Update: Now that I’ve been using the mill for a bit, I’ve learned some things. Firstly, I really need to invest in real motors. The ones I’m using from the Cannon scanners get wicked hot after about 5 minutes, are very weak for their size, and inaccurate. Second, I originally wasn’t thinking when I asked for this mill. It’s fairly accurate, but the Y travel of ~1.5″ just isn’t enough to mill much besides words in metal or tiny circuit boards. Also, the Z travel makes it impossible to use with my vice, unless the tool is less that 0.5″ long. Anyhow, I’m looking for some new motors, and I’m starting plans to build a large mill this summer.
I’ve wanted to build a CNC machine for about 2 years now (since I found out what one was). Mostly I wanted one to make robot parts and such, since I always had problems machining them by hand. This year I finally had the tools available to me to fabricate the parts neccesary to convert a standard mill to CNC. I got a wicked small Proxxon MF-70 for christmas (thanks parents!), and went about the process.
My friend Ken had 3 matched unipolar stepper motors from Cannon scanners that he donated to the cause (to be fair, I agreed to make him PCBs with the mill). I first built a controller that converts steps and direction signals from the parallel port to stepper control signals. First, the direction and step signals are converted to the correct stepper high and low states for the stepper motors by 3 L297 chips from ST Micro. I really do love these drivers, and use them in pretty much any project involving a stepper. Since the logic of these chips can’t sink or source 3 amps, I use 12 TIP102 transistors (4 per motor, 1 per coil wire) to provide switching to the motors. Each motors’ common line is hooked to the +12v supply from the board, and each control line is ground-side switched by the transistor.
The only other things on the board are a giant filter capacitor (stepper motors are very spiky things), a 5v regulator, a P3 fan to cool the transistors, and some pretty LEDs to a) let me see which liens are changing in order to debug things and b) look cool. (Click on any picture for a larger view)
The whole unit is currently powered by a giant 12v lead acid battery. I guess I’ll eventually have to find a way to charge this thing or build a power supply, but I had this sitting around and didn’t feel like making a supply. I’ve used the mill quite a bit so far and it hasn’t noticably discharged.
So… here it is 
And yes, that is my bed. Note that a CNC mill in your bed makes it not very condusive to sleeping… but some things can be sacrificed.
Close up of the front:
The X-axis controller:
Y-axis:
Z-axis:
I got this sweet 2.5 horsepower 2.5 gallon shop vac. It fits right next to the spindle and moves up and down with it, so it sucks up all the aluminium, as well as cools the bit fairly well. It effectively keep aluminium off of my bed.
This is really the best thing I’ve made so far, but I hope to get time to work on some cooler projects shortly in the future.
A success!