One of the advantages to MIG welding with a wirefeed welding machine is that the filler metal spools continuously off a supply in the main body of the device, and is carried forward to melt in the welding arc by an arrangement of rollers and other fittings designed to keep the wire passing smoothly from the drum to the welding pool.
This means that, within the limitations of the duty cycle (the length of time the welding machine can keep running before it needs to shut down in order to cool itself off), you can weld continuously without needing to stop and reload another stick or pick up a fresh rod if you are feeding the filler metal into the pool manually.
The wire extending from the end of the welding gun needs to be kept at around half an inch long at all times. If it becomes longer, you need to snip it shorter with pair of side-cutting pliers. Keep a pair of these pliers conveniently to hand at all times when carrying out MIG welding. Remember, however, that you cannot stick the pliers into an active arc without risking electrocution.
Failing to keep the wire trimmed back properly can lead to a contaminated, weakened weld that will not last as long as a properly applied bead should.
MIG welding gun handling techniques
The proper grip for using a MIG welding gun is to hold it with both hands. One hand should hold the gun directly and be used for fine control, while the other hand should hold the main hand in some way in order to keep it steady and stable. This will also increase your comfort and lessen your arm fatigue during lengthy welds, or brief welds at awkward angles.
To use your welding gun properly, you need to have a good view of the weld and in particular the welding pool at all times. A small welding pool is a sign that your arc is too weak and that you need to increase the power. A large, very liquid welding pool means that you need to dial back the heat quickly before you blast a hole clean through your workpiece a hole that cannot be repaired with MIG techniques but needs a TIG repair to handle it properly.
Managing the welding pool
To get a clear view of the welding pool, you need to look past your gun, not directly at the back of it, and look slantwise at the pool so that gases don’t obscure it from your view. This is especially important if you are using flux cored wire, which will produce intense clouds of smoke at the weld site which could hide important information from you.
The start, or root, of the welded joint is always a problem with MIG welding because of the cold start and lack of a welding pool. Dial up the heat intensely at the start of the weld, then, when the metal becomes molten, shut off the arc and let the pool cool off for around 2 seconds. Then, resume welding at normal arc intensity, which should give you a good, hot welding pool without it being so hot that you blast a hole in the start of your weld.