One very important issue with milling plastics...make sure it is going to cut clean, meaning most plastics will melt and get stuck to the bit as well as sticking to itself. With the high speed of the CW a lot of heat is created. When ordering acrylic for lithopanes it is highly recommended to use "Cast" and not "Extruded" There is a lot of discussions about this on the forum here. I have machined (manually) using a bridgeport a lot of different materials, from lead to stainless steels and everything in between including plastics and nylons, even using lower bit speeds and coolants most plastics want to melt.
Just my 2¢ worth...good luck
CarverJerry
ver. 1.188 Win 7- 64b with 6 GB ram @ 2.8Ghz and dual 1Tb hard drives. Rock Chuck & Ringneck vacuum system hooked up to a Harbor Freight large vacuum. Center line text, conforming vectors.