Step 2: How the Machine Works

A MIG welder has a couple of different parts. If you open one up you will be able to see something that looks like what is pictured below.

The Welder

Inside the welder you will find a spool of wire and a series of rollers that pushes the wire out to the welding gun. There isn't much going on inside this part of the welder, so it's worth it to take just a minute and familiarize yourself with the different parts. If the wire feed jams up for any reason (this does happen from time to time) you will want to check this part of the machine out.

The large spool of wire should be held on with a tension nut. The nut should be tight enough to keep the spool from unraveling, but not so tight that the rollers can't pull the wire from the spool.

If you follow the wire from the spool you can see that it goes into a set of rollers that pull the wire off of the big roll. This welder is set up to weld aluminum, so it has aluminum wire loaded into it. The MIG welding I am going to describe in this instructable is for steel which uses a copper colored wire.

The Gas Tank

Assuming you are using a shielding gas with your MIG welder there will be a tank of gas behind the MIG. The tank is either 100% Argon or a mixture of CO2 and Argon. This gas shields the weld as it forms. Without the gas your welds will look brown, splattered and just generally not very nice. Open the main valve of the tank and make sure that there is some gas in the tank. Your gauges should be reading between 0 and 2500 PSI in the tank and the regulator should be set between 15 and 25 PSI depending on how you like to set things up and the type of welding gun you are using.

**It's a good rule of thumb to open all valves to all gas tanks in a shop only a half turn or so. Opening the valve all the way doesn't improve your flow any more than just cracking the valve open since the tank is under so much pressure. The logic behind this is so that if someone needs to quickly shut off gas in an emergency they don't have to spend time cranking down a fully open valve. This might not seem like such a big deal with Argon or CO2, but when your working with flammable gases like oxygen or acetylene you can see why it might come in handy in the event of an emergency.**

Once the wire passes through the rollers it is sent down a set of hoses which lead to the welding gun. The hoses carry the charged electrode and the argon gas.

The Welding Gun

The welding gun is the business end of things. It's where most of your attention will be directed during the welding process. The gun consists of a trigger that controls the wire feed and the flow of electricity. The wire is guided by a replaceable copper tip that is made for each specific welder. Tips vary in size to fit whatever diameter wire you happen to be welding with. Most likely this part of the welder will already be set up for you. The outside of the tip of gun is covered by a ceramic or metal cup which protects the electrode and directs the flow of gas out the tip of the gun. You can see the small piece of wire sticking out of the tip of the welding gun in the pictures below.

The Ground Clamp

The ground clamp is the cathode (-) in the circuit and completes the circuit between the welder, the welding gun and the project. It should either be clipped directly to the piece of metal being welding or onto a metal welding table like the one pictured below (we have two welders hence two clamps, you only need one clamp from the welder attached to your piece to weld).

The clip must be making good contact with the piece being welded for it to work so be sure to grind off any rust or paint that may be preventing it from making a connection with your work.


