What is a Mig Welder and How Does it Work?

A MIG welder uses electricity to melt a welding wire that is used to connect pieces of metal together.

Though many continue to use the term MIG(Metal Inert Gas) when referring to this welding type, the proper acronym for the welding process is GMAW or Gas Metal Arc Welding.

The welder is a small, compact machine that easily plugs into a standard 120-volts standard electrical socket and with a 240-volt socket if the unit is designed to operate in both power inputs.

It feeds a wire electrode through an electrically charged contact tip into a Mig gun, which effectively transfers the welding current to the wire.

The wire is melted by heat produced by a short circuit in the electrical arc, and the welding bead is applied to the base metal being worked on.

Dramatic blue-lit MIG welding close

The weld is protected by a stream of inert gas to prevent contamination from the atmosphere.

Because of the need to shield the weld from the atmosphere, Mig welders are usually used in shops or enclosed welding areas.

The primary purpose of the shielding gas is to prevent atmospheric nitrogen and oxygen from getting in contact with the molten weld beads. These gases can cause a variety of problems like excessive spatter and porosity of holes within the bead.

The most common shielding gases are argon, carbon dioxide, oxygen, and helium.

Each of these shielding gases provides unique benefits and drawbacks in the process, so you have to choose the correct one for your welding application.

What is the Process for MIG Welding?

The Mig welding process is accomplished when the solid steel wire from a spool passes out from the machine and through the contact tip in the Mig gun.

When you pull the gun trigger, the contact tip becomes electrically charged and melts the wire to produce the weld puddle.

The puddle or weld bead cools when the heat is removed and then solidifies to fuse the metals.

Mig welding is a useful skill to learn because it can be used to weld many types of metals such as:

  • aluminum
  • stainless steel
  • copper
  • mild steel
  • bronze
  • other metal alloys

In comparison with popular welding types such as Stick welding, there are advantages, but disadvantages as well.

Mig welding advantages:

  • High productivity and efficiency from not having to change the welding rods
  • The ability to weld together a wide range of metal thicknesses
  • Mig welding is easy to learn and the welder is easy to operate
  • Capability to weld in all positions
  • Process creates minimal weld spatter
  • Minimal cleanup required after a welding project

Mig is an efficient and productive way of welding, but there are disadvantages to the process that you have to consider when you are planning to buy a machine.


  • Mig welder requires the use of an inert gas for shielding, which makes it less portable compared to arc welding that does not require shielding gas.
  • Mig welding applications are limited to thin to medium thickness metals. It is not appropriate for thick metal sheets because penetration is limited.
  • Less controlled process when compared to Tig (Tungsten Inert Gas) welding.
  • Uses costly consumables such as tips and nozzles, an inert gas for shielding.
  • Requires clean metal surfaces for welding.

What is a MIG Gun?

A Mig gun is usually included when you purchase a new welder.What is a Mig Welder

Some Mig guns may look like acetylene torches, while others are shaped like pistols.

Cooling is done by air or water, but for home welding projects,  the air-cooled gun is more appropriate.

You will need a comfortable Mig gun that fits well into your hands if you plan to take up welding seriously.

Read this review of best MIG welders available.

Mig welding is sometimes referred to as the “hot glue gun” in welding because it is quite easy to learn and master.

Once you have learned how to use a Mig welder, you can easily apply your skills in making simple repairs around the home.

After a while, you can start fabricating small, simple items such as brackets, stools, and small metal tables.

Here are some project ideas for beginners.

As your skills improve, you can move on to bigger and more ambitious projects and can even earn some money from selling some of the welded items that you produce.

Make sure you assemble and set the MIG welder correctly

Assemble the Mig gun prior to welding by sliding the contact tip over the bare wire, and then screw it into the correct tightness.

Put on the gas cup and screw it in front of the gun. Make sure that the contact tip is recessed down into the gas cup.

After you properly set the gun, you can turn on the inert gas supply and the welding machine. Choose the appropriate settings for the material and wire thickness for your project.

Prepare the spool by tightening the tension so that wire unravels smoothly. This ensures smooth and even wire feed.

Keep the wires as straight as possible to avoid tangles that can damage the line feeder. If necessary, cut and trim the wire with a wire cutter.

The wire must be properly aligned to ensure a smooth and consistent feed rate

Make sure that the wire you are using is free from grease and rust that will cause bad welds. To keep welding wires clean, remove the spool from the welder after completing a job and store it in a suitable storage container.

Wires left in the welder when not in use will become rusty and unsuitable for use.

Remember to keep the tension of the wire at the minimum amount that will allow the line to feed through. Too much wire tension can cause mountings to bend, which will damage the welder.

Your safety is important

One important point to consider before you start welding is the availability of a full set of safety gear for your protection.Set color icons of personal protective equipment

You need gloves, a welding mask, and protective clothing to prevent harm caused by arc flash and metal spatters when you use a MIG welder.

To prevent overexposure from UV rays generated by the welding process, make sure that your skin is fully covered.

Choose a welding mask with a minimum #10 shade or darker to protect the eyes from arc flash.

Include a vapor mask among the safety gear to minimize inhalation of toxic vapors during the welding process, if the welding site is poorly ventilated

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