How do you teach people to set MIG machines?

Perhaps you could try and refine an anology that show it as a set of ratios. Heat/travel speed/wire speed/material thickness. That's the way I have to think about it.

Then some.

Trouble / Solution examples.

Tell them to start with the chart inside the door of their MIG machine. Then show them what it looks like when the wire speed is too low, then too high, then what it sounds like and looks like when the voltage is too high.

It depends a lot on whether you're only teaching short-circuit or if you're also teaching globular transfer and spray mode.

Grant

When you figure it out, you can teach me. :)

Setting MIG parameters has to be the most odd and complex things to try and do in welding. There never will be a good way to teach it if you ask me. :)

As was already said, the place to start is with with chart inside the machine, or a similar chart from a book if you are using a machine without a chart. But them you need to deal with the complexity of units on the settings (ips vs amps, or all the machines which don't have any units other than 0-10 or A, B, C, D settings).

One way I heard it described was that the voltage is adjusted to control the height of the bead. If you set it to high, the weld bead will be flat, and you will get too much splatter. If you set it too low, the bead will will stand up too high (look cold). So the idea is to fine tune the voltage to get the correct shape of weld bead.

The wire speed should be thought of as working like the amperage control for the other welding processes. The faster the wire moves, the more current the machine must use to melt it, and the more heat you end up putting into the weld. So if you are getting too much penetration and burning through your work piece, you must turn down the wire speed. And if you are not getting enough penetration and heat, you must turn up the wire speed.

The two controls of course interact with each other to make it all more complex. If you increase the wire speed, you have to increase the voltage to keep an optimal weld setting.

For short circuit transfer, the rate of buzzing is the factor to listen for and set. You turn up the wire speed to increase the rate and turn it down to decrease the rate.

Yes, but .. what I look for is if the bead is real tall, there isn't enough heat, so turn up the wire speed. And if I start getting excessive spatter then I turn down the wire speed. What really gets me is when the wire speed is too low or the voltage too high and I go into globular transfer mode with its characteristic "pfft" sound. Can't describe it, but when I see it, I immediately turn down the volts some or turn up the wire speed.

Yes, you need to think of wire speed as amps.

Also it's really helpful to show them a welder with a real old gun liner to show them the kind of wack problems that show up. Ditto for worn out contact tips.

The hardest thing to teach about MIG, though, is how to see past that bigass nozzle. Also, to keep your stickout low. Turn up the amps for an inside fillet, turn down the amps for an outside corner. There are also lots of tricks to seeing the seam.

You can get someone welding MIG in about 20 minutes. To get them confident they can handle about anything takes, um, longer.

Grant

Good description of the situation! I am currently learning MIG after 18 years of TIG. It's a different beast all right.

BobH

Care to share some of these tricks? I find it very difficult to look past that 'bigass nozzle'.

-- As Iron Sharpens Iron, So One Man Sharpens Another. Proverbs 27:17

Thanks for the good replies!

We start the students on .035 solid wire (steel), short-circuiting with C-25 (75/25) gas. We don't introduce other wire types or transfer modes until the second semester.

I am primarily a TIG welder, but I have spent enough time with MIG that I don't have trouble with making the machine do what I want. I just pretty much know about where I want the settings depending on what I am welding, but getting the students to that point is another matter!

I have tried teaching the theory out welding textbooks: amp/volt curves and all that, but that doesn't help.

Recently, I have been wondering about putting together some kind of excercise that will help students really gain an understanding of the wire and voltage controls. Any thoughts on this? Any suggestions? Thanks much!

Matthew.

Usually, there is a chart on the inside of the door. That always works pretty good.

Steve

You are all correct here, but what I do not see being addressed is motion. A machine can be set at the right settings, but the bead appear too high or too low depending on movement of the puddle. It can also be affected if you are pulling or pushing the wire.

A lot of MIG can be done with just a push or drag motion, as with ornamental metal. In that case, a straight bead is sufficient. But when there is a root or a joint, there needs to be the proper amount and type of motion to move the puddle around and melt the adjoining metals. Straight beads may be acceptable in successive rows, but many times there is a need to tie things together, and a zig zag or weave is needed. In that case, a puddle that is flat and capable of being targeted specifically to one spot is needed.

What is needed in those cases is a thorough understanding of the proper sequence of welds for any joint, any position, and any direction of weld.

HTH

Steve

One exercise we were given was to run multiple beads on a plate side by side changing one paramater each time. So you would start with what should have been correct voltage, wire speed, and travel speed, then try setting the voltage way high to see what would happen for the next bead. Then set it way low, then return the voltage to normal and run beads with the wire speed way low and way too high. Then change the travel speed to too fast, and too slow.

That was an ok thing to try, but mostly, all it showed me was that a very wide range of parameters would still produce a basic weld and that adjusting the travel speed would basically adjust for the other parameters. So when you turn the wire speed up, you have to travel a little faster to make up for it etc. It didn't really do much to show me what was right, but it did give me a little more feel for what the adjustments did.

One of the text books we used did have a series of time consuming exercises to get people familiar with the parameters. We didn't do them, and I don't remember the details exactly, but it was something like a science experiment where you would make many welds on the same material trying to keep the travel speed constant while slowly changing voltage and wire speed for each weld and recording the results of bead shape and penetration. The goal was to end up with a chart of many different voltage and wire speed settings along with weld quality that should show that only the right combinations of wire speed and voltage would produce to best welds.

But all this is kinda hard for someone new who is trying to learn to weld in general at the same time they are trying to figure out how to set the parameters while also controlling travel speed, and stick-out, and work angle.

One thing we couldn't do very well at our school was adjust the parameters while running a bead. The equipment just wasn't located in a way to make that very easy to do. It was mostly a problem of picking a setting, and then trying a weld, then changing the setting, and trying another weld. This is something I'm going to spend some more time experimenting with now that I have my own MIG machine and can set it up within reach so I can do more adjusting while welding to get a more instant feedback on how things change as I play with the controls.

If you have equipment set up in the lab that makes that possible, it might be something you would encourage the students to try. Or maybe even have one student changing the controls while another student runs beads on scrap material.

The engineer in me would like to have an automated system to move the mig gun at a constant speed and hold it at a constant distance from the work so I could spend a few days testing for myself in a controlled environment how all the parameters interacted with each other. A set up like that might be an interesting teaching tool where the student could adjust the dials to control voltage, wire speed, and gun travel speed to see how the weld changed. When you have a person moving the gun, you get another uncontrolled variable.

Still learning to weld with a real welding machine I have found the chart to be useful, but not perfect. It would be really useful to see some good welds and bad welds side by side with a simple...

Increase wire speed

Decrease power

Etc next to each of the bad welding mess ups like bad spatter, burn through, tall bead, etc.

So whatcha waiting for? Get busy! Or don't you feel competent to do bad welds correctly? :-)

Grant

I'm perfectly competent to make bad welds. Thank you very much. :^(

Yeah, just a starting point. Like flat position. But who welds flat position on plate with MIG? As I said in another previous post, from the basic, there are a lot of changes due to position (flat, horizontal, vertical, overhead) torch angles, push/pull, and other stuff.

Steve

Thanks to all for the replies!

Matthew