Modular Toy Robot Arm

Excellent design; it prints very well on my Prusa i3 MK3, which is not the most precise printer. Well, as mentioned in the description, you obviously need to snap it slowly with a knife blade, and I found a flat-head screwdriver very handy for prying the gears loose so they could turn. Then you just need to add a little lubricant and everything starts moving as intended. It works really well.
I took the liberty of reusing part of it to create the awards for our international scientific conference on high-throughput catalyst design, HTCD2026. A big thank you to the author @tmackay for this work. Your name will, of course, be credited at the awards ceremony.

I used a few parts to hold my ESP32 Cam in various positions to be able to watch the print via OctoPi.
I sat for a while overthinking and poring over others' makes to figure out what parts I needed to print. Here's an explanation of what I used as a jump off point for others.

I had to use an hobby knife in the seams of the round parts of the elbow. Do a few slices, try to pivot the elbow and listen for a "crack" sound as the author said, repeat.

Tip: If your joiner(s) fit too loose, melt a small dimple in them with a soldering iron to add friction to the fit. (edited)

PLA Nebula
layer 0.2
nozzle 0.4

Came out pretty well, I printed the base in Bambu Lab green PLA an and the rest in Sun black PLA. The gears in the base seem pretty loose, while the gears in the arms are pretty tight which is probably a good thing. Not sure if the slop in the gears in the base is intentional by design or because I printed it in a different PLA. Overall it came out nicely! Definitely took some patience and prying with an Xacto knife to get the joints loose but with how small the gear sets are I'm still impressed it works at all. Nice work!

What is the purpose of the modular joiner parts?

Can be made to print in ABS. Can be made to function through patience and caution. Gear lash is such that the knob has more than two turns(!) of play before the grip will crack loose; I didn't need any other joints so I didn't try. Your mileage may vary.

Very fun little model. Works great as a picture holder on a desk

Really great design! i printed it at 2x and use it as my robot assistant. Thanks!

Printed with supports around the turning knob first: mistake! 2nd print works just fine. The base is a bit wobbly.

Brilliant idea. My 2 year old son loves this.

Overall a challenge to print, but much easier when scaled 150% to toddler toy size.

Some honest feedback: One piece that I was not able to print without fusing was the wrist piece (even at 150%). I may remix and increase the layer gap between the pieces on this one and try again.

Still 5/5. (edited)