My results from using Michael's MakeRing script. http://moi3d.com/forum/index.php?webtag=MOI&msg=8370.1

I made 5 rings sizers on a Robo R1+ 3D printer to send to a customer to try on before making their real ring in titanium.

I modified the script to make 5 rings in 1/2 size increments. I also modified the shrinkage factor code to allow separate values for X & Z, as I found the PLA plastic shrink rate is not uniform in both axis.

After sanding the plastic sizers, I measured the inside diameter with digital calipers and all were within +/- 0.004".

Ed Ferguson