Lumps on fan blades - benign o̶r̶ ̶m̶a̶l̶i̶g̶n̶a̶n̶t̶?̶

[bearer]

Noticed the new 3-wire 12v fan I ordered for my Hemera has these small blobs on the blades and I wonder if this is for balancing the rotor maybe, or just a manufacturing defect?

(edit: its a fan off digikey, not some random ebay/ali seller)

The other side of the blades are perfectly smooth.

[Kolbi]

Some fan blades have those to reduce turbulence, reducing noise. Hard to see the positions on the blades, but they might be that.

[arhi]

as kolbi said, those are "sound modifiers", manufacturers are trying different things from adding those blobs on the different position of the fins, to adding ridges on the fins, teeth on the fins...

[bearer]

Thanks for the input; sound or balancing was the first thoughts, but the dots are of varying size and locations, and only on 5 of 6 blades so I'm not sure anything made sense.

But I eventually stumbled onto

which seems to suggest someone just had a bad day at work while (over) balancing it and getting it right on the 5th try.

Oh well, specs say it moves the same air as the original, sounds about the same but has tachometer output so I can monitor it. Happy times ahead.