Inkjet printers for wire marking are not the same as the typical
desktop inkjet printer. They use a solvent-based ink that dries
essentially instantly. The printhead fires a continuous stream of ink
drops which are deflected by electrically charged plates, with the
unused ink drops being caught by a vacuum system and reused. The
machines are complicated and need a good deal of maintenance.
Consumables such as ink, make-up liquid to replace evaporated solvent
from the ink, cleaning solvent, filters, etc. are expensive. I don't
think this is a practical do-it-yourself project, and the commercial
equipment only makes sense if you're running a high-volume operation.
I think your best bet is to find a wire processing or harness-building
company that has not been driven out of business by imports from the
Far East and have them mark spools of wire for you. Try looking
through the membership list of the Wiring Harness Manufacturers'
Association to see if there's a company near you that can do the job.
http://www.whma.org/Membership/RegularMembershipRoster.aspx