Hello,
I built my own cnc router, plasma cutter, mill and lathe. It is a rack and gear on the x and y axis and ball screw for the z-axis. It is a simple design using square tubing and flat steel with steel v-wheels. I built mine 72" x 72" with 10 " travel for the z-axis. You can build it to any length. I originally used 6" x 8" flat steel for the motor plates and wheel plates but I am changing them to aluminum 10: x 10" for a large machine it is more stable and aluminum is much easier to work with cutting and drilling. I used 1/4" square tubing and there is no flex and it is ridge enough to cut steel. I have been using a 2 1/2 hp router for milling but it has taken a toll on the bearings so I am changing to a 4 kw vdf spindle. My design is easily built with small tools. (drill, hack saw or chop saw and a small welder) The square tubing goes together like a bumper receiver hitch on a truck or car. If you are interested I can post pictures are there is a short youtube video
