I brought some home-made magnetic spin toys to the Champlain Maker Faire last year, and they were a real hit with the kids. This was before I purchased my first 3D printer, so the only fabrication approach I could take was cutting disks out of plexiglass and super-gluing magnets to them.  Quite ugly.

This year, I wanted to use the 3D printer to create custom magnetic spin toys.  You can see all three generations in this picture:

Last year’s model is on the lower left.  My first attempt at a 3D printed version is on the lower right.  After I made it, I realized that it was much heavier than it needed to be.  The final version is shown in the back.

The three magnets press fit into the three arms.  Another circular magnet presses into the bottom.  Another magnet is on the base, oriented so that the red part floats on the repelling magnet field.  At the moment, I’m still using those base magnets to allow you to move the toys around on a metal plate, but I may create fixed toys with holes in wooden bases at fixed locations and distances.

Making 3D printed parts with precise internal diameters for the vertical shaft turned out to be impossible.  When I tried to drill out the shafts with PLA parts, they melted, so all of the parts must be made of ABS, with a higher melting temperature.

Aligning the shaft hole with the suspension magnet counter-bore also turned out to be too imprecise.  I ended up printing the shafts just undersized and drilling them out in two passes (so that the final pass took just a hair off).  I also eliminated the counter-bore for the suspension magnet and now glue that in place so that it is perfectly centered on the shaft.  The result are spin toys with absolutely no chatter or play, which spin for long periods of time.  Pretty close to perfection.

This video shows how they work: