Picture of LEGObot 3D Printer
   Ever since I saw the first makerbot, I have been obsessed with 3D printing, I am an engineering student and I don't have an extra $800-$2500, and have been doing my best to create one out of what I have on hand. I tried using arduino with easy drivers, and parallel port, but neither one gave results, I always needed a tool or part that I couldn't get.  So I pulled out my old box of legos and started building.

   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!

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What if it runs out of glue while printing? As far as I know, these glue sticks runs out very quickly( Well, for my glue gun)
matstermind (author)  andytangtsk3 days ago

Ideally, each layer is as thin as possible, so the extrusion rate is set very low, but the size of the object is still limited by the amount of hot glue stored in the extruder. However, The extruder is designed so that it can be expanded to hold more hot glue.

turtleson1 month ago
Damn, nice job, man!
matstermind (author)  turtleson1 month ago

Thanks, i am still slowly working on version 2.

yomanurock5 months ago

how do I put together all the 'non-lego' pieces? I have the lego structure and now i need to put together all the non'lego pieces.

matstermind (author)  yomanurock5 months ago

reply is above. If you can, it would be nice to see pictures of your progress.

matstermind (author) 5 months ago

There are only two non Lego pieces, the motor for the extruder (which actually could be an old rcx motor or power fuctions motor, and the hot glue gun for the extruder. the hot glue gun needs to be taken apart and have the metal heater placed in the lego "jail" to hold it together. I took the printer apart a few months ago so i can't take any new pictures. but these three best depict the placement.

MasterChick5 months ago
Oh my… You made that?
spaktashabit6 months ago

could you use something like weed wacker line instead of hot glue sticks

someone_6787 months ago
How does the hot glue come out and how do u make the extruder
matstermind (author)  someone_6787 months ago

The extruder is simply a hot glue gun with the plastic case and trigger assembly removed. A motor turns gears which pushes down on the back end of a gluestick and forces the glue out the front.

aneeshdua7 months ago

well pls tell me the approximate cost of this project....Thanx

matstermind (author)  aneeshdua7 months ago

I already had all the parts I needed, so I spent a total of $0 on it. I have no idea how much it would cost to purchase the parts new.

ManutoBck7 months ago

Sorry for be wearisome, but i relley need your help, anybody know how to put all the non-lego pieces??... I have all the Lego strucutre, but now, i don't know how to put the extruder and the non-lego pieces! Really thanks to sombody that can helps me... =)

jhardenberg7 months ago
Dude, this is a very nice job! simple programming for the NXT I think, but yes it is very nice. Now, you are an engineer! :)
matstermind (author)  jhardenberg7 months ago
ManutoBck7 months ago
First of all, sorry for my English, i'm Spanish... Second, i like to say, that this project is AWSOME! I'm trying to build for a High School project and i need some help. I have all the structure and the Lego mechanisms,but i don't know how you put the extruder, and all the non-lego pieces... I really need your help... Thanks! =)
Wow, I know nothin about programming and I want to ask you, how can you program a 3d object using a small box with 4 buttons on it???
matstermind (author)  I love pyrotechnics8 months ago
I would need to know more than "small box with 4 buttons on it" and anything in existence is a 3d object. So I would need a little more to go on. Try restating it again, an example of one that could be answered is. "Wow, I know nothin about programming, and I want to ask you, how can you program an arduino to be the controller board for a 3d printer?" then I would answer "The best option I have seen is grbl, it converts gcode into the motions needed for 3d printing" But i need something more specific.
no, i mean the NXT, how can you use it to program
matstermind (author)  I love pyrotechnics8 months ago
right now i can't. i need to use the programming software that came with the nxt to make it print. i.e.

Step 1. Motor A forward 2 rotations
Step 1. Motor B forward 2 rotations
Step 1. Motor A back 2 rotations
Step 1. Motor B back 2 rotations
etc. draws a square
Infinnion8 months ago
Wow this is amazing, just what I was looking for. I'm also a student and very interested in 3d printing for some years now (I used to have this profile for back in the day when building knex guns). Just like you, I don't have a lot of fundings but I do have a few boxes of old lego's including the older lego mindstorms. This is a great starting point and I think I'll be building it the next few weeks. Maybe it would be an idea using the lightsensor and a coloured building plate for more precession? I'm gonna try making it work with plastics so I can start printing my own aquaponics kit's!
matstermind (author)  Infinnion8 months ago
Thanks, I also started using instructables for knex guns. I don't know if a light sensor would be better, but good luck!
ty, I redesigned my concept and I think it will use a system like your's with touch sensors, how precise is your printer in mm?
(I don't know if your's uses touch sensor sry, I got that from this design:
matstermind (author)  Infinnion8 months ago
(removed by author or community request)
matstermind (author)  matstermind8 months ago
It does use touch sensors, but I didn't have enough NXT sensors so I soldered some unofficial ones together.
matstermind (author)  Infinnion8 months ago
because the movement has to be programmed manually, it would be as precise as you can calculate it. if i remember correctly, i just had it draw a 2 rotation per direction square.
Infinnion8 months ago
I don't have enough gear racks too, but I heard of a 3d shop nearby printing everything : ]
Xelrael9 months ago
could you post some detailed pics of the top unit with the gearbox?
matstermind (author)  Xelrael9 months ago
sure, which part specifically do you want?
that thread connections, which are moving the upper part and that gearbox nearby the motor...
gmailn9 months ago
is there anyway to get all the parts? Im having trouble getting them
matstermind (author)  gmailn9 months ago
Do you mean you have trouble getting the physical lego bricks, or you are having trouble getting part of the instructions to download?
The physical lego bricks
matstermind (author)  gmailn9 months ago
This project uses legos that i have collected from various sources for over a decade. keep an eye out at garage sales and thrift stores, but if you want to spend a lot of money, then you can purchase each brick individually at
I tried that site, they Don't have all the Legos
matstermind (author)  gmailn9 months ago
check ebay, which parts are missing?
the gears, the cables, the PLATE 4X6 26 DEGREES, TECHNIC 11M and 15M BEAM, CROSS AXLE, EXTENSION M/3 RIBS, the worm, and the toothed bar.
matstermind (author)  gmailn9 months ago
if money isn't a problem, then check this site, they appear to sell most types of legos
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