I am trying to make a mold of the human airway. To do so I need to subtract the airway components from a block, then 3D print the mold. It appears that all components are hollow, is there a way to fill them in?


1 Answer 1


If i understand you, you have the airways components as one object and a cube that you placed around it.

If so, then i would believe all you need to do is the following:

  1. Select the airway components and go in edit mode
  2. Press A to select all elements
  3. Press Alt+N and select "Flip" to flip the normals. (the outsides become the insides and vice versa)
  4. Now go back in object mode and select the cube/block and the airways components
  5. Press Ctrl+J and you will have an object that considers the empty area the inside of the airways components as outside while the area between the outside of the cube/block and the airways components are considered inside and will be filled.
  6. There might be small parts that you will have to adjust, depending on where and how many outlets/openings you need for the airways components. That part should be easy to deal with if you loop cut or inset faces to generate enough vertices to connect the airways components outlets to the outside of the cube. Using "X-Ray" Alt+Z it should look something like this "very" simplified version.
    enter image description here
  7. To finish it, make sure to check the "Face Orientation" once more.
    enter image description here
  8. The outside of the cube/block should be blue and the connections from outside to the hollow airways components needs to be blue inside of their hollow parts, while if you go through the cube/block with the camera, it should show all red as you would move through the area considered inside the object where the 3D software (slicer) would give you the options to fill.
    enter image description here

It's important to make sure that no surface has red and blue colored faces on the same side! But the "Solid" check of the "3D-Print Toolbox" add-on will test for that.

Happy Blending.

  • $\begingroup$ Thanks a lot, that really helped! $\endgroup$
    – Tom Reina
    Mar 19, 2020 at 18:22
  • $\begingroup$ Happy to help, please consider to accept the answer if it solved your question. $\endgroup$
    – Xylvier
    Mar 19, 2020 at 18:33

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