Why does Boolean Union not work?

Hi, this object is not only one solid, there are many in these different colours you can see. I cant figure out why boolean union doesnt work or is there another way to do them together in only one solid body?!
Thankful for any help :slight_smile:

Did you tried to avoid booleans and exploding it in surfaces trim them with TRIM?

i tried, but now it is an open polysurface.

How is it open? Missing suface? Naked edges? Join needs to be used?

Boolean operations generally do not work properly with surfaces, particularly curved surfaces, which appear to be coincident.