Re: Which plastic?
Polyurethane would work for your ''rubber'' press plate, but would not work well for for the die. Polyurethane is pretty squishy. Maybe aluminum dies would be better, at least it's less expensive than acetal. Acetal is expensive everywhere, I buy a lot of it. The other day I bought a piece 600x600x100mm, $1100. Given that each wing rib is different, you would be better to use MDF and install some dust collection. Even a big shop vac works pretty well and is cheap compared to buying acetal or aluminum.
Jim Dawson
Sandy, Oregon, USA