Problems with MIG field welding of 18 ga s/s round/square duct

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I have been encountering numerous problems on a daily basis – welding square and round duct, most of it hanging in the air/not movable, in the vertical and horizontal position. I am using a small miller 110 unit, running .030 wire. There have been lost of mistakes, and we have had to plasma sections, and the re-weld them. sometimes, because of butting irregular cuts, I’ve had to fill open gaps of 1/4″ or more. On the side or bottom of 16″ round duct, this can be a real problem. I just try to bridge the gap, then quick trigger the gun, allowing the just deposited puddle to barely cool before I deposit another puddle to continue the weld. This is a slow process, and many times, either side of the gaped butt weld melts away – leaving a wider gap. Gravity helps me on the sides, but the overhead or bottom 1/4 of the weld is very difficult. I tend to get big blobs that hang down.Even after considerable grinding – the weld looks lousy – even if it is air-tight.Is there some technique I might use, gun angle, travel direction ? Or is this an impossibility? My other almost daily challenge is trying to join 2 joints of rectangular duct together by welding 2 butted 1/2″ 90 outside flanges. Rather than a nice smooth, continuous little bead, I tend to get alternating irregular areas across the length of the seam. Compounding my problems is the fact that many trades are using the same power boxes I use, and the power source can fluctuate. Do you have suggestions ( I can’t get a line designated just for my welder). Should I give up the welding and become an electrician ? I would appreciate any useful advice. I don’t know if I can maintain my sanity if I have to do this for 3 or 4 more months.

Thanks – Marc, Ventura-Ca

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