I made this for my brother so he could have sensors or equipment navigate over a microwell plate http://en.wikipedia.org/wiki/Microtiter_plate it might not be all that useful to anyone else but still I might as well put it up here if anyone is interested. I added the sketchup model for any parts that I missed on the stl files so just use that to extract parts. I’m not going in to a full assembly description but for more details you can have a look at this post over at LMR. It also has a video. http://letsmakerobots.com/node/31381UPDATE: Just now I got some information on the 28BYJ-48 steppers that I used and can verify that this is a problem. So for anyone trying to build a sub-mm accuracy XY table, please try finding other stepper motors. This is the information I’m talking about; http://arduino.cc/forum/index.php/topic,71964.0.html