When I started thinking about CNC machines, I just wanted a computer-controlled machine that would be able to automatically drill all of the holes in the printed circuit boards that I made, for my Curve Tracer kits (see the link, above). But, the “good” commercially-available machines were priced higher than the amount that I could justify spending. So, I started thinking about what it would take to build one, myself. And, I didn’t want to build one that would cost almost as much as a commercial machine: Otherwise it might have been smarter to just BUY one, to begin with! So, I decided to add “low cost” as one of the design goals. I also expected to end up with one or more additional products to sell, as a result of this project, to (help) justify the time that I spent on it. Link.
Building Inexpensive CNC Machines