Kevin starts by saying there’s no easy answer for how to get the right settings, but through trial and error, some basics, some tips and tricks, and some practice, you can get to the sweet spot you are seeking.
Kevin uses his Miller 251 MIG welder because it has a handy chart right inside the welder’s lid. It shows you the different kinds of material you might be using – steel, stainless aluminum (if you have a spool gun) – and the suggested types of wire, which can really be a big help. The chart also provides a suggested flow rate for the gas and what kind of gas – straight argon, CO2, mix, etc. – you are using. It also suggests which wire size and finally, the thicknesses of metal with suggestions for voltage and wire feed.
For his demo, Kevin is using 1/4″ mild steel, so he checks the chart. Knowing that he’s running .030 steel wire as well as mix gas (75% argon, 25% CO2), he sees he should start at about 19.6 volts and 435 wire feed. Now that he knows where to start, he can go to his bench, set up a test piece, and practice and fine-tune from there.
At the bench, Kevin has the piece of 1/4″ steel clamped to the bench. As suggested by the chart, he has the machine set at 19.6 volts and 435 wire feed. If you’re just turning on your welder for the first time that day, he reminds viewers to bleed the gas a little to get gas all the way to the end of the torch.
Then Kevin runs a quick test weld. He shows the weld, calling it a little cold because the weld is high and humped, whereas it should be a little flatter and wider. It also could be a little too much wire feed, depending upon the gap between the two pieces of steel and the penetration you are getting, but you can also control that with voltage. So you can turn down the wire feed or turn up the voltage and leave the wire feed as is, working with them to get the same effect – as long as you are getting penetration. He decides to turn up the voltage to 20.6.
Why aren’t the suggested settings perfect every time? Kevin emphasizes that they are just suggestions for getting started, but there are other variables that can influence the settings. For example, he’s welding on top of a 1″ thick steel plate, which is sucking the heat out of the piece he’s welding. So that probably means he’ll need a little more voltage because of the table acting like a big heat sink. Also, what position are you welding in? Horizontal? Vertical? Overhead? Those conditions are also going to change the settings a little. Kevin says that’s where practice comes in.
He turns up the voltage and runs another bead. When he shows the welds, the second weld is wider but it still has a hump, so maybe less wire feed or slower travel speed might help.
Then he flips over the piece of metal. Because he intentionally left a 1/16″ gap between the two pieces of steel, you can clearly see the penetration. The first run at 19.6 volts got pentration all the way through to the surface of the other side. Interestingly enough, the 20.6 weld did not, something Kevin says requires more practice and more learning to understand better.
In general, Kevin says it’s worthwhile to take the time to figure out the right settings for you, your location, your project, your machine, etc. He highly recommends going to the Miller site and finding the chart or you can use Miller’s calculators. You also should keep some metal scraps around, preferably in the same gauge as the metal you’re welding on, so you can practice and getting your settings just right before you begin welding.