I am still building my cnc but I have been working with acrylic for years with conventional tools, a hand held router, and using a router table. I mainly work with 1/4" and 3/8" material but have worked with thickness up to 1.5". My router speed is non adjustable (24k rpm) and I use both a 1/4" width and 3/8" bits. In my expierience it does not care how slow I am going but it does start to do some weird stuff when I pick up the speed. I always try to set it up where I can make a finish pass because pretty much any interior cut is going to leave a bad edge and a finishing pass cleans it up perfectly. Also cast and extruded acrylic machine totally different. Cast has a much higher heat tolerance and will be easier to machine perfeclty without it "gumming up" all over your mill. I would suggest making several passes to cut through the material.