I was pointed to this article.
I downloaded the files and thought this might be a challenge for AlibreCAM (VisualCAM). The perimeters and flat surfaces are pretty easy with a few different ways to skin the cat so to speak.
But how to do the splines. I find that selecting 3D machining and the inner and outer perimeter with a 30 degree tool creates open loops.
How does one go about setting up this kind of machining operation?
The file is too big to include so I've put it here: