Very strange boolean fail

Rhino
1

Hello everybody,

I have a strange boolean fail here: I want to split a simple tube with a simple cuboid, but boolean difference fails, as well as boolean union. Both polysurfaces have no open or manifold edges and check finds them valid. If I run intersect I get the proper two circular curves.

What could this be? I enclose pics and the file.

Thanks in advance vor any advice - Jan
Boolean Fail.3dm (2.6 MB)

boolean fail
boolean fail624×560 113 KB

intersect

2

Huh…there’s something wonky about that cylinder, that isn’t being identified as ‘bad’ by SelBadObjects. If I Extract and Untrim the cylinder, it works. If I extract it and DON’T untrim the cylinder, the booleans “work” but give a bad result.

3

Did you notice that the untrimmed cylinder has sloping ends? @janneuffer: It would be helpful to know how it was made (i.e. has it been sheared, made from a mesh, shrunk to trim?)

4

Yeah…it functions fine as a surface alone, but the trim does something funny.

5

It was made from a simple cylinder, which was extruded twice with the gumball, then one of the caps was twisted by 30° in u, then by 30° in v and then extruded again. It is intended as a support for resin printing of an object which is also twisted twice by 30°. I found that if I trimmed off a part and then closed the opening, it worked again. But still a little surprising, that it is declared valid and doesn’t work … but I now found a fix.

Thanks anyway for you answers! Cheers Jan

6

Hi Jan,
The cylinder has edges with large tolerance.
Explode it and rebuild the edges, the boolean should work.

7

Hi Fabio,

thanks so much, I will try that!

Best regards - Jan