Understanding units setup for STL I don't understand the unit setup. I need to print the model but its just still incorrect in dimensions.
I have set up length to millimeters unit scale 1.
Exported STL file in meshmixer shows that cube that has 100mm in blender is 0.1mm, how does that work?
Also, blender does not scale the model when changing the measurements.
e.g. A model that has 10cm when I change to millimeters it just show that it has 100mm. Do I have to manualy rescale?
Can someone enlighten me to how to set scale, units and grid size to actually work in the units and export in them as I want?
The STL format does not support units. It just records arbitrary X,Y,Z coordinates of the vertices for each face.  Blender cannot know the units you intend.

blender scenes have their own co-ordinate system.  Unit system and Unit Scale just offer consistent display of properties through the user interface.  The objects themselves remain unchanged, because equally these do not have real dimensions either, much like the STL file they just have an arbitrary X,Y,Z.

To fix the problem with your STL you must enable the Scene Unit checkbox in the STL exporter options as shown.  It is also worth using the Selection Only to avoid exporting unwanted geometry.

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Please note that the STL importer also has similar settings.