3D Printing Custom Lego Pieces

I’ve previously written about how there seem to be quite a few “missing” Technic pieces. That entire article can be summed up in one image:


A few of these pieces can be obtained by clever cutting or drilling of existing pieces, but for the most part, your best option for getting them is 3D printing. I even made a video all about it. Here’s the summary: To make custom pieces like this, you need to design them with a 3D modeling program (I used Sketchup.) Then, you need to print your model with a 3D printer. I used a service called Shapeways. Here are the pieces I got back:

full set 3d prints

The first thing I noticed was how chalky the pieces were. I was definitely expecting a smoother finish.This means they get dirty quite easily.

dirty matte finish

This also results in particles flaking off when inserting pins and axles.

chalkyOnly my white pieces were unpolished – my colored and polished ones have a smoother finish – but they still flake a bit as well.not as chalky

This mostly happens on the very first pin or axle insertion – the printing process is not perfect, so the printing material sometimes fills in spaces where it shouldn’t be. Inserting a pin or axle will clear it out. However, subsequent insertions will still flake off just a tiny bit more powder each time – which means axle holes loosen their grip over time. This is unfortunate, but it hasn’t been a big problem for me yet.

The pinholes I’ve designed have a much tighter grip, due to the matte finish and a slightly-too-small design.  Unfortunately, this makes unhindered “frictionless” rotation impossible, so they’re useful as structural pieces only – not good for holding gears or other moving parts.

structural   bad cinnections

I’m happiest with how the 32-tooth gear turned out. I tried a few different designs before I got it right – the middle gear in this photo is the best version – the others use either too much or too little material.32 tooth gears

This gear is a near-perfect fit with all other gears. Under some circumstances, it is still a bit too tight, but I think that has more to do with how it is printed, not with the model design itself. This isn’t too surprising – tolerances on real Lego pieces can be as small as 2 micrometers.

32 tooth in context

Despite all of these issues, I’m still thrilled with how the pieces turned out. Here’s a studless transverse subtractor which works perfectly with my pieces:


Without my pieces, the model must be built with a litany of extra gears – adding unnecessary weight, size, friction, and backlash.


Other designs are simply impossible without these custom pieces.

You can buy any of these pieces at Shapeways, (with no markup!) or you can download my models from here to modify and/or print them yourself. I’ve put it all into the public domain. I hope that my experiences with 3D modeling and printing custom “Lego” will inspire others to continue my work — for example, correctly modeling the 28-tooth double bevel gear is far beyond my capabilities, so I hope somebody does it!

Edit: It seems someone has already made it, along with dozens of other pieces. I guess I’m not the only one doing this!

28 tooth doubkle bevel gear

Really, though, my ultimate goal is to build up enough interest and demand so that The Lego Group will take notice, and decide to produce some of these as real pieces. I find the 3D printed stuff to be quite impressive, but it still can’t compete with the real thing – which makes me appreciate the design of true Lego all that much more. So, Lego Group, if you’re listening, just know that I’m not the only Technic builder who would be thrilled to have these.

Stay tuned, because I’ve sent a few of these pieces over to the very talented Pawel “Sariel” Kmiec, who will do a full video review with his thoughts.

Thanks for reading, and please leave your thoughts in the comments below. Have I gone too far? Do you want any of these pieces? Have you printed any for yourself? Let us know!


4 thoughts on “3D Printing Custom Lego Pieces

  1. This is great! Thanks for sharing your models. I am in the process of modifying and 3D printing gears I wish Lego made too. I will have to publish my designs as well–I just finished modeling the 20 tooth beveled gear today. I get the benefit of a 2-hour turnaround on the 3D printing at school where I am studying architecture. We just acquired a Formlabs resin printer that does an amazing job producing finely detailed, strong parts. The goal of all this is a Lego six-axis robot that we hope to control with software for full size industrial robots.

  2. Pingback: 3D Printed Lego AT-AT Walks! - Charles Bartlett .net

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