I am making a custom case for a Raspberry PI and PI camera for Octoprint. I have made the Pi case as a separate part, and the camera case as a separate part. I tried then to make an assembly of the two parts, and used constraints to glue them together in the appropriate manner. Then I exported an .stl file from this assembly so I could 3D print the new assembly. The stl file had all sorts of errors (triangles not manifold, overlaps, etc.). When I sliced the file and printed it, the print was a mess of goop. Both parts were fairly complex, which probably accounted for the issue, but there is definitely a problem in Alibre exporting an .stl file from an assembly.
I did not report this to Alibre because I dropped maintenance this year (due to financial considerations). Knowing I would receive no support, I decided to not spend the time to document this and package it up for Alibre support. The thought here was that even if they did fix it, I needed to get the part finished and would never get the fixed version of Alibre anyway.
I then tried to use boolean add to add the camera case to the PI case (inside the PI case part) and then export the .stl file of the new part. This gave me the same result as making an assembly and exporting the .stl file-an .stl file that contained so many errors that it was unusable.
Since I didn't want to fool around with this anymore, I then decided to open the PI case part, and manually add the features of the pi camera. I did that, exported the .stl file (the .stl file contained NO errors), and it printed correctly. Anyway, I got the part I needed, but it was a pain. Actually, a boolean is similar to an assembly.
There is clearly a problem in the way Alibre exports .stl files from booleans or assemblies. I have had some that have worked ok, but not this time. I don't know if this a general export problem, or just for .stl files.
Now I know that I need to create the entire part, not try to assemble part in order to get a good .stl file.
Steve