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<p>Absolutely great instructable, especially for the beginner - thanks a lot! But I have possibly the most idiotic question of all that was not answered. I had a stick welding crash course some two years or so ago and they taught us to calculate the space between the electrode and the workpiece. It' such a f**k. Now, in MIG-Welding DOES THE WIRE TOUCH THE WORKPIECE or do you have to maintain a space just like in Stick welding? I know it's a stupid question... Thanks everybody in advance.</p>
<p>The wire touches the workpiece in MIG welding</p>
<p>&quot;A grinder and paint, makes me the welder i 'aint&quot;</p>
<p>love it!!!</p>
<p>Where can I find more info on flux-core mig welding?</p>
<p>Great tips in here!</p><p>though one incorrect tip is opening the valve halfway; you should open it <strong>all </strong>the way or you will lose shielding gas</p>
<p>Thanks! I used to weld for a Scene Shop that made stuff for cruise ships. Everything from stage trusses for lights to massive props (e.g. a &quot;rock&quot; that opened up to be a winged monster, whose mouth the dancers came out of!), to massive, curved stair cases, lit, with inch thick plexi treads....</p><p>I haven't welded in ages and seriously miss it. So, I was brushing up, in case they'll let me stop by and play with their equipment on a couple of projects I have. Either way, I appreciate the great info and it should help lots of people. Cheers.</p>
awesome information for beginners <br>
<p>Thank you for this! It's a great intro for me, a woman-of-a-certain age group wanting to take up welding! </p>
In regards to Gas Tank Regulator Valves, An oxygen setup should always be opened completely so as to seat the stem of the valve against the packing. Failure to seat the internal stem's packing will likely cause a leak-resulting in a potential large scale explosion. The potential of a leak is more common than one would think. Imagine your garden spigot that you water your pansies with. Open it all the way and it usually works fine. Turn it a just few times and, usually, it drips-not a big deal. It's just a little water right? Apply this situation to your stuffy garage. You are welding a few things and the phone rings. 30 minutes later, your garage is a blasting cap just waiting for ignition. You get back to your work, strike an arc, and all of a sudden, you see a white light and your late grandmother welcomes you &quot;Home&quot; into God's kingdom. Now, we all would like to see Grandma again but I'm sure she can wait a few more eternities before you show up. Now, I'm not saying all regulator setups will blow you into grandma's arms again, but the Oxy-Acetylene setups are potential fatalities- now you know.
i was reading the comments just to see if someone let them know that the value should be open all the way, can be very dangerous. the value works both way up and down
<p>Aside from Acetylene, which should only be turned 3/4-1-1/2 full turn, Most other tanks should be opened fully or they will leak. He also mentioned Oxygen as Flammable, which it isn't. It's an accelerant, which is different. Still not something you want around flames though, or grease/oil, because then it can become explosive.</p>
<p>Thanks for the tutorial ! </p>
<p>I am a bigginner welder and I am looking for welding helmet, come across <a href="http://weldinghelmethq.com/" rel="nofollow">here</a> and see some choices, please tell me which one is the best. Thank you !</p>
<p>this is one of the better &quot;how to welds&quot; ive seen on the internet. most are so full of errors and misconceptions or ignorance its crazy. good to see that you did your homework. and took the effort to make a good instructible. :)</p>
so much valuable info
<p>noahw did a fantastic job with this instructable. @psik - because you don't understand welding or the instructions in the article, doesn't make them wrong.</p><p>I will clarify some basic things for you though since you don't understand what the rest of us do.</p><p>1) The electric arc is caused by a short circuit. That's what electric welding is; a controlled short circuit.</p><p>2) CO2 is used a shielding gas, even with pure steel. Oxygen prevents a proper weld, so inert gas is used to push it away.</p><p>3) When he said to increase the pressure, it means increase the gas flow. Increasing the pressure of the gas is achieved by turning up the flow.</p><p>Do try in the future not to insult someone else's work simply because you misunderstand it.</p>
<p>Although it is very helpful, this Instructable has many erroneous information like:<br>- heat is generated by short circuit - not true, electric arc is a heat source in welding<br>- 100% Argon or a mixture of CO2 and Argon is used as a shielding gas - not true, for steel pure CO2 is mainly used to heat up the arc. It's also much cheaper than Argon<br>- you have to increase pressure when there is not enough shielding gas - not true, you have to increase gas flow instead</p>
<p>Nice write up!</p><p>Now for fun, here a video of how NOT to weld.</p><p>https://www.youtube.com/watch?feature=player_detailpage&amp;v=Us7VDZT-NcQ</p>
<p>HG, I hope you defied them at your high school and took welding anyway. Recently reading about women and painting in the early part of the 20th century when women were expected to do pastels and water color. Oil was deemed to difficult for women to undertake. </p>
<p>The 20 CFH you mention is a very good starting flow and the correct default setting for most mig welding. Depending on gas mixture, stickout and nozzle position relative to the tip you might go as high as 25 cfh, but any higher and you risk getting a venturi effect that sucks in room air and further decreases weld quality.</p>
<p>Interesting point. Thanks. </p><p>BTW I think that converts to just over 9 l/min for the rest of the world.</p>
<p>Great instructable, thanks for putting all this info together</p>
