The Problem:

Extreme Coatings was asked to contact an extrusion customer with a high wear process. This is a 6”, 32:1 screw with a barrier flight and mixer. The screw extrudes sheet of high load calcium carbonate (70%) filled polypropylene which is then formed into sound deadening panels. From 10 to 20% regrind is fed back into the process and most wear is concentrated in the feed section of the screw.

Colmonoy 83 hard facing protects the flight lands and the initial 70” of the feed section are coated with .008” of tungsten carbide. Screw life with hard facing and hard chrome was only five months in this process. The addition of carbide coating to the feed area extended life to about ten months. Total OD wear is nearly .100” and screws are removed when their output drops by 15%.

The Solution:

Extreme Coatings encapsulated the first 70” of this screw with .020” overall of our XC9000 Millennium carbide which is designed for fine particle abrasion. The screw was installed in a new carbide lined barrel and began production in October of 2005.

Benefits:

Due to a large back-log the customer never measured the screw. In February 2007, after 17 months of continuous operation, this screw was removed and a back up screw installed. The OD had wear up to .080” on some flights and minor flight side erosion was evident. The overall condition was very good, no flight thinning or root wash, and the screw can easily be rebuilt.

Most important for this processor was steady, consistent output over the life of the feed screw. Large extrusion feed screws, with a large tolerance for wear, benefit from a thicker carbide encapsulation not only with much longer wear life but at significantly lower overall cost.

Technical Specs: