Can't connect 2 polysurfaces with boolean union. Help!

I have two polysurfaces, which I am trying to join via a boolean union.

Right now, the two polysurfaces are not overlapping so my understanding is that a boolean union isn’t possible. As proof of this, when I nudge the inside polysurfaces a few mm over, a boolean union is possible.

However, when I do a scale2D of the inside polysurface (so that it overlaps with the outer polysurface), the boolean union fails. That makes no sense to me, because it almost certainly is overlapping at that point.

Can anyone help explain what I’m doing wrong here?

booleanunion.3dm (357.5 KB)

not really sure what the problem is but i think, for this model, you’d be better off with an approach more like this:

…draw the pipes then using an arc, ExtrudeCrv through the pipe… then BooleanSplit the pipe with the curved surface… (delete the unwanted parts)… similar with the inner ring.
they union ok when doing it like this.

Hi Jeff:

Thanks for your help.

I’m a bit unclear what you did here. Specifically, I’m not clear how you created the inner ring and managed to get it 1mm tall (or whatever it is).

If you could please clarify a bit more, it would be appreciated.

does this help?

Yes, that’s super helpful. Thanks very much. (As a newbie, it’s crazy impressive to see how fast you put that together).

If I may just ask one more question, why do you use Boolean splits rather than using the trim/split command?

when the extrudeCrv was being used on both circles at once, the Solid option was on in the command… so, it was making solid pipes.

if you trim, the resulting halves won’t have a surface at the trim point and will no longer be solid… BooleanSplit will leave the intersecting surface in tact and joined to both halves of the object… both will still be solid.

WireCut is another option, it will do the closing and “solidifying” without having to use Extrude Curve and Boolean split. The downside is that it can only use one (joined) curve and one polysurface at the time.


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