Enclosure for Prusa i3 MK3 based on 30x30mm stock aluminum extrusions

I had thought about an enclosure for my MK3 for quite some time and when I started learning how to use FreeCAD this idea turned out to be a nice study object. As time went by the project was getting more and more detailed - and time consuming :-) ...
The design is done in FreeCAD version 0.17.13541, released on 2018-08-16 - and I am happily sharing the .FCStd source files so that other enthusiasts or FreeCAD trainees can have a detailed look without being limited to STEP-files.
The design appr