set the undercut to Fine - NOT hd. It hardly make Any diffrence in the outcome, but no more broken burrs! Try it and you will see.
I have to admit that the ti base slots and crowns interiors as well are way to tight in pmma on m2 , but since it is a temporary restorations and it is v easy to adjust, I can live with that. But WHY is that
because as a rule milling undercut "automatically" in the majority of simplified CAM for dental, is basically useless. full of retract statements, very long toolpaths, lead-in statements that improperly account for machine capability to engage material at speed...
basically because they werent as fleshed out as they should have been.
i have the same problem with imes, dentmill, easyshape, and most of the other cam calculator software out there. until we got a proper version of worknc for which we paid dearly, i was unable to modify most of the strategies for milling. but now i can, and to be quite honest while the process has been difficult and tricky, i've been able to fix most of the tooling breakages i've had by not letting the system run strategies that came from the people who wrote the software.
i've also now identified a handful of proper actual factual bugs in the software that were new.
the point i am making is that you would do well to spend the money on the "full" license of whatever software you run on your machine, for the best opportunity to correct these silly things. initially it will be scary to open and play, but with enough time (i have now had full license for 10 months) you'll be amazed at the superior results you can acheive.
for example, by adding a 5mm tool to my titanium milling, i was able to clear out more of the area in a faster manner, and reduce my time spent roughing and finishing by a factor of 2.
also example: by increasing my cutter velocity in the roughing stage i was able to remove material from all my plastics and enable a nicer reach for my smaller tools, to access undercuts easier and with greater accuracy.
i wouldn't say these are necessarily things that took time and effort to do, although the titanium thing was rather touch-and-go. but i wouldn't say these were things that any person was unable to do either. i'm not special here. i just pushed buttons until i understood what did what, and how to undo that. that only took time to sit down and do some math and fiddle with the software. its like playing a game, it takes time to learn how to play right, and what the rules are. eventually you get pretty good.