<p>Thankyou for sharing this info about welding! When I went to high school in British Columbia, Canada welding, carpentry and electricity plus drafting was offered in school. I had a space in my schedule that would accommodate these interesting &quot;crafts&quot;. However, I was mocked and jeered for putting my name on the list SINCE I WAS A GIRL. Hesketh, the principal of my Junior High School, laughed and mocked me in an all school assembly. I felt very ashamed that I had made the request. He singled me out for wanting to learn the basics of &quot;manly crafts&quot;. At the time, I was unaware that my Father's family had for generations in Canada and Eastern European been noted craftsmen in this field of interest. It was within me. Nevertheless, after that public humilation, 20 girls signed up for the same courses. Unfortunately, I was leaving the Junior High School and entering the Senior High School, where same stupid policy was in place. So, thankyou once again for sharing. Some of us, are just born with the natural yearning to learn these so called &quot;manly crafts&quot; as well as being an expert on vacuuming, washing the dishes, laundry and crafting a decorative 4-5 layer sponge cake. I can also plough a field and milk a cow. And, I have changed the oil in my car several times including changing the filters. Handigirl. </p>
<p>Handigirl, the way you were treated is nothing short of disgusting! Ones sex should not matter whatever the craft or skill. My god, where would we have been if not for all the wonderfully skilled women mechanics, welders, lathe operators and engineers during World War 2? I am a 52 yr old male who does not underestimate the power of any other man or woman. I can weld (gas, MMA and MiG) but I can also sew and love it. I also bake a very nice coffee cake :) These are all human skills not male or female skills.</p>
Handigirl, good for you! I would be proud of any of my daughter's to take on that task. Btw my Mom (Mum for our friends in Canada) was a welder during WWII along with many other women.
<p>I forgot to mention, TIG has (IMO) the steepest learning curve. While it can be just one hand for autogenous welds, it can involve up to both hands and a foot, so if you weren't a drum set player in another life, it might be a tough thing to get started with. Stick isnt bad once you learn to strike the arc, but IMO again, mig is by far the easiest to pick up for a beginner. Worth trying that in a class next time around.</p>
<p>Most courses require but do not provide PSE (Personal Safety Equipment). Which is honestly good for you, as the class would be much more expensive if they did. In my experience for a mig class, you'd be expected to show up with a pair of safety glasses, helmet, vice grips or pliers, mig pliers (AKA welpers) a steel brush, mig/stick gloves and a jacket or at least long sleeve shirt. Some also require or recommend a welders cap. For what its worth, starting with TIG IS probably the hard way, and both mig and smaw(stick) are though different from each other, easier to pick up than TIG.</p><p>Lastly, a word regarding cost. When you price out buying/renting a tank of gas, a professional level wirefeed unit, a high quality power source, a decent mig gun, the regulator/flowmeter, an endless supply of coupons(metal pieces to weld together for learning), the consumables such as tips, nozzles etc, the spool of (presumably) ES-70-6 or similiar for mild steel that you might use up or more often make welding classes a real bargain. And any PSE you buy you keep for after the class.</p>
<p>Almost all welding requires a proper welding helmet / goggles. Most guys buy their own but in any classroom they should be available along with proper FRC coveralls.</p><p>TIG needs a little more co-ordination than mig or stick but I would have stuck with it if I were you as once you master that the other forms of welding would have been much easier.</p>
Sorry but o2, oxy is not flammable but an oxidizer which helps things burn.
<p>Great 'ible' Thanks for taking the time.</p>
<p>Great intro.</p><p>Only exception I have is the all position comment. </p><p>Sure if you are not too bothered about integrity but for a fully qualified weld I would say no. I have some great pictures of overhead welds done with mig that look fine for profile etc. etc. done buy welders with years of experience, but all of which failed. v-up gives better pen. but v-down with mig is often just a cosmetic weld that can be useful as a cap for a v-up. </p><p>It sure is easy to learn though. Back in the 70s my instructor told me &quot;Ya can teach a monkey to mig weld&quot;</p><p>Its also great for large gap / bridge welds to lay down something to backfill where stick would not cut it or you don't have something to use as a filler bridge.</p>
<p>I think this article is really well done. You did a super job of it and this should bring people into MIG quickly, and easily. The only caution I would sound is that you made it sound SO easy people may not think that having an experienced welder around the first couple of times is needed. I do think it's needed. You can make a friend, get some tips &amp; tricks and keep it safe...all at the same time! Find your nearest Maker/Hacker Space, check it out and see if they've got this gear already for you try before you buy, with an experienced facilitator at your elbow. Once you've got your &quot;sea legs&quot; underneath you, the sky is the limit!</p>
<p>Having just read the instructions for MIG welding I have to say it is a load of rubbish. Why do people think they can weld when it is very clear they cannot. I speak as a teacher of fabrication and welding (15yrs) my first year students after correct instruction would lay a weld 100 times better than what has been shown here. You guys out there that want to weld correctly, take the time and do an evening course at your local college. </p>
Always clean your nozzle after every weld and when changing your tip. A clean nozzle prolongs the life of your tip and ensures a quality weld. A clogged nozzle also restricts your gas flow causing porosity.<br>
<p>I have written so many articles on welding procedures <br>but after reading this article felt like never knew anything about MIG welding. <br>Great job author.<br><br>www.red-d-arc.com</p>
<p>This has been so helpful to me. I'm a freshmen in high school and I take welding class, I have gotten past my other 1st year class mates and I moved onto mig welding and this has helped me greatly. </p>

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