3D Printing Lego

The Ultimate Guide to 3D Printing Lego

When it comes to 3D printing projects, the one for me that has the most superlatives attached to it is Lego. It can be the most fun. Consider that there are literally thousands of different Lego shapes out there in the world, and a huge percentage of those can be 3D printed. It’s really hard to get bored with printing Lego.

It can also be one of the most creative projects you print. Because not only are there thousands of existing Lego shapes, the possibilities for custom shapes are very nearly unlimited.

For Lego aficionados, the prospect of printing a custom piece that’s never been manufactured by Lego and using it to build a novel structure is pretty enticing.

But this project can also be one of the most frustrating, particularly if you’re trying to print all the Lego pieces needed for a particular model. Why? Because you need a LOT of Lego bricks to build even the smallest, simplest of Lego projects.

And each of those Lego bricks and pieces needs to be printed individually and then individually post-processed. Printing enough bricks for a single Lego model can take an inordinately long time. So when does it makes sense to print Lego?


Good Reasons to Print Lego


Clearly, 3D printed pieces can’t replace your current Lego collection. It would be far too costly and time consuming to print the thousands of Lego pieces most collectors generally have.

Plus Lego bricks are legendary for their near perfect tolerances (the standard brick has a variation of just 0.004 millimeters).

Any Lego piece ever manufactured in the history of the company will fit together with any other brick, and they promise that will never change. As good as 3D printing has become it still can’t hold a candle to that level of precision.

But 3D printed Lego pieces are great ways to get custom parts. You can also print pieces that you’re missing from existing sets you own instead of buying individual pieces from Lego. In that vein, you can also print vintage parts that are no longer available. This is great for older sets you want to complete.

You can also print in custom colors to either change up pieces you already own or add your own flair into your Lego creations. And there’s nothing stopping you from printing oversized Lego pieces to build larger versions of existing models.

There are lots of designs and models available already in the printosphere. You can print them directly or use them as a base to customize your own pieces. Really the only thing limiting you is your imagination. And your patience and budget.

If you’re interested in trying your hand at designing your own custom Lego bricks you’ll need to look up the requisite specifications, like standard block heights, stud placements, heights and widths for the type of custom piece you’ll be designing.

Then you’ll need access to a CAD program like Fusion 360, OpenSCAD or Tinkercad to name a few. Unless you’ve built CAD models before there is a learning curve. But once you learn the ropes you’ll be able to build any Lego piece you can dream of.

And here’s a mindblowing concept. You can create custom-designed converter pieces that allow you to join Lego with any other building toy available. The possibilities are almost too hard to wrap your mind around.


Printer Recommendations


For most parts, stock FDM printers with the typical 0.4 mm nozzle should be absolutely fine. However many Lego parts are rather small, which means the extra resolution available from an SLA printer would do an even better job. Of course with SLA you trade off color, cost and material options for precision, which may not be a tradeoff you want to make.


Material Recommendations


Since real Lego bricks are made from injection molded ABS that would be the recommended material for printing your own. That way your custom pieces and the store-bought variety will feel fairly similar, with similar resilience and hardness features.

PLA, the most popular material for 3D printers is also a good choice, though it lacks the tensile strength of ABS and can break if stepped on (and let’s be honest, who hasn’t stepped on a Lego piece before?).

Alternately you could print with PETG. This is a bit easier to print than ABS, but offers a little better performance than PLA. It’s not likely to snap on you, but the connection it makes with genuine ABS Lego parts may feel slightly different.


Slicer Recommendations


In general, standard slicer settings should work for most Lego pieces. However, every printer can be slightly different, even among the same models.

I’d recommend you start with your normal slicer settings, print a piece, and then see how it fits with genuine Lego bricks. You can start with medium quality settings using a standard 0.4 mm nozzle.

If you have any connection issues, particularly those caused by missed tolerances or low fidelity, change your slicer settings to favor higher resolution by altering the extrusion width or print speed and then try again.

