From Team 449 Wiki
Delrin is a building material also known as polyoxymethylene. It is a plastic polymer that has qualities similar to aluminum. Delrin is very stable, stiff, and gives low friction. Because of this delrin can be used in place of metal/aluminum or as a covering.
Operation and Use
Delrin can often be used in place of aluminum or other metals for low-to-moderate load applications due to its high strength (for a plastic). In most cases, Delrin is used so that something can slide across the face of the robot without metal-to-metal contact, as it has a very low coefficient of friction. Delrin should be used in any place where field elements, the mechanisms or other robots are expected to slide along the metal of the robot.
Delrin can be attached to aluminum bars through riveting or bolts. Riveting will give a good flat surface if done correctly whereas with using bolts, precise drilling and spacing have to be done. If something is sliding along the top of the Delrin, make sure it is flat with no bolt heads coming out.