[BurrMan]

I tried the merge you suggested, and just looking at the file you sent - I'm afraid I don't see what the difference is.

It bothers me that, even with the 0.0001 tolerance that you mentioned, when I post the toolpath I get three G3 moves (X,Y,I, and J) at every Z depth rather than one simple G3 circle (I and J) at each depth. Plus, if I pick just the upper two inside surfaces (the only part I'm really trying to mill) and a ball nose end mill, the toolpath stops with the ball tip at the bottom edge of the second surface, rather than extending below it as is required to mill the full surface (doesn't matter whether I use Tool Tip or Tool Center in the parameters). Guess I will try again on the BobCAD forum, as you suggested, and see if anybody else picks this up.

I just posted a quick video over there for them to see. It will also a better ploace to get the answers about the posted G3 and how those can be controlled or what not. I dont really know Gcode very well.

The video has a tidbit at the end to show you continuity in an exaggerated way.. You should probably just ignore that part of my response. It doesnt seem very relevant to what you need.

As far as the depth, yes, the toolpath wont go "Past" the selected surface geometry. The way i would handle that is to leave all 3 surfaces selected, then use the "Botton of Job" setting withing the feature to stop the toolpath where I want. So if you have a ball and wanted to stop the path at the top outer edge of the ball mill, you could calc that. I also suspect you will then see a difference when selecting "tool center" because the geometry selection allows the toolpath to goo "Past" that endpoint... If not, then that can be presented in the BobCad forum for a proper answer,,,

https://youtu.be/2x6rDxOnod4