Mig Welding: Find out everything about the MIG welding process

Mig welding is a wire feed welding process where you use a mig welder.

This would have to be the most used welding process in the world today. Using a welding gun, a power source, shielding gas and a constant feed of welding wire it's fast, simple and easy to do. It is the most cost effective and efficient way to weld.  Here is how Wikipedia explains mig welding.

The diagram below shows how the Gas Metal Arc Welding (GMAW) process works.

The technical name for "MIG welding" is actually Gas Metal Arc Welding (GMAW). You need to use a welding gas to shield the welding puddle and arc. Depending on the type of gas you use, either carbon dioxide or argon, then it can also be called "MAG welding".

MIG Vs MAG welding

So what is the difference? MIG welding is abbreviated for the phrase Metal Inert Gas, and MAG is abbreviated as Metal Active Gas. Some shielding gases mainly carbon dioxide and oxygen will react with the welding arc and puddle and help make the weld. So these are called active gases. But gases like argon and helium do not have any effect on the actual welding arc and therefore that's why they are called inert gases.

It is much faster than TIG or Stick welding and it can be adapted to robots and used in high end production facilities where part after part is repetitively manufactured.

How to mig weld

Want to find out how to mig weld? Well follow this link and go to my page that shows you how to mig weld.

 

 

 

 

Mig welding wire

Here we look at mig welding wire. Find out the more technical parts to why some mig wires are better than others.

 

 

 

 

Mig welder

If you need to find out what a mig welder is, go to this page.

 

 

 

 

Mig welding gun

Here on this page I have some pictures and descriptions on some of the different models of mig guns that are around in the world today. Some of the most common being, Binzel, Bernard, Tweco, OTC and Fronius mig guns.

 

 

 

Mig welding aluminum

Here are some basic tips that you need to consider when you want to mig weld aluminium.

 

 

 

Gasless MIG welder

Never seen a gasless mig welder before? This page has videos and photos of me showing you what one of thes mig machines are. I go over all the basic parts and controls showing you what it's all about.

 

 

MIG welding push or pull

Not too sure if you should push or pull the mig gun when you are welding?

To describe mig welding in the shortest amount of words it would sound something like this:

 

Some of the reasons why MIG Welding is so popular today are:

1. Very easy to weld using a mig.

2. Faster and quicker process.

3. It's more economical.

4. Can be used with robots and automation.

5. Can use a shielding gas to give very smooth welding bead appearances.

6. A variety of metals can be joined.

This is also known technically as the gas metal arc welding process. This is because you can use what is called a shielding gas which will allow for far greater control of the spatter. There are quite a few different types of gases that can be used today.

The mig welding process is great because of the fact that it allows you to weld in all positions. This means you can weld overhead, vertical up, vertical down, and horizontal positions with the one machine. Not only that, but you don't have to stop all the time to change electrodes, which is what you would have to do if you were using a stick welder.

One of the biggest things going is that there is less spatter when you are using a mig welder instead of using an arc welding machine. This is especially true if you are using a solid mig welding wire or a gas assisted flux core wire (FCAW). If you use a gasless welding wire, which is commonly used for the home welder, the spatter is around about the same as that of manual metal arc welding if not a bit more.

The welding wire feed speed is adjustable by controls on the front of the machine and once it is set it will constantly hold that speed, giving you a reliable feeding wire and allow you to put down filler metal so much quicker than stick welding.

Because of the fast travel rates that are attainable with this welding process the heat affected zone (HAZ) will be much smaller. This can reduce the chances of stress fatigues and weld failures later on. This is simply because of the fact that there's less heat input and energy going into the same welded joint.

A wide variety of metals and steels can be welded using this type of machine. To give you an idea of what can be welded you can do mild steel, wear plate, high tensile steel, aluminium, stainless steel, and even a variety of exotic and specialized steels and metals.

Thick plate can be welded with ease, right down to very small thin sheet metal thicknesses such as what is used to make car bodies.

Depending on what position you're going to be welding in and depending on the thickness of the material, you can use one of three main processes. What I'm talking about here is the function, or what happens at different temperatures, wire feed speeds and heat settings.

Starting off on the lower end of the scale is the first mode you come across is what is called short circuit transfer followed by globular transfer and finally spray arc transfer mode.

These are the three main modes of mig welding all of which have different uses and applications. For the DIY welder at home you are only ever going to be using short circuit transfer mode as this is suited to small thicknesses such a sheet metal and very thin plate. Now you know the mig welding basics you might what to learn how to mig weld.

Gasless MIG Welding

Another way you can welding using a MIG machine is when you do gasless mig welding. To do this you still use the same welding machine but you run a different welding wire. The welding wire in this case will be what is called a self shielding gasless mig wire.

This type of wire is very handy for the DIY mig welder to use at home because you don't need to go out and rent or buy a bottle of welding gas. But it's not only just limited to home use, it really is used by professional full time boilermakers and fabricators for certain jobs. The specification of wire is E71T-GS which means that this wire is good for single pass welding applications.

