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A Brief Introduction to MIG Welding

MIG welding

When you think of welding, MIG welding is probably what comes to mind.  MIG stands for metal inert gas.  It’s also referred to GMAW or gas metal arc welding.  It consists of a spool of wire that is fed, along with an inert gas, through a nozzle to the weld area.  With a mere squeeze of a trigger, an inert gas flow is started along with electric current and wire feed.  An arc forms between the wire and the base material; the wire melts but is continuously fed through the nozzle adding to the base material, while the inert gas protects the molten puddle from atmospheric impurities.  MIG welding can also be used without the shielding gas if you have a flux-cored wire; flux in the wire burns as the weld progresses, creating a gas shield around the molten weld puddle.

The ease of MIG welding allows for quicker and longer welds.  The only thing that really limits how long a weld can be is the duty cycle of the machine and the endurance of the welder, be it human or robot.

Because of its simplicity MIG welding is used in almost every industry.  Almost anything you can think of from cars and trucks, to farm equipment and pipelines, uses MIG welding.  It’s also incredibly easy to automate, making it perfect for repetitive, assembly line jobs.

The MIG welding machine is a relatively simple one, requiring a power supply, either gas cylinder or flux cored wire, spool of filler wire, and welding gun connected by various tubes and hoses.  The gun consists of a trigger to start everything, a gas diffuser that helps direct the gas to the weld area, a contact tip that the wire and electric current run through, all surrounded by a copper nozzle that protects everything.

The complicated sounding welding gun is supplied by the welding machine by a bundle of three things: a hose for the gas, a cable for the power, and a hose that the wire is fed through.  It’s important to keep the supply lines as straight as possible because the wire can get stuck in the feeder tube.

Unlike TIG, MIG welding uses a constant voltage power supply.  This means that the current can vary with the arc length.  The shorter the arc, the hotter it is, which melts the wire faster but since the feed is constant it forces the arc to lengthen.  This is true for the opposite as well, longer arcs will eventually shorten.  The whole point is to keep the arc at a very specific length so that the weld is more uniform.  Constant current power supplies can be used but they’re usually coupled with a device that regulates the speed of the wire feed to control the arc length.  Other various machines exist that allow for greater control when welding more difficult projects.

Once again Miller has a great series of machines for general MIG welding called Millermatic.  In particular the Millermatic 211 is a popular one for around the shop welding.  It has the capacity to plug into either 115, or 220V, which is great for portability.  The specs reveal that it can weld material from 0.8mm to 3/4 inch, or 9.5mm.  It works with solid steel wires from .023 – .035 in, stainless steel in the same size, and flux cored wire from .030 -.045 inches.  Another cool feature is called “Tip Saver”, which shuts down the output if the tip is shorted to the work.  This saves destruction of both tip, and delicate internal components.

Have fun with your welding projects and always remember to be safe.  Happy welding.

Written by Dustin Saunders

Ed

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