This process will take some time but once you’ve found a good balance between print fidelity and print time, one that creates pieces consistent enough to fit with existing Lego bricks, you can save and reuse those slicer settings for future Lego prints.

Just remember that thinner slicer layers will increase print times. You want to find a slicer setting that creates just the resolution you need and no more to keep print times as low as possible.

You should also keep overhangs in mind. If your printer doesn’t do well with them you may need to introduce supports to be certain these troublesome features print properly.

And if you find, particularly with smaller pieces, that you’re having trouble getting them to adhere to your printer base you can introduce a brim to help stabilize the first few layers.


Time to Print


4x2 Lego Brick



To give you a sense of how long Lego pieces can take to print I ran the three models in the main image with my Prusa I3 Mk3 printer. The large Lego Han Solo frozen in carbonite took roughly an hour. It took about a half hour to print the minifig, and the standard 2 x 4 brick ran in 15 minutes.




3D printed Lego


These are just examples from my machine. Remember that every printer model has its own print speed, so use my examples as a baseline.


Post Processing


If you’re using an FDM printer you may need to clean up the underside of your Lego pieces, where they made contact with the bridging. Other than that a quicksand and/or file of the exterior faces to clean off any burrs should get your Lego into clickable condition.

If you printed a piece that required supports or brims you’ll need to snap these off and sand and/or file to remove any remaining material.

If you’re printing your Lego pieces with an SLA printer you’ll need to do the standard alcohol cleaning to remove the sticky post-print film that adheres to your model after it comes out of the resin bath along with any needed support cleanup.


What are the Biggest Challenges You’ll Face?


Printing Lego is generally a pretty simple proposition, but you will face a few challenges to keep things interesting.

Certainly, as I mentioned earlier, you’ll have some issues matching the precision of genuine Lego parts.

Depending on your printer quality, and the settings you use you’ll be closer or further away from the requisite tolerances for a perfect Lego fit. But with some trial and error, you should be able to print reasonably decent matches with existing Lego bricks from any 3D printer.

More expensive printers are more likely to nail the requisite tolerances right out of the box, but almost any printer can get a passing grade for this project.

You’ll also have some issues with details on small pieces, and Lego has a lot of small pieces. If you have an SLA printer and don’t mind the material and color limitations this places on your print, the fidelity of this print technology will remedy the problem.

With FDM printers it may require judicious use of brims and higher slicer settings to successfully print these pieces. Again, trial and error will win the day. Your initial printings will take longer but eventually, you’ll learn proper settings for different sized pieces for your specific printer.

Many of the more elaborate Lego pieces included overhangs and/or bridges. Be prepared to add supports where necessary to make certain these features print properly without distortion.



Lego Resources


You can find nearly any Lego piece you could ever want to print online. One of the best resources available is PrintABrick. They feature over 5,000 downloadable, printable Lego pieces and over 12,000 full Lego sets, with a model for every piece you’ll need to build them contained in a downloadable ZIP file. It’s a Lego printer’s nirvana.

And just for fun here are a few specific models I like that others may be interested in printing themselves.


Melted Lego Brick


Melted Lego Brick example.

This model features a standard 2 x 4 Lego brick melting into a puddle on your table. Is it silly? Heck yes. Is it awesome? I think so. It’s a fun little model to sit on your desk or use as a conversation piece.


Jumbo Minifig


Jumbo Minifig example.

This jumbo-sized, snap together minifig is a great way to show your devotion to Lego. It also makes the perfect gift for the Lego lovers in your life.




Trilego example.

This is a perfect example of the sort of custom Lego pieces available for download, and that you can create on your own. With custom Lego pieces, there’s no limit on what you can build.

These are just a tiny drop in the bucket of what’s available out there. To find more Lego models all you need to do is search “Lego” on Thingiverse, Grabcad, or YouMagine and you’ll be overwhelmed by the possibilities.


Getting Started


Getting started is easy! As long as you own a 3D printer you now know everything you need to begin printing your own Lego bricks to include in your next Lego project. Just grab a model and start printing!