Here is my situation:
I place a cube of 20mm and then a cylinder of 2mm diameter and 22mm length through the center of the cube, extending 1mm from either side.
Using the cube as the "master" and doing a boolean difference with the cylinder works fine. The shaded model correctly shows the cylindrical hole through the cube.
I apply all transforms then do an STL export to view in either MS 3D Viewer app or CURA. Both apps show the cylinder ends protruding beyond the cube faces on opposing sides, no hole, just the cube face.
I also tried snapping the cylinder ends to the opposing cube faces in edit mode, then boolean difference in object mode. Blender displays it correctly as in the above procedure. Export STL and view in CURA et al, same result. No hole through the cube, in this case just 6 empty cube faces.
This is a simple example of the problems I'm having with a more complex model. Blender shows all the boolean differences correctly (3D Tools has no complaints) but the holes in cube faces and vacancies that should occur in the volume of the cube do not (render?) correctly in Cura or MS 3D Viewer.
I'm stumped! Is there a way around this situation?Cura render of first procedure
Thanks for your help! Dave