Very Basic Mig Question

I have been reading some of the posts in this welding section, and one thing has come up a few times that confuses me (doesn't take much). You guys talk about using so many "amps" and a certian "wire feed speed". Now I have an old sears AC buzz box, that I've been using for years for my own bubble gum welds, and my knowledge consists of this "thicker steel means more amps and bigger dia. stick electrodes. Burn through-- lower amps" My son has a little Lincoln 125 plus mig welder with argon/co2 bottle that he uses for thin steel, and the only controls on it are VOLTS and WIRE FEED. Where do the amps (heat) come in? And if I'm burning holes, what do I turn down, or, in the opposite situation, (not hot enough) what do I adjust? Thanks, JR49

I am an occasional welder, so I might not know what I'm talking about.
I've probably said amps when the dial indicates volts, JR. I was confused because my TIG welder says amps.

It doesn't really matter. It does, but not regarding how you adjust the machine. If your power knob says volts or just has a number, then that's the only control you have over the heat of the arc.

If welds aren't penetrating and piling up on top of the material, then turn up the heat some. If they are burning through, turn it down. It is usually a good idea to maintain about the same ratio of feed and volts that are shown on the chart that is probably on the inside of the spool cover door.

So, if it says 50 for volts and 7 for feed for one thickness material and it is burning through, go to the next lowest recommended setting (maybe 40-6) and change both. Only experience and experimentation can tell you how to make independent adjustments. The sound it makes when welding is a very good indicator. It should sound like steady bacon sizzling, sort of. An even crackle. If it is popping and making an unsteady sound, the wire feed is probably too slow. If you can feel the wire jabbing the weld, it is probably too fast.

Wire feed is measured in inches per minute, but the feed dials are just convenient numbers.

One very important thing I've discovered is to keep the hose to the gun as straight as you can. If it has a sharp bend, it can effect the steady feed of the wire. This is often indicated when part of the weld is going well, then all of a sudden, becomes lumpy and crappy.

There are lots of good uTube MIG welding videos out there. Watch some.

I am hoping that Chuck jumps in and enlightens us all.

As I understand it stick and TIG are constant current machines, you select the desired current and the machine attempts to keep the current roughly constant.
While MIG uses a constant voltage machine, it lets you select the voltage and the machine tries to keep the voltage roughly constant.
Of course with changing arc lengths it can be difficult to keep either truly constant.

The lower-end (home owner/hobby machines) do not allow you much control. The manufacturer figures it out and give a chart, you start with that and weld then tweak, then weld, etc.

The high-end professional machines let you control everything and add more advanced features like DC pulse (and even pulse-on-pulse!), pulse amplitude and frequency control, AC duty-cycle control (balance).

Chuck?

-brino

brino said:

Chuck?

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as the speed of the wire increases, the amperage increases. decreasing the wire speed decreases the amperage. WFS, wire feed speed, must be known in order to run at the correct amperage if your welder does not have an amp meter. Small changes in wfs can make large changes in amperage.

Miller has a welding calculator app for free that gives wfs for mig, and settings for tig and stick

Generally the faster the wire speed the more current that the MIG welder produces (up to a point), however having said that, it is also dependent on a few more factors, the voltage selected and also the wire thickness and also the wire stick out from the metal to be welded which will cause the arc length to change and also the resultant amperage.

So once you have a rough ball park figure of wire speed and voltage that you have set, do a small test bead. If the bead is too tall adding a few more volts will flatten and also widen the bead, also increasing the amps assuming that the travel speed is not changed. If you bring the torch closer to the work to shorten the arc length (up to a point) the amperage will also increase. Increasing the wire speed will also increase the amperage, and you may be able to travel faster without getting a taller bead.

So there are several ways to to achieve (more or less) the same result. Different wire sizes have a very rough ball park figure in which you can set the ratio of wire speed to voltage to weld properly, but they overlap and you can select or fine tune those setting to suit the job at hand. For example, you would not use the same settings for a spray transfer on a flat butt weld to do a vertical up hand weld or overhead weld. You would select a ratio which would give you a cooler short circuit weld transfer. So to sum it up very broadly, increasing the volts will increase the "heat", whilst increasing the wire speed will increase the "amps" but both of those are also related to each other, I hope that I have explained this properly and that this sort of makes sense, most MIG welders know what to do but it is a bit hard to explain. Just my 2 cents worth!

Cheers

Thanks to you all, for the great education, I put all your responses together and printed it. Can't wait to get to my son's place to "play" with his mig, and use all this info. I'm thinking a mig welder, slightly larger than his, might be in my future. Any suggestions for a beginner ? Happy Memorial weekend, JR49

Hi JR49,

JR49 said:

I'm thinking a mig welder, slightly larger than his, might be in my future. Any suggestions for a beginner ?

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I always try to avoid the red vs. blue debate. I believe it comes down more to the product you have used before, rather than one company being light-years ahead of the other. And also which one is readily available........here the "big box" warehouse stores sell the Lincoln and it regularly goes on "sale".

With that said, I have the Lincoln 180 MIG. It has been just right for me. I have done many spools of steel wire, some aluminum(with a spool-gun) and also some stainless. I mostly do solid-core, gas shielded simple because for small precise things it is SOOO clean, no smoke, no spatter, no chipping hammer! However for some things (like the trailer that was in my driveway last week) the flux-core made sense; cheaper with no shield gas, don't have to worry about the wind affecting the shield gas, and who cares about a little smoke and spatter....I'm outside and it's a trailer!

Mine is a fixed 240VAC input, which has been a little inconvenient on one occasion; remote welding and needed to build a large, long extension cord...but now I have it for next time.

About the only thing I would do different is to get the Lincoln "180C", instead of my "180T". The "C" means continuous voltage control, the "T" means tapped voltage control. So my machine only has the several fixed voltage settings, with the "C" machine you should be able to tweak the voltage more accurately. On a couple occasions I'd like to have had the fine control.

-brino

I've got a Red one and Blue one, so I don't get into the color debate either. I think the choice in a hobby setting is more to do with the type of welding projects you want to do with it. If you want to build trailers, the machine would be different than if you wanted an occasional small project out of 16g sheet goods, or you wanted to do mostly aluminum.
I've got a pretty old 35S (blue) that I keep set up for stainless, and a 300 CV (red) that I keep for carbon steel. Alum gets another machine. I don't do much in the way of big fab work any more, so they are more luxury than need. If I had to choose......well I'm glad I don't!

Well, in actuality, the red one is 3 phase, and the blue one is single. I have extensions for both, so the choice is still what I want to weld. For the majority, by far, I use the Lincoln, simply because it is carbon steels that I weld most of. It's nice having the options without swapping bottles and rollers, and wire......etc..

JR49 said:

I have been reading some of the posts in this welding section, and one thing has come up a few times that confuses me (doesn't take much). You guys talk about using so many "amps" and a certian "wire feed speed". Now I have an old sears AC buzz box, that I've been using for years for my own bubble gum welds, and my knowledge consists of this "thicker steel means more amps and bigger dia. stick electrodes. Burn through-- lower amps" My son has a little Lincoln 125 plus mig welder with argon/co2 bottle that he uses for thin steel, and the only controls on it are VOLTS and WIRE FEED. Where do the amps (heat) come in? And if I'm burning holes, what do I turn down, or, in the opposite situation, (not hot enough) what do I adjust? Thanks, JR49

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I think you will find some very useful welding information on a site called, www.welding tips and tricks.com