Why Wire Feeders?
Unless you buy an "all-in-one" Millermatic® welder, you'll need a Wire Feeder to complete your wire welding system.
In fact, good MIG or Flux Cored welding depends on smooth wire feeding performance and the weld procedure controls contained within the feeder.
If you're fighting problems related to erratic arcs, crater cracking or poor starts, a new wire feeder could be the solution.
And note that different wire feeders have been designed to meet a variety of needs: hard wire, aluminum wire, pulsing, portability, dual-wire and boom-mounting.
See also MIG and Multiprocess
No Need to Check this Bag at the Gate — New Suitcase Feeder Goes Everywhere...