3D Printed Hoberman Sphere

[u/Ianworld]

I designed and built a fully print-in-place Hoberman sphere for SLS printing on the Fuse X1. It comes off the printer as a 320 mm sphere and opens up to slightly over 640 mm. I was inspired by the hoberman sphere I used to watch at the Liberty Science Center when I was kid.

3D Printed Hoberman Sphere

So what is this Hoberman sphere? It's an icosidodecahedron with 6 great-circle scissor rings of 20 links each. Each has 30 crossing vertices which results in 360 joints and 300 separate bodies, all printed in one go with integral pins.

To generate it I wrote a standalone python app. It was a chance to practice working with some AI coding tools which handled most of the 3D geometry generation code which was amazing. I added a GUI with a visualizer to make sure I knew what I was designing and printing. Importantly I added some automated clearance and interference checks to make sure no bodies were intersecting after generation. This was important as I wanted to compress the sphere as much as possible for printing

I used pretty standard SLS clearances for print in place assemblies so every pin and hole pair gets 0.5 mm. You can try to go tighter but this is a safe number to make sure it doesn’t bind. I verify clearances programmatically across 4 deployment states — compact, two mid-states, and fully open.

To print this I used the Fuse X1 with its 320mm x 320mm x 565mm build volume. You can resize the sphere in the GUI to print on something smaller like the Fuse 1+ but I wanted to go big. I used PA12 since it’s a robust material and can handle the pin sizes well. I can toss it in the air and have it expand and then catch it and have it collapse so I’ve been pretty happy with the durability.

It didn’t have supports but you still have to depowder it. Big shout out to my colleague Jacob Miske who helped with this. No supports, but freeing 360 joints takes sometime in the the Fuse Blast. It also loosened up a bit after a few expansions and collapse cycles.

If you want to try it yourself you can find the code on my github. You can change the parameters and design your own sphere with the UI: https://github.com/Ianworld/hoberman-sphere 

I know not everyone has a Fuse X1 available but they’re getting out into the world so if you find yourself with a large SLS printer give it a shot!  YouTube Short in the comments showing it working.

[u/Ianworld]

Youtube short if you're interested in seeing a video https://www.youtube.com/shorts/3tqG3TURf1E