First off, a slight update. I'm working on the 3rd version printer, which should actually be able to print. Since I won an NXT 2.0 in the Toy challenge with this, I should be able to make another one for the next contest that features a Makerbot.
I originally wanted to create a lego 3D printer for the makerbot challenge, but wasn't able to finish it in time. So, since another makerbot is up for grabs, I decided to do a second version of the printer. Since I have no extruder, I can't actually have it be a 3D printer. That's why it's currently configured as a pen plotter. Also, this takes a massive number of parts. I had to scrounge around for all the little pieces I need.
This is my first instructables, so I've decided to do the guide with a combination of two different techniques. I'm using Lego digital designer to design some of the sub-builds. I've exported each sub-build as an html file and html files are each given a number. (All of which are in the "building instructions.zip" file) I'll reference them by B#. ie, B1, B2 or whatever. So when I say build 2 of B1, I mean open up 1.html and build it twice. If you have Lego Digital Designer (LDD) and would rather use it, the "models.zip" file has all of them by the same number. It's just B1 is 1.lxf instead of 1.html. Sorry if that's confusing. The second approach was to take pictures of putting the sub-builds together.
Here is a video demonstrating what it can do: