Increasing number of Boolean fails

I have been using Rhino since version 3.0. I do some complex things and regularly build sections from extruded mesh outlines, using them to cut from solid forms. Over the past few months I have been getting more and more fails when doing boolean operations. I’m not doing anything different so i wondered has there been a change to the way the booleans are done, or a difference in the tolerances used for intersecting surfaces?
I have managed to get many of them to join by turning them into mesh objects and then doing a boolean on them, but this has the disadvantage of creating facets on curved surfaces which spoils the rendering.
I have a good example but Im not sure how to load it here so others can try …
[running V5 SR5 on W7Pro 32 quad core]

These are the two shapes im trying to difference - they dont seem complex at all!!

Just looking at your image, I’d say the near-concurrence of what looks like a faceted extrusion (the “U”) and the smoothly curved base part is part of the problem. Run Intersect on the two parts and examine the result.

There’s no reason why the “U” needs to have facets like that is there? I would remake that part starting from line and arcs and re-extrude.


Yep. I would also run ShowEdges, SelBadObjects on the “U”.

If this apparent change clearly occurred after an update, maybe something IS different in Rhino.

But if it has been gradually changing within the same version, then it obviously must be due to some changes in your own expectations, style, or technique. Or maybe just a kind of cavalier sloppiness is sneaking in with your increased confidence and experience.