EXTRUSION: ‘Next-Generation’ Cast Stretch Film Lines

Seven-layer line has six extruders, two operator workstations, scrap refeed.

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At an open house in May, Italian machine builder Amut Dolci Bielloni showcased new developments in cast stretch film that it says represent “a sweeping change” in the technology. At the company’s plant in Novara, Amut unveiled a concept seven-layer line equipped with six extruders. It is available in two configurations; 79 and 118 in. wide, in throughputs of 3306 and 5291 lb/hr, respectively. During the open house, the line ran at speeds of 2460 ft/min.

The extruders on the new line are equipped with water-cooled motors and gearboxes with forced-circulation oil cooling. The extruders a feature a longer-than-normal (40:1 L/D) screw, which is said to increase homogenization and output. The extruders/screen changers are mounted parallel to each other. This provides space savings and also makes maintenance and screen changes easier.

Downstream, an oversized cooling unit is designed to accommodate higher outputs. A high-speed winder offers inline slitting of jumbo rolls and runs at up to 2625 ft/min. The path from the chill roll to the winder is short to facilitate startup.

The compact line requires less than 400 ft² of space. Scrap is recovered by introducing the fluff on one side of the extruder through a “cold” system, without any contamination. Special filtering provides dust-free fluff collection. During startup, the fluff is stored in a dedicated silo, and then recovered in-line during the process.

The line also is equipped with a double workstation with touchscreen controls. That way, the operator can work in the chill roll area or near the winder. All the parameters to be checked are indicated on the display of both workstations.