MIG Welding Machine

Operating on a similar principle to other arc welders, such at TIG welding machines, the MIG welding machine offers considerably easier use – it can be learned quickly, unlike highly skilled TIG welding, and is straightforward enough so that it can be used in completely automatic welding processes rather than as a manual welding technique. The familiar images of robotic welders assembling cars in Japanese factories show MIG welding machines in action. Although it is simple and cheap, MIG welding does have a downside, however – the joins are not as strong as TIG welds, and they tend to be far messier, with large amounts of slag left near the weld site. This hard residue will destroy electronics if it becomes fouled in the wiring, so MIG welds cannot be used in electronics welding as TIG welds can, or in any small application where a clean weld is essential.

MIG welding machines are arc welders that use a powerful electric current to generate heat at the welding point – heat sufficient to melt whatever metal is being used for the project. The electrode that provides the heat is, at the same time, the filler metal that melts and bonds the two parts being joined. The electrode is therefore consumed while welding is going on, and in place of a permanent electrode, MIG welding machines are fitted out with a long wire that feeds continuously from a large spool inside the welding machine’s body, constantly melting its own tip into the weld while being replenished from the spool. An inert gas known as a shielding gas surrounds the welding point – this leads to the welding process’ name, since MIG stands for Metal Inert Gas.

Uses and limitations of MIG welding machines

A MIG welding machine is good for several different applications, and in all cases it is preferred over the higher-quality welds of the TIG welding machine wherever speed, low cost, and ease of use trump a very strong weld. Car factories are frequent users of MIG welding machines because a car chassis is not subjected to extremely strong forces, so it does not need exceptional welds, because the car body material is very thin, and because the MIG welding process is simple enough so that it can be carried out by robots.

MIG welding is close to a point-and-click style of welding and can be learned within a matter of days rather than through months of training and practice. The electric arc heats the tip of the wire until it is molten and runs onto the joint that is being welded, while rollers in the welding machine move more wire forward from the onboard spool. The melted electrode forms the welding pool that creates the weld, and the coating on the wire forms into a small cloud of gas around the welding point, ensuring that oxygen does not reach the molten metal. Argon is the usual “shielding gas,” since it will not burn or explode in the electric arc of the welder. It is dangerous if inhaled, however, since it can kill the brain by displacing all oxygen from it, or kill the lungs outright. Because of the need for shielding gas, MIG welding usually cannot be employed outdoors without building a special structure around the welding site to exclude wind.

Although MIG welding machines are quick and easy to use, they do have limitations thanks to their heavy deposition of slag on the surface of the object near the weld (which must then be scraped off, if possible), and because they have low weld penetration. MIG welding is best on thin metals, such as stainless steel, steel, and aluminum. Thicker metals and welds that need to be exceptionally robust – such as those that will be subjected to a lot of atmospheric or water pressure, as in the case of an aircraft or boiler – need the greater penetration and stronger welds of other welding techniques. However, it is excellent for many applications where an average-strength weld is sufficient, and small, portable models are ideal for the casual home welder.