I have 2 objects. They have some edges and faces in common (but also some differences of course). I can merge these with ctrl+J. I can then do 'remove doubles' to remove the double vertices.

However, this way I end up with double faces and edges.

For example, I have a face of model A and an edge of model B. The edge of model B is in the same plane as the face of A and the edge of B also goes through the edges of the face of A.

I would like that the edge of B cuts the face of A and its edges, so that the edge of B becomes a part of the edges of the faces of A. That way I can do further editing on the model.

A 'manual' fix is possible but then I'll have to it over 150 times which is a bit much.

So, is there a simpler automated way to do this in Blender? I've searched a bit around but I don't even know how it's supposed to be named, so all tips are welcome.

The end result will be a 3D-printed lens adapter for a vintage lens so the accuracy of the model is rather important.

Thanks in advance!

Update: My goal is to merge the light and the dark blue parts.

The boolean operator seems to work fine with basic cubes, but it fails when using it with my more complex model. Depending on whether I set the normal of the dark blue ring on inside/outside it either doesn't work (throws error) or it gives a weird results with only around half of the faces shown. Looks a bit like This recent problem. I've applied scale and normals with ctrl+A and ctrl+N.

  • $\begingroup$ ok I just had a look at the blend file : is merging them manually acceptable for you (without loose the vertices positions) ? $\endgroup$
    – lemon
    Jun 25, 2016 at 6:28

3 Answers 3


As I cannot obtain any good result with the boolean (starting from Blue Fox's file), I propose this editing approach.

The steps below are in the layer #15 of the blend file :

enter image description here

  1. The objects are still separated. Open the faces to be merged.
  2. Relocate the upper mesh and merge the two
  3. Select the upper opposite edges and CtrlE and "bridge edge loops"
  4. The same for the lower opposite edges
  5. And the same for the last opened part, but without the extremities, because of the needed ngones at these extremities
  6. Make faces for the extremities (select manually the vertices and face F)
  7. Remove doubles

This is not a real answer of the question (more or less "how to make the boolean work"), but the job is done. No vertices were moved.

I have noticed these here :

  • Face centers with no face (maybe construction points ?), surrounded by O
  • A plane, is that printable (1) ?
  • And in (2), the inner faces overlap

enter image description here

  • $\begingroup$ This approach did the job! Thank you very, very much for your effort! It makes working with Blender a lot more doable for a beginner like me. Also thanks for the suggestions for 3D printing. $\endgroup$
    – Blue Fox
    Jun 25, 2016 at 7:55

You can try to union your meshes with the boolean modifier.

Here is the principle :

  • Select the big cube in the center
  • Add it a boolean modifier
  • Select another cube (this one shares a face with the previous one, but they are not merged for now) as the object in the modifier
  • Select the operation type : "union"
  • Click apply

enter image description here

Same thing for the shares edges :

enter image description here

Depending on the complexity of your models, this may work or not.

Note : the bad thing is boolean modifier does not keep quads. So for instance, if you want to do other operations after that (for instance Bevel, subsurf, ...) it will not work very well..

  • $\begingroup$ Thanks! This seems the way to go. I tried this with some simple cubes and it does what I want it to to. But I get some weird results with the boolean modifier and my (rather complex) model. It removes part of the model and in the terminal I get errors like 'groud 0xa86214c8 is unclassified!'. It also seems I'm not the only one with this problem, so I'm searching for a solution. I already tried scaling (and apply scale) 100 times but this didn't solve the issue. $\endgroup$
    – Blue Fox
    Jun 24, 2016 at 21:06
  • $\begingroup$ @BlueFox, eventually try to see if it is a normals problem (edit mode, select all, ctrl+N). But as I said in the answer "Depending on the complexity of your models, this may work or not." $\endgroup$
    – lemon
    Jun 25, 2016 at 6:20

To remove doubles:

  1. go to edit mode on youre mesh
  2. press space on youre keyboard
  3. type: remove doubles
  4. click on it
  5. you're done
  • $\begingroup$ Thank you for your comment but sadly this doesn't fix the issue. I expected this to work and tried this a few times but it didn't, as was written in my original post. $\endgroup$
    – Blue Fox
    Jun 24, 2016 at 21:31

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