 1700 lb/hr with conventional tandem single-screws to 3000 lb/hr with a twin/single combo.
More twin-screw news
Coperion (U.S. headquarters in Ramsey, N.J.), the new firm that combines Werner & Pfleiderer and Buss, will show two new developments. Coperion W&P will unveil a higher output twin-screw extruder, while Coperion Buss shows what's said to be a cost-effective kneader with higher output.
Davis-Standard Corp. in Pawcatuck, Conn., has developed a new screw geometry for the pumping zone of a corotating twin-screw for in-line compounding and extrusion. The new geometry is said to improve pressure stability by increasing leakage flow, reducing the effect of resin variations and improving quality.
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|Author:||Schut, Jan H.|
|Date:||Sep 1, 2001|
|Previous Article:||RIM & Urethanes.|