I've attached here (in the .zip file) a 3DM with that one more difficult cutting surface just moved up slightly so that it does not have any area where the knurl edges skim right along the surface, now it should trim without any extra messing around needed:



But depending on what you want to do with these pieces it seems like you may want to have a 2D cutting curve instead, the 3D cutting surface is banking around and adds a kind of extra angle to the cut up result, that may make it more difficult to get the results connected up to other pieces - a 2D cut will be more uniform and simple in its result.


You could get the one in your original position to work but it will probably involve a fair amount of clean up work, you'd need to generate the intersection curves and then go in and clean up the messy parts and then once you've got a good curve with no overlapping/backtracking type pieces in it use it as the cutting object.

- Michael