welder problem

[jasonb]

I've got a Millermatic 175.. about 1.5 yrs old but not really used much. So I'm plating the side of my Samurai's frame so the spring hangers don't rip it apart one day. Anyway, I'm just tacking the plate into place and the wire keeps burning inside the welder and stopping the wire from moving obviously. I haven't changed anything on the welder or the way I'm doing anything. New tip and clean nozzle. It's .30 wire with the Ar/CO2 gas. Here's a pic of where it keeps cooking as soon as I get a tack. It will feed but if I contact the metal, it makes a quick tack and that's it before the wire melts inside, basically where the little spring piece is.
Also, a pic of what I'm welding in case you see something crazy going on that I don't. I tacked on a piece to the plate to attach the ground clamp, and used C clamps to hold the piece to the frame.

[beaker]

I'm pulling this partially out of my ass, but it looks like somehow there's current going from the ground clamp through the chassis of the welder to the wire, to the metal of the gun cable...

Is the welder itself, the cart its on, or the tank touching the Sami?

Inside the cabinet, where the ground lead is attached to the post, is there any debris, loose copper coming from the crimped connector, chafed insulation?

Where the ground cable leaves the welder's case, is the ground cable's insulation in good condition??

[PAToyota]

I think Beaker is on the right track. It seems like something is grounding within the welder and shorting out.

[jasonb]

Is the welder itself, the cart its on, or the tank touching the Sami?

Nothing is touching the Sami other than the actual ground clam. I'll get answers to the other questions. I'll get down there tonight and see if I can locate anything grounding to the welder. Thanks for the suggestions.

[j.kimball]

sounds like your liner is bad that the wire feeds through, the only current that wire should see is at the contact tip. if it is burning inside as it feeds through there is a hole in the teflon lining inside the feed for the gun.

[jasonb]

well I took the gun apart and cleaned out as good as I could. Put a new tip on. Checked all lines that I could for bad spots and everything looked good. I put it all back together and it seems to be working fine now. Hopefully that's all it needed and the lining is OK, but we'll see. Thanks for the tips. Guess I'll go see if I can find a liner just in case.

[j.kimball]

sometimes i find i will get a piece of slag stuck up inside the nozzle that will connect the liner to the nozzle and cause the same thing you experienced. i got a tub of nozzle dip from the welding supply shop and have not had the same problem since. glad you got it working.

[jasonb]

yeah I have the nozzle dip stuff... I just always forget to use it. Guess this is my lesson!

[chumly2071]

looks like you might want to also blow the cabinet of the welder out with compressed air. there appears to be a lot of metal dust in there. may not be your problem with the burn back, but certainly couldn't hurt.

[Static-XJ]

I had a wire burning at the drive wheels once, turned out the wire spool (was a metal one, not plastic) was out of round and contacted the inside of the welder, arcing as it did so.