Concentric Rings Fidget (with or without center dome or keychain loop)

I have printed successfully with a standard 0.4mm nozzle at 0.12 layer height, no support, and 100% infill successfully without needing any post processing off the bedplate but your printer calibration may vary.  I was also able to print this successfully at 85% uniformly scaled down with no post processing as well.  Both scales just worked off the bedplate.  I recommend printing at 100% scale as I think it is more fun to fidget with. 

The 100% scale print takes about 2 hours for me at 80mm/s print speed.  I designed the model to compensate for any elephant's foot first layer squish to avoid fusing the first layer.

I settled on generating these stls with a 0.45mm tolerance between rings so that the rings spin loosely and freely.  I made it loose enough that I think most printers should be successful when printed with a fine layer height (0.12mm).  At 85% scale, the tolerance shrinks to 0.36mm.

If enough people like this design, I'll finish up my fully customizable source code and post that as well.

For reference, my kid prefers the fidget version without the keychain loop and without the raised center dome and printed at 100% scale.

Enjoy!