Simple Fan Guard

Fan guards don't get much simpler (and less restrictive) than this design. It will keep things like fingers out of the fan, and sometimes that's enough. I added a built-in spacer to set the guard back from the fan. Sometimes the rotor sits above the level of the frame mounting holes.

The arcs are segmented rather than smooth, and it is thinner than the original, but other than that should do about the same job as the original. If you want it thicker, scale it in the Z direction.