The Ring-A-Thing is a modular ring-building kit that will allow you to press-fit a small cube magnet into the base and glue a washer to the bottom of each design you make, allowing you to switch out designs on your printed ring.

It's parametric to finger diameter in mm, but I haven't yet figured out how to keep the diameter of the inset on the top of the ring stable for all ring sizes, so that you don't have to scale your designs.

I'm also going to see if I can come up with a better way of attaching the designs than the 3mm magnets, which won't fit inside smaller ring sizes.

Once those two issues are figured out, this project will be a go!

1: Open up OpenSCAD file. It's parametric. Measure the diameter of your intended finger in mm, add a mm for clearance, and type it in. F6 render, export new STL. Print.
2: Press-fit 3mm magnet into hole in ring.
3: Print design disc(s).
4: Glue design disc to washer.
5: Place disc into ring, where it will click into place.
6: To change designs, get a small screwdriver and pry up one side of disc until it comes loose. Place new design into ring.
7: Enjoy.