Boolean Union makes geometry smaller

Dear experts,

I am trying to union two meshes as one, however, after union nothing happened or one of them disappeared.

I really cannot understand what is happening.node.3dm (1.5 MB)

Wish you can help me.
Thanks and best regards!,

Attachment is my file.

On your model, I moved the parts together slightly and I got a union. You also need to check your face directions and ensure the arrows are pointing the same direction on each half or booleans do funny things.node-union.3dm (1.1 MB)

Hi Rob,

Thanks for your help.
It works.
Can you help me with this model?
When I use boolean ,one of them disappeared…disappear.3dm (2.3 MB)


Not so lucky with this one. I can’t get it to union properly. I’m not real strong on meshes, maybe someone here could give this one a go.


Well, running MeshIntersect gives you a clue. You get 43 intersections, including 5 open curves. The parts don’t “match” or overlap well. Unless the intersections can be resolved into a series of closed curves, any Boolean operation is likely to fail.