Boolean Union Fail


I can’t figure out why the clear cover pieces won’t join in file case2 I was able to get it to work in case 1. I went back changed the radius of the rail I extruded along, that is the only difference. Any ideascase1.3dm (571.9 KB) ?

case2.3dm (571.9 KB) Continuing the discussion from Union boolean failed:


Oops I think I attached the wrong case 2 file here is the correct onecase2.3dm (619.0 KB)

(Pascal Golay) #3

Hi Will- are you union-ing the green outer edge to the blue inner parts? If so that will not work- there are coincident faces between the two. The easy way out is ExtractSrf all the coincident faces, from all the inputs, that are between the parts and then simply Join. Does that Make sense? Coincident faces cab be handled if they are planes but not in the general case.



No I am trying to boolean union the blue pieces together. there is a blue extrusion and a blue piece made from a sweep one rail. I could get them to boolean union in the file case1, but not in case 2. The only difference as far as I intended is the radius of the rail on the sweep.

Oh and can you explain what a coincident face is?

(Pascal Golay) #5

Hi Will- same story with those parts- there are surfaces on both parts that are exactly coincident- the edgeg faces that divide one object from the other. ExtractSrf those, and then just use Join.



OK that worked. So I deleted the edges basically making these open polygons, then using joint hey became one piece. I would not have thought it would have worked that way I thought join was simply for curves, not open surfaces. Also I don’t understand why it seemed to work on the case 1 with a tighter radius, but not on the case 2.

To explain coincident surfaces, is it that they each have a surface basically trying to share the same space. Is that what it means?

(Pascal Golay) #7

Yes- Intersecting surfaces that are exactly the same, even over a part of them, is tricky if you are looking for a curve of intersection. It is handled in the special case of planes pretty well.



Hi there i am having a similar problem with my 3d model. I have extruded each layer of contours and have been using the boolean union tool to join each layer/contour to one another. this has worked fine for 10 of the layers however i keep getting an error message when trying to boolean 2 of the layers.
I am unsure of why this is happening, can someone please guide me.

Boolean union fail 3d model

Some of the info here might help you figure out where the problem is…