Update 2022-11-29
I've added a mirrored version, as the original version doesn't actually match up with the bracket unless its mirrored along the Y-axis.
Thanks CW-TTS!
I also added the step file as well (as the F3D file may not be useful for all). Note it will be in the wrong orientation when exporting to STL / 3MF and will need to be mirrored along the Y-axis!
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So, the APX-320 unit comes with a metal bracket that can be used - somewhat - for affixing to a wall, and maybe the joint between foam ceiling panels if they are used.
To affix the unit to a ceiling, or properly to a wall, requires the purchase of an additional mounting accessory.
So, this is designed to avoid having to do that. If the bracket is similar on the other APX models (120/530/740) then this will work for those as well.
It's a tight fit, and while it looks like it could be attached either way it needs to be in line with the UP arrow as indicated on the metal bracket.
The screw holes are big enough to use butterfly clamp screws for plasterboard.
Finally, I've uploaded the F360 file as well, so if you need to make some adjustments feel free to download and adjust away.
Print with supports everywhere, or if you like to be fancy, use prusaslicer to just print supports on the overhangs.
The author marked this model as their own original creation.