Have you let Nikon know about your problem/issue?

chlamchowder wrote:

Yes, anything is possible, but I regard the possibility of plastic particles coming off as particularly unlikely.

Firstly, there have been many DSLRs with more plastic components than the D600. The D100/70/80/90, along with the entry level D50/60/3000/3100/3200/5000/5100 all share almost completely plastic bodies. We don't see complaints of outrageous dust problems from any of those bodies. What we do see are users of those cameras picking up the D600 as an upgrade, probably using it in the same way as the old completely plastic cam, and then seeing that the D600 suffers from far more dust than the old camera ever did. The fact that the dust problem is only shared between two cameras with plastic front plates, and no other camera with a plastic front plate, already makes the plastic particle theory extremely unlikely.

Secondly, with both plastic and metal, I can imagine shavings coming off if the surface is exposed to friction (grinding). That isn't what happens behind a plastic front plate (nothing to rub against the back side of it. Front side...maybe if the camera is really badly handled, but any particles would stay outside the camera along with the rest of environmental dust). I guess you can get fragments to come off a piece of plastic if you snap it, but that's not what happened. Softer plastic can absorb impact damage without denting or cracking like brittle metal. If anything, the metal bodied cameras would be more vulnerable (because of metal fragments from impact damage).