One of the things I like to use my DIY CNC router for is to make PC boards using the isolation routing technique. My latest prototype is Isolation routed PCB with solder mask for an opto isolator board to be used with the HobbyCNC Pro when the user experiences “false triggers” of their limit or home switches. I don’t encourage or use shielded wiring (see my post To Shield or Not To Shield (your wiring). But when nothing else works, this opto board will solve the problem.
This time I tried the addition of a dry film solder mask. This is my first attempt after some testing to figure out the time under the UV light (30 seconds in my case). It’s not quite perfect, but it is good enough for now. Holding the artwork down against the board with some glass will help, and having a black background below the board seems to help too.