I have a Taig DSLS3000 CNC machine, I am looking to use it to machine very fine details into a master for casting silicone rubber. For example, using a 60-degree V-cutter, I want to cut a V-groove with the sharpest possible detail (limited by the cutter, not the material). I would like to keep most defects under ten microns (~0.4 thou), or even one if possible. I realize the precision of the mill is lower than that but smoothness is more important than exact location here.
Since I'm casting silicone from it, any swarf or flakes etc left in the bottom of the groove will mess up the pour and / or tear up the rubber when I pull it out. Polyurethane leaves little slivers sticking out of the bottom, same with brass, the best I've found so far is epoxy but a) I have to clean it up by hand with a syringe needle afterwards to scrape out the compacted powder and b) it's epoxy and I'd prefer not to have that dust floating around, even though I have dust collection.
What is the best material for milling sharp features with minimal / no touch-up required afterwards? Or are there other approaches I should try (a grinding bit in glass or something)? Since it's for casting I don't really care about the other material properties unless it's toxic, too fragile to handle, or likely to catch fire in the mill or something.