I loved the idea of a 3D printed fidget infinity cube, but was sorely disappointed by the models available on Thingiverse. Some printed well enough to turn, but none had been optimized well for 3D printing. I set out to create my own version, with tolerances and hinges designed perfectly to turn right off your print bed.
Prints at 0.2 mm layer height and takes about 4.5 hours. Please let me know your results!
UPDATE 12/19/2017: Fixed a couple of internal walls that were causing issues with certain slicers. Thanks to @th_in_gs for the help!
UPDATE 3/31/2018: If you're using Cura, be sure to disable "Ignore Small Z Gaps" under your "Shell" settings! Thanks @runtimeterror for discovering this fix.
This thing is optimized for 0.2 mm layer height. Please try that first before any other resolutions. It's also optimized specifically for a 0.4 mm nozzle width, so no guarantees it will work well if you're using another size.
20% infill gives it a tiny bit of heft so it feels better to spin around, but you could probably go up or down from this number depending on your preferences.
Some other tips for best print results: use a skirt that's close to the model and goes up 5-10 layers, keep part cooling fan off for first layer then on for the rest, turn the model diagonally in your slicer so that X and Y axes move together for most of the moves, use 3-5 vertical shells/perimeters to avoid curling, and print at the coolest temperature you reasonably can for your material to avoid stringing or lamination where it's unwanted.
Break free and loosen it up
The cube's hinges should all turn freely straight off the print bed. However, you can get it a lot smoother by grabbing an individual pair of hinges and working them back and forth repeatedly to "wear" them in.
This model was designed 100% in Tinkercad. I used cubes of 3.2 mm radius along with a lot of cylinders for holes and pins, plus a lot of handwritten calculations to ensure even tolerances throughout the part. For example, the radius of each cube is equal to the outer radius of each pin, so that the corners do not interfere when rotating (as they did on many other models I tried printing).