Why does boolean union keep failing?

Rhino Rhino for Windows
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1

rg6.3dm (17.8 MB)

image
image1920×1080 193 KB

I want to join this flowed solid, but it keeps failing!!!

2

Hello - if you intersect the two, you’ll see that the ends need to be cleaned up - leave the ends open, and make sure the ends meet up cleanly in the design.

rg6_PG.3dm (1022.0 KB)

-Pascal