Here's a link to a video of my drawbot
. A drawbot seemed to me to be the simplest/cheapest/easiest entry into cnc that actually does something. It's basically just two steppers, two pulleys, some belt, and some miscellaneous stuff. The next step up in complexity is the eggbot, which we also have at Fubar.
I didn't want to look at anyone else's code for my drawbot, as I really wanted to learn how to make it move on my own, using the Accelstepper library and Adafruit motor shield on an Arduino Uno. The math is really simple, not much more than the Pythagorean Theorem. Once I got it working with some x/y coordinates, I had it draw a star:
... but it was strangely distorted. At least it looked like a star, though! I was on my way. Once I corrected the stepper speeds for the slopes of the lines I was drawing:
... I got a star that was a little better laid out. The waviness had to do with resonance in the belts and gondola, so I slowed down the motion considerably:
Success!! Still some tweaking to do to get 1" to equal 1", and square everything up, but I was on my way, with a handle on getting steppers to work, stepper drivers, acceleration, resonance, speeds, etc.
I had seen several drawbots on the web, but the one that threw me over the edge was the "polargraph":http://www.polargraph.co.uk/
.. the drawings it does are really something special. The device is so simple!