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Here's a relatively simple model that I want to print (for bathtub drain). It is made by only creating cylinders and cubes and applying Array and Boolean modifiers.

the model

When I import it as .stl and load it to Slic3r (for correct result, scaling by 100000% should be used since .stl doesn't contain the scale), it shows this in 3D:

Slic3r 3D

which is ok, but there's warning which sais "Auto-repaired (18 errors)" and tooltip sais that "5 degenerate facets, 5 facets removed, 4 facets added, 4 facets reversed" and Preview shows this:

Slic3r Preview

and Layers shows this for the first layer:

Slic3r Layers

I wonder what I'm doing wrong and how to fix this. I haven't tried to print this yet, but the preview suggests that it will be no good. Here's the .blender file: .

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    $\begingroup$ This is likely due to non-manifold geometry. See also shapeways.com/tutorials/fixing-non-manifold-models $\endgroup$ – gandalf3 Apr 16 '16 at 20:38
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    $\begingroup$ You seem to have three different blender object pieces. Visually overlapping but not connected by vertices. Is that your intention? Is that acceptable to your 3D printer? $\endgroup$ – atomicbezierslinger Apr 16 '16 at 20:49
  • $\begingroup$ @atomicbezierslinger well my idea was to add the rim around the grid, but may be I should use the inner diameter for the grid, not outer; as for the central cylinder, it shoudn't be overlapping as I've substracted it from the "grid" part first and then "added" it and the hole inside it. I'm not sure about what's acceptable to the printer as I don't quite understand how the mesh and facets are converted to the "solid" detail.. $\endgroup$ – YakovL Apr 16 '16 at 20:58
  • $\begingroup$ Consider what I have submitted as beginning to your solution. Others can step in and help who have this expertise. At the moment my time here has expired. Can your printer understand n-gons or only triangles and rectangular faces? Keep practicing and testing your improvements. Keep searching here at BSE and youtube 3d printing with some of the new ideas from BSE. Consider seeing multiple video tutorials. $\endgroup$ – atomicbezierslinger Apr 16 '16 at 21:23
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enter image description here

Perhaps Multiple Problems. Edit Mode. Select Non-Manifold identifies some problems. See Arrow in image above. Add faces to holes you see.

enter image description here

Strange face. Edit Mode Face Selection. See arrow. Remove doubles can correct partially. Image above.

Look for more problems. This does not strive to be a tutorial.

Consider using Blender Mesh [Join]. Inspect each time with the menu choices of the first image.

Consider converting all n-gons to quadrangles or triangles. Quads and Tris.

Consider the Remesh Modifier. There is an Apply button.

Consider duplicating the mesh and making corrections to improve to the point when your 3D printer software has zero warnings. I do not have your 3D printing software.

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  • $\begingroup$ Wow. I've got the idea of how to find these, but didn't get how to fix these and why they appeared (like I said, I only created a cube and several cylinders and applied Array and Boolean modifiers). $\endgroup$ – YakovL Apr 16 '16 at 20:53
  • $\begingroup$ Thanks, I'll try this stuff, too (I have the bad version of the model saved) but you suggestion in the comments got me a much more straightforward solution (see the answer). $\endgroup$ – YakovL Apr 16 '16 at 21:36
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Boolean won't work with that amount of Ngons, doubles, intersections etc. See question with similar situation. It seemes it's a lot esier to recreate the mesh than trying to repair original one.

  1. Start with a plane and subdivide it so each subdivided cell is roughly the same size as cell of your original mesh.
    subdivided plane image

  2. Delete faces only (X > Only Faces). Add Skin modifier. Set Mean Radius for both axes as desired (0.05 used in this case). Set Branch SMoothing to something so there's no smoothing between shapes (0.66 used).
    skin modifier on subdivided plane

  3. After applying modifier you have clean topology which can be used by Boolean in particular. Place other meshes appropriately, add modifier and cut out what's needed (or not needed).
    boolean modifiers on subdivided and skinned plane

    Two Boolean modifiers were added at the same time; cylinder in the middle was hidden.

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Ok, thanks everybody for trying to clarify the misterious behaviour of Blender, but the solution was found using atomicbezierslinger's hint: just avoiding overlapping (man, I have no idea how this can be connected with those missing facets!).

My model (more precisely, the part I'd like to print) consists of 3 parts: the high hollow cylinder (C), the disk with holes (B) and the rim (A). In my first attempt, I've made the diameter of the disk with holes the same as the outer diameter of the rim. Second time, I've made it equal to the inner diameter of the rim. May be I've also changed the order of applying the modifiers, but second time it was: subtract the disk B (will be the grid) from the disk A (which becomes the rim), subtract the array of cubes from disk B (which becomes the grid), subtract cylinder C from the former disk B and hence this part is also read, add a cylinder smaller then C and subtract it to make C hollow. This way, A, B and C don't overlap and Slic3r shows a perfect result, too.

new Slic3r preview

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