I’ve never tried to make a tool path using Grasshopper before. Don’t like Anmeone though (component-to-component iterations quite slow) so I tried using the Slider animation instead, and expanding a horizontal Pipe along the curve (evaluating a new extended sub curve at each anim step), then split off upper part of the pipe, keeping only the lower half, then extruding the edges upwards, and Boolean Difference the full “tool path” at each step. Looks a bit smoother than “dip cutting” at each step, although I don’t know if this approach is useful for anything apart from the groove looking a bit smoother.
Inspiration taken from Josephs definition " ball bit 0.90_anemone_2020Aug31a.gh" which I modified (removed Anemone replacing it with a slider animation):
A step-wise prolonged Brep (half-pipe + extrusion) does the milling:
Milling With Ball Point.gh (21.1 KB)
// Rolf