Here is a way to make a computer controlled milling machine. That puts the real power of a computer control machining into the hands of the average human. Small enough to set on the desk but scalable to any size. As inexpensive as possible without sacraficing accuracy (too much). All most all the parts can be purchased in local retail stores. And above all CHEAP you can be up and running for well under $200. With it you can do 2 Dimentional engraving and PC board etching and 3D milling and modeling in Foam, Wood, Plastic and other soft materials.
Also try watching the YouTube movie at the end (the last frame).
New information on the Motor Driver Circuit is (HERE