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I'm trying to create a template for a rubber stamp mold as in the following figure enter image description here

The idea is then to import an SVG curve which will be given a Z-dimension, and placed inside the template as in this figure: enter image description here

Then, the SVG mesh will be subtracted from the template using a boolean modifier. However the difference modifier does not seem to work, giving the message "Cannot execute boolean operation". At first I thought this might be due to conflicting normals, but I have checked this. I have also made sure there a no non-manifold faces.

I decided to eliminate the solids in the object one by one, and I discovered that I could delete all of the letters except "INL" and it still wouldn't work. enter image description here

However, once any of the remaining letters are deleted, the difference modifier works as expected. Why does it not work on all the letters together?

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  • $\begingroup$ Have you tried remove doubles? $\endgroup$ – GiantCowFilms Dec 5 '14 at 1:44
  • $\begingroup$ And converting the curve to mesh (Alt+c) $\endgroup$ – Scalia Dec 5 '14 at 1:45
  • $\begingroup$ @GiantCowFilms Yes I have. At first it deleted way to many vertices because of the scale, but using the correct scale about 230 vertices were deleted with no noticeable loss of detail, but the problem persists. $\endgroup$ – pcurtis8 Dec 5 '14 at 1:47
  • $\begingroup$ @Vince I forgot to mention I had converted the curve to a mesh already for extrusion. $\endgroup$ – pcurtis8 Dec 5 '14 at 1:49
  • $\begingroup$ By the way, I'm also working on a pretty small scale (mm). I noticed that by scaling everything up I can get the difference to work on the 3 letters together. But no such luck with the original mesh. $\endgroup$ – pcurtis8 Dec 5 '14 at 1:54
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I solved my problem by simply subsurfing the cylinders I used to make the larger object.

Explanation:

In the original design, you can see that the circular faces are whole (not subdivided into quads or triangles). In search of another solution using the knife projection tool, I discovered that it does not work well on whole faces, and subdividing the face was the solution there. It then occurred to me that subdividing faces might help the boolean modifier approach. In fact it did work: the only other caveat was that the top surface of the cylinders aren't subdivided by the Subdivide command - you have to use the Subdivide Surface command first.

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    $\begingroup$ I believe that the reason the subsurf fixes the problem is because it creates quads, Booleans don't work nicely with n-gons. In my mind the best way to create quads in the circle would be to delete the n-gon circle and replace it using the grid fill tool. This will give you much cleaner topology than subsurf and won't quadruple the geometry. $\endgroup$ – PGmath Dec 6 '14 at 12:37

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