How To Set Up a MIG Welder – A Technical Guide

Unless you weld for a living, it is often difficult to know if your MIG welder is set up for optimal performance. If you find yourself asking questions such as “am I using the proper voltage?” or “do I have too much or too little wire?” then this article is for you! We will touch on the basics of properly setting up your welder, and then look at what your weld bead is telling you.

How Will I Prepare the Joint?

Machine set-up only works right if you have a properly set-up joint. Ideally, you want all rust, paint, oils, dirt, and mill scale removed from the weld area. This is done for three reasons:

• The first is a clean joint produces a clean weld.
• The second is that the machine settings will vary between dirty joints and clean one.
• Finally, a dirty joint will spatter and spit increases the chances of you getting burns or starting a fire.

Do I Have the Right Gas and Electrode/Filler Wire?

A major part of setting up your machine is choosing the right gas and filler wire/electrode. This is an area that varies depending on all of the above factors and many more. The three most commonly used gas/ electrode variations or combinations are:

• Carbon Steel – ER70s Electrode with a C25 Gas (75% Argon and 25% Carbon Dioxide)
• Stainless Steel – ER308L with a C2 Gas (98% Argon and 2% Carbon Dioxide)
• Aluminum – ER4043 with 100% Argon gas

How to Set Up a MIG Welder?

There are three settings or controls that set the welder and those three are:

• Voltage
• Wire Feed Speed
• Gas Flow Rate/Gas Type or Mixture

These three settings are what control the heat of the weld and depending on what gasses are used the transfer type too. If you are not familiar with transfer types then please read up on MIG Welder Transfer Types because they have a big effect on your settings and how you will be welding.

Newer machines like the 211 below no longer need to control wire feed speed and voltage. You just turn the dial to the thickness you want to weld and tweak it from there. The machine does everything but regulates the gas flow.

Voltage Settings and Polarity Type

To start the voltage type used is almost always D/C electrode (+) positive. This means that the handle is the positive side of the circuit, or it may be said, the electricity flows from the metal into the welding handle. This setting almost never changes and if you do need to change it then you need to unbolt the internal leads and flop them.

The voltage is the main heat setting that gets changed depending on the joint, metal thickness, gas type, and position of the weld. It does most of the regulation and is most commonly used to change the welder’s settings.

The voltage setting varies depending on what size electrode is used, how thick the metal is, and what type of gas is used. Since MIG welders are CV or Constant Voltage power sources, the voltage does not fluctuate very much when welding.

Wire Feed Speed

The wire feed speed regulates how much or how fast the wire is feed into the weld joint. Wire feed speed is regulated in IPM or Inches Per Minute. The wire feed speed also serves another purpose for regulating the amperage.

When Stick or TIG welding, the main setting is amperage, but it is the voltage that fluctuates depending on the arc length. With MIG it is the voltage setting that stays the same but the amperage changes depending on the wire feed speed and electrode stick-out.

Since you don’t want to change the wire, select one for your most commonly used thicknesses.

30-130 amps: .023 inch
40-145 amps: .030 inch
50-180 amps: .035 inch
75-250 amps: .045 inch

Gas Flow Rate/Gas Type or Mixture

Finally, the gas type and gas flow rate help regulate the transfer type. A high percentage of Argon or Helium added to a mix creates a hotter arc. The main goal of the gas setting is to provide enough gas to shield the weld area from the air.

Gas flow rates are regulated in CFM or Cubic Feet Per Minute. This is an area that requires experimentation. In a shop setting a rate of 15 CFM may be enough, but a drafty area might require a rate of 50 CFM. Another thing to watch for is not to have the gas setting too high.

A flow rate that is too fast can cause turbulence and suck in air to contaminate the weld. Having the right gas flow rate is a trial-and-error process that is ultimately a search for a happy medium of all settings in the current welding conditions.

Putting the Voltage, Wire Feed Speed, and Gas Flow/Gas Type Together

Finally, once these settings are all put together it produces the transfer type we wanted and it has enough heat to properly penetrate the metal without burning a hole through the joint.