For multiple pass welding there is another grade of gasless mig wire you can get which is marked as E71T-11. This will have a slightly different chemical makeup allowing it to be used for welding over the top of existing welds. The normal single pass wire, you can still do multi pass mig welds over it, but the strength is not what it should be because each pass is will sort of be getting diluted if there is not enough base metal for it to mix with. The multi pass wire will account for the fact that you are welding over itself and thus why it has a slightly differnt chemical composition.

MIG Welding Polarity

Depending on what mig welding wire you are using you may have to change the polarity over on your mig welding machine. For us welders, polarity simply means which way around do I hook up my earth cable and my welding gun.

In normal mild steel mig welding using a standard ER70S-6 mig wire or similar, the wire also called the electrode has to be positive. Which means that the earth cable must be negative.

For gasless mig welding though as mentioned above, you need to change the wires around. So this time it needs to be negative for the wire and positive for the ground clamp.

You can notice a slight difference between the two setups if you try them both on one particular wire. So a good tip if you are getting bad welds with and what you think might be excess spatter when running gasless wire is to double check the polarity. Also when you start welding at faster wire feeding speeds and higher voltages and amperages in the spray arc transfer region you may also notice some issues there regarding polarity.

 The picture here shows how a solid wire with gas is earth negative and a gasless wire with no gas uses a positive earth connection.

Wire feed issues

One of the biggest problems you can have with a mig welder, be it a small single phase machine you bought from the hardware store or even if it is a large three phase industrial MIG, is the wire feed ability.

It is *** absolutely critical *** that the wire feeds through the torch smoothly without jerking and carrying on. The welding arc needs to be stable and constant all of the time.

See, the welding wire stick out determines how much or how little welding voltage there is at the arc. If the wire starts to become jerky and feeds erratically the welding wire stick out changes. This change in stick out or 'arc voltage' will have a negative effect on the weld.

So what are some of the most common causes of welding wire feeding issues?

Mig liner

1.  From the problems that I have seen myself out in the field the number one cause of mig welding wire feed issues is a dirty liner.  This is especially true for the workshops that are out in the country in all the bulldust.  I have been into welding shops and shed that don't have sealed floors.  They are just hay sheds that have doors, and when all the wind picks up it blows dust everywhere. 

All that fine dust gets onto the feed rollers and then is squashed onto the mig wire and is dragged down the liner to eventually clog it up.  Not only is that dust an issue but so is the general workshop dust such as plasma cutters and grinding dust.  All that stuff gets into the liner one way of another.

Here is a picture of dust and crud that has built up onto the drive rolls of a machine.  And yes this user did complain of welding wire feed issues.

 This picture shows the main drive roll on a single roll compact WIA mig welder.

You can see the build up of what looks like grinding dust and metal filings on the left hand side where the wire goes into the liner guide tube.

The groove in the drive roll where the wire sits seems to be okay and clean, but the unused groove to the front is full of dirt.

Make sure when you flip it around that you always clean it out.

What else can you do to help prevent this type of dust build up on the drive rolls. Well you should where possible get the machine up off the ground. I have seen so many workshops where the wire feeder unit is lying on the ground. Go and build your self one of those overhead ganty arms so you can hang the feeder unit up off the ground.

Picture shows an OTC wire feeder unit hanging from an over head welding arm, gantry or jib.

If you don't have a mig welder wire feed unit and only have what's called a compact mig (feed rollers inside machine with power supply) make up a stand or buy a mig welding trolley for it.

Get the wire spool covered up. Some wire feeders you can get plastic covers that go over the wire spool. This helps to stop getting onto the wire all the time.

Keep the door to the mig welder and drive rolls shut. If you live in a dust windy place maybe you can add some weather strip seal around the door of the machine if there is none already. This is an easy job to do as it has glue on one side of the weather strip and you can easily press it on once you clean up the surface first.

Another issue that you need to keep an eye out for is how straight the mig welding gun cable is. Ideally in a "real world" it would be coming from the welder as straight as possible. But unfortunately we don't live in a real world and having the torch layed out straight all the time is not possible.

Any unnecessary kinks, bends and twists in the gun cable need to be sorted out too. This all adds to the internal friction on the mig welding wire which makes it much harder to feed the wire through.

Also in the above photo the wire feed unit is hanging in a way that the mig gun is coming out from the fitting pointing straight down. This is a very good setup. I have seen places where the feeder units have been hanging horizontal and the gun cable has to droop down. When it droops down it make a sharp right angle bend towards the ground. And this gives you an area of increase area of friction on the wire as soon as it leaves the drive rolls. That is even before it gets twisted up and looped on the ground. Result, yes the person using this other welding machine was having wire feeding issues too.

