Lego is the best!

I wanted to know if a cheap FDM printer could produce usable Lego style bricks. I looked at a lot of the available brick designs… Some are perfect replicas of the lego designs, but they don't print so well. Some have small modifications but don't quite work right, at least on my printer. So rather than remix any of those, I created these from scratch, modelled as closely to the modern official design(1, 2) as I could make them, with some changes to aid printability, longevity of the printed blocks, proper connectivity between blocks, and compatibility with original Lego blocks. It may turn out that the small adjustments to make them work on my printer (which I believe to be very well calibrated) need tweaking to work on other printers, but my hope is I can get to a design with small adjustments to deal with FDM printing, rather than accomodate any specific printer. I.e. these stl files can be taken and with some slicer configuration produce working blocks.

Here are the first blocks that I have completed. For now, this is common standard blocks and plates, tiles and baseplates in common sizes, plus some snot (4,7). I wanted to provide all the blocks required to make a lego ball(5,8). And I plan to try to reproduce some of my favourite sets(6) from childhood (though there are some more challenging, to print and to draw, bricks in those). I will update as I add more blocks. I've added a 3mf file with my settings for review, and I'll add 3mf files for any models I have done a complete set of bricks for (mainly you can easily load the pieces needed, but also with any slicer setting tweaks required).

Requests for specific blocks welcome. Feedback about printability, connectability, etc also wanted. If you want to make some other blocks, or you find you need to tweak some tolerances to make them work for you I'm happy to provide the CAD (onshape) project, but would prefer working out what the issues are and trying to find adjustments that work for everyone (though that may turn out to be not possible).

Differences to the true design: No full draft angle on the block sides (I can find no specs on this anyway, and only note from measurement that there is approximately a 0.01mm draft on the pieces, mostly for manufacturing, so I've left that out.); No sidebars, this block design is a hybrid then with the modern design and the 80s “full wall” version(3), the sidebars would be very prone to wearing off printed in PLA anyway; No “hollow” studs, I don't think these serve any building purpose, only for manufacturing where they maintain the injection thickness and (I think) hide the ejection pin marks; Filleted the top of the stud, this is not seen in the specifications, however is evident in actual pieces (physical limits of the die machining no doubt), a small fillet aids insertion of the stud; Added “ribs” between the tubes and the walls, this is mostly to help printing, particularly the first layer (avoids hundreds of tiny disconnected circles that become disconnected columns, unsupported until almost the full block height - not a high probability of success), but also aids connectivity tightness, and the stiffness of the block walls; Added “chamfer” (about 0.1mm, up most of the side, basically a partial draft) on the bottom corner to overcome any tension put on a series of bricks places side by side (that was tending to warp the underneath tile slightly, probably due to slight elephants foot that is very hard to completely eliminate)

Adjustments: I've found I need slight adjustment to the hole the stud inserts into (about 0.1mm smaller) and also to the stud itself (about 0.1mm larger), both for tightness of fit, and compatibility with original Lego(*); the interior height of plates is also increased (about 0.2mm) to accommodate the “Lego” logo on original bricks, which is 0.3mm by measurement, but not mentioned in any specifications. All blocks (or plates) have these adjustments. I also foresee needing custom adjustment for specific blocks, for printability and for getting them to connect.

Printing: You need to be pretty well calibrated for the blocks to work properly (though as you can see from the photos, doesn't need to be perfect), particularly for connecting with original Lego. Printing with 0.4mm nozzle at 0.2mm layer height seems fine. The first layers are tricky, I tightened up my z-offset a little more, and slowed right down for the first layer (down to 20mm/s from usually 60mm/s). There should be no need for any supports, except for snot blocks - support the side studs but prevent support generation under the block. Except for anything mentioned above, there are no chamfers or fillets on the blocks (as there are none in the original design) so you need to have no visible elephants foot and need to not overshoot corners (eg good linear advance). I recommend wall ordering to print the outside first (inner/outer/inner on orca) to get better dimensionality, particularly if your studs are coming out too big, or you are blowing out the corners. I like the clean look of 1 wall on top layer. I've been printing these with 100% infill, for stability, and to avoid weird layers under the studs. Check carefully that the bridging for the underside looks correct in the slicer (an orca bug caused mine to fail before I turned off "detect overhang walls"). I tried with ironing on and they look great, however have not used it much as I kept having failures trying to iron 25 tiny studs - which was just chewing out the filament too much with all the retractions and micro extrusions then getting it jammed in the bowden tube.

(* It's possible others will need different adjustments here depending on the calibration of your printer)

References:

1. [https://orionrobots.co.uk/wiki/lego_specifications.html](https://orionrobots.co.uk/wiki/lego_specifications.html)
2. [http://www.bartneck.de/2019/04/21/lego-brick-dimensions-and-measurements/](http://www.bartneck.de/2019/04/21/lego-brick-dimensions-and-measurements/)
3. [https://snakeandboris.blogspot.com/2016/06/a-short-history-of-lego-brick-1949_6.html](https://snakeandboris.blogspot.com/2016/06/a-short-history-of-lego-brick-1949_6.html)
4. [https://brickarchitect.com/most-common-lego-parts/](https://brickarchitect.com/most-common-lego-parts/)
5. [https://www.instructables.com/How-to-Make-a-Lego-Ball/](https://www.instructables.com/How-to-Make-a-Lego-Ball/)
6. [https://rebrickable.com/sets/918-1/space-transport/?inventory=1#parts](https://rebrickable.com/sets/918-1/space-transport/?inventory=1#parts)
7. [https://rebrickable.com/parts/](https://rebrickable.com/parts/)
8. [https://www.thebrickman.com/736-2/](https://www.thebrickman.com/736-2/)

Thanks.

Post your makes!

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Changelog:

20250221: updated most of the 1x bricks due to a mistake on the first of the pins