Actually the vast majority of milling plastics is with a router, although mostly CNC. Just turn the speed down and use plastic bits made for the purpose, mostly O-flute. There are even bits dedicated for particular types of plastics. I the past I drilled holes using various carbide hole saws, again at slow speed and clearing the bit frequently, but I use my Shaper now. Usage recommendations by manufacturers recommend routing or sanding edges especially on acrylics to reduce micro cracks that can expand later.