It is the result of trial and error that experimentation ultimately sets the machine just right to produce the weld we need, want, or hope to make.

That all sounds fine unless a welding engineer or procedure has done all of that work for you. If not, then it is time to look at the next section; MIG Welding Charts, Settings, and Guides.

MIG Welding Settings Chart

Finally, if you need some exact answers and guidance then you can read this! The manufacturers of most welding machines include either a MIG welding Settings chart inside of the machine or a guide to their machine settings.

I do want to mention that two identical welding machines that are made by the same company at the same time never run the same. These are only guidelines and do change from machine to machine! Each machine is calibrated differently and that all depends on its use and who has serviced it.

For wire size	Multiply by	Ex. using 1/8 inch (125 amps)
.023 inch	3.5 inches per amp	3.5 x 125 = 437.5 ipm
.030 inch	2 inches per amp	2 x 125 = 250 ipm
.035 inch	1.6 inches per amp	1.6 x 125 = 200 ipm
.045 inch	1 inch per amp	1 x 125 = 125 ipm

What Type of Metal Will I Be Welding?

The type of metal that will be welded has a big impact on the machine setting, electrodes, and gasses that will be used. Different metals have different melting temperatures and hold that heat differently.

When setting up your MIG welder you need to know exactly what type of metal you are going to weld. There is no single setting that works on every metal type. The three most commonly MIG welded metals are:

• Carbon Steel/Commonly Designated as A 36 Grade
• Stainless Steel/Nickel Based Alloys
• Aluminum/Non-Ferrous Metals

What is the Metal Thickness That I Will Be Welding?

The thickness of the metal has a major impact on the machine settings. When it comes to other processes like Stick or TIG welding you can use almost the same setting for a variety of metal thicknesses. For example, you can weld ¼ in a thick plate with the same setting used to weld a 1”-1-inch-thick plate, and so on.

Now MIG welding on the other hand does not work this way! The heat settings vary greatly depending on the metal thickness. The biggest danger from a weld quality standpoint comes from using too low of a heat setting.

For example; in the Nuclear Power Plant building industry, MIG welding is almost banned. This happened because in the past there were many welders who did not use enough heat and ended up welding joints that did not penetrate at all.

The weld looks fine but a few taps with a hammer and the joint falls apart. Even a proper spot weld would be a lot stronger! MIG welding too cold will put in the weld, but it is only lying on the surface of the joint. To cold of a weld is as useful as duct taping the joint.

Examining the beads

One way to check your parameters is by examining the weld bead. Its appearance indicates what needs to be adjusted.

• Good weld: Notice the good penetration into the base material, flat bead profile, appropriate bead width, and good tie-in at the toes of the weld (the edges where the weld metal meets the base metal).
• Voltage too high: Too much voltage is marked by poor arc control, inconsistent penetration and a turbulent weld pool that fails to consistently penetrate the base material.
• Voltage too low: Too little voltage results in poor arc starts, control and penetration. It also causes excessive spatter, a convex bead profile and poor tie-in at the toes of the weld.
• Travel speed too fast: A narrow, convex bead with inadequate tie-in at the toes of the weld, insufficient penetration and an inconsistent weld bead are caused by traveling too fast.
• Travel speed too slow: Traveling too slow introduces too much heat into the weld, resulting in an excessively wide weld bead and poor penetration. On thinner material it may also cause burn-through.
• Wire feed speed/amperage too high: Setting the wire feed speed or amperage too high (depending on what type of machine you’re using) can cause poor arc starts, and lead to an excessively wide weld bead, burn-through, excessive spatter and poor penetration.
• Wire feed speed/amperage too low: A narrow, oftentimes convex bead with poor tie-in at the toes of the weld marks insufficient amperage.
• No shielding gas: A lack of or inadequate shielding gas is easily identified by the porosity and pinholes in the face and interior of the weld.

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