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This is how I was taught to set those up. If you try this be sure you are not grounded because the wire will be hot when you squeeze that gun trigger. Some are hot all the time so be careful. Tighten the drive rolls until you can hold the wire between your fingers and the drivers keep pushing, forming a loop in the wire between your fingers and the contact tip. If the wire slips while you are holding it, the drivers are not tight enough. There may be other drive roll configurations for your machine also. For tubular wires, a U-groove roller is recommended. Knurled for extremely soft and V for hard wires. Cast and helix are also going to be a factor. If the cast and helix are not controlled by the manufacturer the wire may have too much memory leading to feeding problems and premature drive component wear. Some of these manufacturers draw wire so hard or so dry that if you look at it under a microscope it has little flakes and burrs visible. Some don't get all the lubricant off either. Once while consulting a drawing mill in regard to extending part life, I had one wire mill supervisor tell me "We don't make the best, we make the most." It was quite obvious. Burn back can result from a trimmer pot that needs adjustment. Especially if you experience it upon starting the arc. It can also be an indication of incorrect arc voltage. Arc length effects that for one thing. Probably should suspect drive line components first. Like T-bone said, be sure everything is lined up with the drive rolls. I've had brand new Miller machines that we had to work on right out of the box.
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