I tried to model something like a cog. I created one tenth of the cog, mirror modified on 2 axes and added a circular array modifier to get the final result, using the merge option.
When I import the final model in Substance Painter, it looks as if the normals were off on the big flat surface. At least that's how I interpret it:
Any ideas what could be wrong here?
I checked, and all of the selected vertices below are on the exact same Z. Not their median, but the individual values.
If I simply create a circle mesh and fill it, I get a perfectly flat mirror surface:
Shading entirely smooth or flat doesn't seem to influence this issue: