Redesign boosts 'screwless' extruder output.

Rotary screwless extruders from InstaMelt Systems Inc. now employ auger feeding for increased throughputs. The redesign has boosted rates by 25% over the second-generation series introduced last year, according to Roy Serpa, president of the Midland, Texas, company.

He said auger feeding allows InstaMelt to offer a smaller unit for the same output rate. For example, an InstaMelt model that was comparable in output to a standard 4.5-in., single-screw extruder a year ago would now have the capacity of a 6-in. single-screw machine. Rates for the smallest InstaMelt TUP extruder now fall between 25 and 200 lb/hr. The largest unit now puts out between 3000 and 4000 lb/hr.

Serpa says the InstaMelt extruders still reduce residence time by 25%, cut energy costs by up to 30%, and have a smaller "footprint" when compared with conventional extruders. In place of the traditional screw and barrel, the Instamelt extruders employ a smooth drum, which rotates on an off-center axis inside a grooved chamber. The extruder melts the resin and pumps it under pressure through an exit port at the top of the unit. The melt then runs through a manifold to a gear pump to boost pressure just ahead of the die.

Applications for the screwless extruder include blown film and sheet as well as pelletizing post-consumer recycled flake, compounding, and alloying. (CIRCLE 7)