Got my first CNC mechanicals and electronics done and running! Pretty fun to play with, easy to stay up late having it draw stuff with the obligatory marker pen for testing.
Some pics:
First pic is the overall design. MDF and two drawer slides make up the X axis, along with 1/4-20 rod and a 1/4-20 coupler nut for the driving nut. The nut is attached to the wood platform with two adjustable plates which allow height and side-to-side adjustment of the nut to get the best alignment.
The second picture is the Z axis, which consists of parts from an old scanner, specifically, the hardened metal rod and a piece of the original scanner with its brass bushings. The second rod is actually just an aluminum tube of the same diameter as the hardened rod. MDF end supports, and set screws to solidify the whole thing. The drive screw in the Z axis is a brass 1/4 20 nut, and it sits in a "holder" which allows it to slide back a forth a bit to account for any lead screw wobble, but does not allow the nut to turn, so it always moves the platform. No solid fixation to the platform. Gravity is used to eliminate backlash. The attatchment to the second rod (the tube) is simply a flap of aluminum behind and in front to keep the small MDF platform from rotating around the hardened metal rod. You should be able to see how it's put together somewhat.
The last picture is the obligatory marker drawings for testing using Mach2 and DesignCad3D. I'd say it works pretty well for being a machine that probably only cost me about $18 total because I got mostly scrap parts from work and from around home ! Guess it pays to work in an industry which builds electronic machinery
check out the pics
-niko