As a note of caution, if you are printing plastic parts on a filament
or stereo lithography printer, particularly if there are thin sections,
the part may leak.  Other than the surface layers, the layers in a
printed part are not solid.  The percent that is solid can be adjusted
when the build file is created.  Therefore, you should either program
the internal to be solid or seal the part before you use it.

Jack Breen