Ok, this one was fun. It's big. Each of the small cubes is 100mm on each side, making the whole thing 200mm a side.

I made this while testing out tolerances on things and my tolerances here are a unnecessarily precise.

It is intended to be printed one piece at a time and assembled. It works great fully assembled.

Printing

There are 8 small cubes, 4 left and 4 right.

Supports will be required for the vertical cutout. I used snug supports, auto generate. I tried trees from the base, but they just didn't work as well.

They aren't necessary for the small holes on the vertical cutout, so check that they weren't generated – they shouldn't be.

The hinges. You need 8 hinges, so print 8 of the 39 or 40mm, not both. The 40mm fit exactly with zero play if everything goes perfectly. The 39mm fit easily. Both have the same gap between their holes, so there is no functional difference.

The hinges when I print them friction fit into place. It would probably work great to shrink their height by 0.5mm.

Assembly

Extra parts required here:

• 5mm x 25mm dowel pins – 2 per shaft per hinge, so 32 total
• 4.5mm x 18mm springs – 2 per hinge, for 16 total

The springs sound insanely specific, but I built this around the size used for ball point pens, because those can be had in bulk a lot cheaper than any other size.

Anyhow, put a sprint in the middle of one of the hinges. Put a dowel int the hinge on either side. Press them together until the dowels are flush with the edge of the hinge. Slide that into one of the cutouts until the dowels pop out into their sockets. At this point that hinge is never coming out again. Repeat for the other side of that hinge connecting to another cube. Repeat for all 8 cubes and now you have a megacube.

I suggest using another fidget cube as reference for the layout of the cubes. It is very much possible to connect them in a way where the cube won't work.

Print Profile

I printed it at 25% infill to make it heavy. This was overkill. While it does have a satisfying weight to it, it is too much and will smush fingers. Not dangerous, but certainly not comfortable.

My prototypes as I was figuring things out were at 5% infill. This actually works very nicely, but it's possibly to punch a hole in the cube if you so desire.

In hindsight I would go 10-15%.

Cubic infill, so it is equally strong in multiple directions as it has no constant orientation.