I made a mini CNC laser engraver out of two old DVD drivers and use my RPi to control it. I didn't use any external stepper motor controller or existing CNC programs (I did use integrated H bridges though). The total cost of the project (excluding the Pi) is <$10.
The laser engraver is very similar to people have done before with Arduino but the control system is different. I wrote my own python code to interpret G code and control two stepper motor simultaneously. So far the engraver works perfectly. The resolution without any external driver is 0.075mm/step or 338 dpi.
here is one example
The python code can be downloaded from herehttp://hostcode.sourceforge.net/p/raspb ... r-engraver
Feel free to download, use and modify the code.
For a detailed instruction on how to build the engraver and run the code, please visit my blog post http://funofdiy.blogspot.com/2013/10/a- ... laser.html