Employee's are also lazy and don't give a toss about the equipment, I mean let's be honest. I had one guy drive over a brand new mig gun only a week or so old with a forklift (fork truck). Yes it's hard to get the workers on the floor to look after welding equipment, but it's stuff like this that costs you money and time. Yep they had wire feed issues after that one, and welding gas delivery issues too, ha ha.

So a lot of these issues all come down to common sense. Keep the unit clean, get it off the ground if you can and look after the gear.

Earth connection

2. Now another area to look at regarding the wire not feeding properly is the earth connection. You are dealing with an electrical circuit here fella's. You need a positive and a negative to make the "electrical loop" so you can weld. If the ground clamp is corroded or busted you may have wire feed issues.

Always clamp to clean metal

Imagine if it was not 100% clean, or you clamped it to some rusty steel or the steel had paint on it.

If it is a bad connection for whatever reason the welding arc will become erratic. Sort of like a light that flickers all the time. If it is doing this imagine what the tip of the welding wire is doing.

Instead of having the wire sit say 15mm from the weld puddle all the time, it might be getting closer then back up, then back down etc.

 If the ground clamp is loose, this could very well happen. You might feel the gun cable shudder and jerk about if you hold you hand around it when you are welding.

Again the incorrect and erratic arc will cause more welding spatter. It could very well actually hit the welding puddle as it can't burn up properly, and then your welds will really be bad.

Check for loose nuts, bolts, and corroded contacts

This welding ground clamp is brand new and on a machine. The copper ribbon cable has not even been bolted on properly from the factory.

Give them a quick check over for badly corroded contacts. If they are bad, clean them with a file or a sanding disc, flap disc or grinding disc untill they are shiny again.

Make sure the nuts and bolts are tight.

Clean Material

Another similar thing to having a bad earth connection is working on dirty metal.

If the metal you want to weld over has lots of rust, paint or grease and oil over it you will also have bad feeding wire.

This again is because the mig welding arc will not be able to burn through the paint and rubbish smoothly and evenly. This will cause the wire to start feeding like it is shuddering all the time.

 A little bit of surface rust may be okay but don't go welding stuff like this unless you clean it up first.

Also heavy coatings of galvanising are impossible to weld through. You have to grind it down to shiny metal.

The thin coatings on box tube is okay as this stuff burns off easily. Heavy coated stuff like the overhead rails in meatworks need to be grinded really well before you can weld them.

Dirty power

Another area to look into if you have a mig welder that seems to be having welding and wire feed issues that you may not have thought of to check, is the power coming into the welder.  I once came across a machine that was having funny welding wire feeding issues.  What we did to try and find the problem was replace the old mig gun with a brand new one.  We check to see if the feed rolls were not worn and that they were using the right sized wire for the drive rolls.  The new torch did make it a little bit better but it still did not fix the problem.

It was only a few months later when the machine was moved to a new workshop that the problem went away.  It turns out that the power that was coming in off the main road to the factory was not very “clean”.  Since going across town to a new shed with a new power line coming in the problem went away. 

So I guess this is not a really common issue, but it is worth noting in the back of your head.  Obviously not everyone can move their workshop across town.

Mig Wire

Here is an interesting topic about wire feeding issues on a mig welder regarding the type and brands of mig welding wire being used.

Okay, from the top you have soft wires and hard wires.  The soft wires are wires like aluminium, gasless, flux cored and metal cored.  Solid wires such as stainless steel and mild steel are much easier to feed through a MIG gun.

If you are using a soft wire you will need to use different feed rollers, either U grooved rollers or knurled rollers. 

Photo show what a knurled feed roller looks like.

This is so that you can get the maximum amount of traction on the wire.  If you use the standard feed rollers that have V groove, you will tend to over tighten the roller assembly.  This will mean you end up squashing the wire as well. 

Another tip for the softer aluminium wires is to get your mig gun shortened.  So if the gun is say 3 meters long, shorten it to 2 meters. Use a plastic or Teflon liner and an oversized contact tip, or a tip that is designed for welding aluminium.

You can also use a push pull gun on aluminium or a spool gun.

Now apart from the physical setup of the machine, regarding using the right tips, liners and drive rolls etc.  If you have the correct running gear the next step to look at is the quality of the welding wire itself.  I will tell you now that not all mig welding wires are the same, even if they have the same ER70S-6 code.  This is just what it has to meet, so the wire can vary slightly form brand to brand.

What about the wire diameter?  If it is inconsistent you will have troubles too.

Another point I want to make is the softness of wires even when comparing solid mig wires with each other.  You can pick up a roll of one brand of wire and compare it to another brand and one wire will be softer than the other.  Yep. It’s true.

Now a harder wire will punch through and push through any dirt in a liner easier than a softer mig wire of the same grade.The benefit of having a softer wire, and some manufacturers go to great lengths to make the wire soft, is that there is less wear and tear on welding consumables.A softer wire is less abrasive than a hard wire.The major benefit with softer wires is on robotic welding applications where machines run flat out all day and night.It's in those situations where a quality mig welding wire is critical. You can find out more about mig wire here.