Rookie in need of help

[CDUB67]

Hi All. Happy new year to everyone.

I posted for the first time in November and you were very helpful. Hopefully you can help me again. I’m new to welding and am slowly getting better at it but I’m having a problem with either my welder or my technique.

I have a second-hand Millermatic 175 and am using solid .24 wire. All parts/accessories are clean and in good working order. I’m trying to plug weld drilled out spot weld holes in clean and prepped 20-gauge sheet metal. My C-25 gas is set at 17 and my voltage/wire speed at 1/40 (the chart on my machine only goes to 18 gauge and calls for 1.5/40).

When I pull the trigger, I get a couple of seconds of good, bacon sizzle welding but then it shifts to a sound like a bottle rocket taking off causing it to “flare” and burn through (or, in this case, melt the edges of the holes).

I’m not convinced the voltage/wire speed has anything to do with it as this consistently happens no matter what they’re set at (but I certainly could be wrong). I’m wondering if there’s a problem with how the gas is being dispensed.

Hopefully this makes sense. Any help will be greatly appreciated.

[Bushytails]

A regulator with an actual flow meter (the kind with a ball in a tube) can help with diagnosing gas flow issues, if you think you're having them. However, the first thing I'd do is try different settings of gas flow, wire speed, and voltage, and see if you find something that works better. Charts are starting points, not the final answer.

[walker]

What he said, plus, post a picture of the problematic weld.

[MMW]

Are you sure it is bare steel and not coated, galvanized or plated? Maybe you are holding it to long and it is burning all the way through then sucking in contaminants from the back side? Especially if back side is painted/coated with something. Have you tried doing a lap weld on some scrap of same metal/thickness? What were those results? Are you indoors with no wind or fans? Initially when you pull the trigger you get a "rush of gas" then after a second it will settle in to steady flow, have you checked that you hear the gas consistantly, have you tried upping the gas flow to 25? All gas connections tight and not leaking? Does the gun plug into the machine, if so are the o-rings there, in good shape? Diffuser holes by tip clear, nozzle clean?

[CDUB67]

Thanks for your input. The picture is of a practice run I did earlier today. Bare 20-gauge sheet metal. I might be holding it in place too long. The metal I’m working has been cleaned of rust and paint, I did put weld-through primer on it.

I checked everything MMW asked: the nozzle, tip and diffuser are all recently replaced and clean; O-rings are fine; I’m indoors with no wind or fans; all connections are tight; no leaks; I increased the gas to 25 and reduced the wire speed to 30, both of which seem to have helped some but it’s still “flaring”.

Gas is coming out of the nozzle all the time, even when I’m not pulling the trigger, which I never noticed before. Is it supposed to? I’m also noticing that sometimes there’s no wire feed when I pull the trigger and I have to click it once or twice before it does feed. The wire guide/roller is correct size and in good order, and the tension seems to be appropriate (I tested it without the gas open and it fed perfectly).

[Aeronca41]

Gas should only be flowing when you pull the trigger; sounds like you have gas flowing as long as the welder is turned on? That's going to get expensive! Try unplugging the small cable that plugs into the front of the welder from the gun and see if the gas stops. If it does, you have a problem with the gun; if not, there's a problem in the welder. The intermittent wire feed might well be due to problem with the gun also. You should not have to press the trigger more than once. I'm suspecting a bad gun.

[CDUB67]

Thanks. I was just reading on another site about a similar problem on a Hobart and suspected as much. Your tip will be helpful in attempting to diagnose.