Why does BooleanUnion fail given a closed extrusion and a closed solid polysurface?

I’m trying to BooleanUnion these two objects:


The cube is a closed extrusion and the other thing is a closed solid polysurface.

Here’s the file.

BooleanUnion Fail.3dm (81.4 KB)


I believe it fails because your cylinder and box are tangent.


If you move/scale slightly the cylinder the booleanunion succeeds:

It might as well be a tolerance/precision issue.

In this case and if you can’t move one of the objects as @ivelin.peychev says, you can use _Split first, then extratct the surfaces you don’t need:

and then use _BooleanUnion:

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I went with split first, then union.

Thanks for the advice, I’m back on track now.

It also works with file tolerance at 0.01