Holes and Gaps

To 3D print a model, the input file must be one continuous, solid object, usually in the STL file format. The printer must be able to clearly distinguish between the inside and outside of the object it is printing. There cannot be holes or gaps in the model, because the 3D printer will not be able to tell what is inside the object and what is outside. This applies quite literally to something like a house - the exterior of the building must be sealed. Window and door openings, wall/roof intersections, chimneys, and the bottom of buildings are a few common sources of holes and/or gaps in a model that cause problems when 3D printing. Always check these areas, and the rest of a model, before moving toward 3D printing a file.

There are tools that can help identify and close holes and gaps, like CADspan, but the majority of these areas should be found and closed within the original CAD model for best results. It is far easier to fix these problems in the 'native' CAD program than to repair a STL file with holes in it. Even if resurfacing with a program like CADspan or Magics, results will be much better if the "input" model is completely closed.