So I'm pretty new to the whole 3D printing thing, and I was just wondering if only the faces will print when I use Blender to print a 3D model.

For example, if I take a basic cube from the template and print it, would a hollow cube be printed or a "solid" cube.

  • $\begingroup$ I'd say this belongs to 3dprinting.stackexchange.com as this is a general question about 3d printing .Partially related - 3dprinting.stackexchange.com/questions/953/…. $\endgroup$ – Mr Zak Jul 14 '16 at 12:25
  • $\begingroup$ Just as a quick addition, 3D printing only prints closed coherent manifold shapes, and unless the software used for printing provides any automatic shelling facilities it should print as a solid filled out object by default. If you need to add thickness to it I suggest manually modeling the inner shell yourself. The Solidify modifier may be a good starting point for simpler shapes and uniform thickness. For more complex stuff and internal support structures I'm afraid only manual modeling will do. $\endgroup$ – Duarte Farrajota Ramos Jul 14 '16 at 13:01

Mr. Zak is right that you'll get better answers on the 3dPrinting.SE, but the answer is that it will print a solid cube. Printing starts at one face, and continues until it finds another face (sort of). So if you only have one face, it knows where the material starts, but it doesn't know where the material stops. If you wanted a hollow cube, you'd have to specify a width for those walls by creating an inner cube with normals pointing toward the center of the object. The printer can't (won't) assume how thick a zero-thickness polygon should be.

It's useful to remember that all 3D polygons only have 1 face. This can be confusing, because there's nothing in the real world that works this way. That's why a single face is considered "non-manifold."

Duarte's answer includes the same information, but the terminology might not be familiar to you. A closed, coherent, manifold shape is one that is:

  • closed: all edges of all faces are shared by 1 and only 1 other face, like the default cube.
  • coherent: (essentially) it that has dimensions that can exist in the real world. Intersecting geometry, or geometry that has zero width is not coherent.
  • manifold: (basically) geometry that has one distinct "inside" and one distinct "outside." More specifically, all the normals are pointing the same direction. With the default cube, you have normals on the outside, and they are all pointing outside.

If you were to do this:

Non-manifold cube

You would have an interior face, with a normal that is neither pointing inside... nor pointing outside. Thus, this is non-manifold geometry.

For a more thorough a technical discussion of non-manifold geometry, see the answer to this question.

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