Hoe would you join these?

They won’t Boolean Union. The trimmed pipe was created by Boolean Difference between the pipes. They were copies an therefore identical. Short pipe is listed as “open polysurface”. Looks closed, and I don’t know where it is open, or how to close it. I’ve tried exploding a trimming etc. Anyway, the goal is to get them welded.

join.3dm (164.4 KB)

Hello - I’d go back to surfaces here - there is not a clean enough intersection and there are coincident surfaces right at the join. ExtractSrf then UntrimBorder and Intersect to get a new curve of intersection. Use that to trim both bits and then retrim the ends.

join_pg.3dm (122.7 KB)


I echo what Pascal has said. Alternatively, you can go to the top view, draw a straight line parallel to the the shape of the intersection, offset the curve, and trim away a bit from both pipes. Then, use _blendsrf with both edges set to “position” and join them up. But I’d go with Pascal’s method as the pipes need some cleanup and might create more problems in the rest of your project.

Use _showedges (select naked edges) and click on zoom to see where the open spots are.

join.3dm (184.6 KB)

Thank Pascal, but I don’t understand this. I’ve been trying solve it for over 90 minutes now. Though I’d like to understand your process, I had to move on and just started the part fresh. Frustrating, because I built the new one the same way I did the old and had no problems.

Hello - basically, if Boolean operations fail - (they are better all the time but for various reasons, they can fail - in this case the coincident surface is a problem) you can generally go back to the surface level and intersect/split/trim/delete/join as needed to get the result. That is what I did here - I untrimmed and then reintersected the pipes to get the red curve, trimmed both pieces with that and then joined and cleaned up.