The answer is PET. Many of you may know of it as Ertalyte. Ertalyte was the first PET offered on the market extruded by Quadrant EPP out of Reading PA. Several other extruders are now in the game making PET more affordable. PET is now a little more expensive than Delrin. PET meets or exceeds all of Delrin's mechanical and chemical properties but the big difference is dimensional stability during machining. You can literally take a 1.0" thick 12x12 PET plate, machine .750" off of 1 side and it will stay flat. Try that with Delrin and it will turn into a Pringle potato chip! PET is great for structural, bearing and wear or FDA or USDA parts with complex features and deep cut outs. PET is extremely stable and it holds tolerance.
For more information on PET go to: http://www.cncplastics.com/PDFs/PET.pdf or call 1-800-265-7351.
For general information on plastics please visit us at: http://www.cncplastics.com/