According to resin pricing experts, plastic materials represent the single most costly element in a film and sheet extrusion operation. And while all costs have risen over the last decade, the price of film and sheet feedstock resins has skyrocketed. Polypropylene has increased from about $0.30/lb in 2000 to$0.90/lb or more today. High-impact styrene has doubled in price from around $0.55/lb in 2000 to over $1.00/lb today. The picture for polyethylene is much the same.
To stay competitive, film and sheet extruders have got to squeeze every bit of production out of their operation and do it smarter and better than the competition. Savvy processors know this and have structured their plants to achieve maximum throughput while maintaining quality and minimizing scrap. However, the real challenge lies in the fact that so many variables can affect throughput: screen-pack blockage, melt-temperature variations, screw wear and resulting leakage-flow over the flights, loss of cooling of the screw or feed throat, or changes in material behavior, including normal drifts in bulk density. As if all of these processing and ambient conditions affecting output aren’t enough, you also need to contend with the most insidious of them all: operator interference. Whether they have years of experience or are completely green, rarely will two operators run an extrusion line in quite the same way.