This is a project I have been working on for the past year, it prints in hot glue and is made almost completely out of legos. Its design is roughly based on the first version of the makerbot. While it does print, I would call this more of a prototype or concept than a finished project. I am using 4 power supplies (3v extruder motor, 7.2v for nxt, 12v fan, and 115v for hot glue gun) and having to manually turn the extruder on and off, (although I am working on that one) . Unfortunately, due to my lack of programming skills, every move has to be manually programmed from the NXT programming software, I have yet to find a g-code interpreter for the NXT.
Hopefully in the next version I will be able to shorten the height of the platform, reduce wobble, and use g-code files.
But in the meantime, I have included a Lego Digital Designer file of the full printer, just about all the technic parts are exactly the same as in my printer, but for the structure I used different part placements to speed the digital building process, the structure and dimensions are still the same. under each X and Y axis there are 2 suspended blocks that I placed coins in to balance the weight of the motor on each side, for the extruder motor I used a lens adjustment motor out of an old VHS camera because it was low speed/high torque. In the .ldd file, the green box on the right side of the extruder gears is the case I made for it, it works perfectly.
While hot-glue works, its very rubbery and doesn't have many practical uses, if only one or 2 layers are printed then it will stick to glass to make window stickers, but its not sturdy or rigid, I will be experimenting with printing using wax and heat-melting resins in the future. I am currently limited to what I can make with what I have on hand, some more printed parts could really improve accuracy on this. I initially did not have enough gear racks so I asked someone who had a 3D printer at work if he could help me out, I was able to get around 30 of them printed, and while they work, they do not connect perfectly to the legos, which is what causes most of the wobble in the platform.
If you liked this and want to see more, please vote for it in the 3d printing and lego contests!
UPDATE: My project is now on Technewsdaily and Gizmag! Thank you Randal Marsh and Elizabeth Palermo for writing those excellent articles! also on Hackaday, Dvice, and many more!