Every desk fan has it. What's the purpose of the white cap attached to the front fan grille?
it just provides a center for the radial wires to meet up at. It could just as well be a ring of wire but this is more decorative. My silver fan has a slightly more complex one.
I think it's cosmetic, to cover the wire ends, and it's even carried over to moulded plastic covers. Some fans with expanded metal grills don't have it:
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