The new ERF melt filter series from Ettlinger North America, Chicago, reportedly can filter plastics with contamination levels up to 16%, vs. 0.5% to 1% for conventional filters. The special design features a rotating filter drum that carries the foreign particles to a scraper, which lifts up the contamination and guides it directly to a discharge screw. The ERF’s holes are drilled and thus cannot expand, unlike wire, screen, or mesh filters, the company says. Also, the ERF Filter has conical holes to prevent blocking of the filter surface. The rotating drum design is said to be well suited for filtering plastics contaminated with rubber and silicone.
The speed of the filter and discharge screw, and the pressing force of the scraper, automatically adjust to the melt pressure in front of the filter. As a result, the foreign particles make up 60% to 70% of the mass of the discharged material, reducing melt loss. For example, a typical contamination content of 5% will result in a melt loss of only 2%. The continuous cleaning action of the ERF means more consistent melt pressure in the process. Labor can be minimized with a fully automatic, continuous version.