Normal Map Baking doesn't work at edges I tried a lot of stuff already but I can't seem to figure out how to bake a clean normal map.

As for testing purpose I used the starting cube ;-) beveled it for the high poly version.

I marked all seams, unwrapped the cube with some padding.
After that I baked the normal in Blender.

But as you can see it looks totally weird and doesn't give me any clean edge. I read and watched a lot of tutorials but with most of them, the baking "just works". Any idea what could go wrong here? 

As my testing environment is super simple already, I'm kind of lost on what to try...

Cheers Daniel
Baking the normal map with a cage seems to resolve most of the shading errors I got earlier.
To do this check the cage option in the render tab under baker und set the extrusion to some fitting value. 0.05 did the trick for me.

Still wondering why such a simple object creates such huge shading errors though (yeah I know 90° angles everywhere..but still)