Extruder, Screw Design and Size

A typical extruder for packaging applications would have a barrel diameter of 5 to 20 cm (2 to 8 in) and a length to diameter (L/D) ratio of between 16 1 and 32 1, with most falling in the 20 1 to 30 1 range. 

Extruder screws are typically built of steel alloy, and the channels may be chrome-plated to minimize scratching and other damage. The tops of the flights are often hardened with special alloys to reduce wear. 

---