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 Post subject: Burn back
PostPosted: July 7, 2012, 1:01 pm 
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Joined: October 11, 2006, 4:11 pm
Posts: 125
Location: Abbotsford B.C. Canada
Hey all, I'm having a problem with my welder... or more likely my welder has a problem with me, I have a baby Lincoln which came in a mig pack 10 box about 5-6 years ago, perhaps 120 amp? In the time that I've owned it I've converted it over to gas and am using a flow meter at about 10cfm with my welds (tri mix gas) and until recently it has been as reliable as a brick. Now I'm having a problem with the wire (.35) burning back to the contact tip. I should mention that the first few welds that the machine does when cold are normal, after that I fight it. I'm noticing that rather than a normal contact puddle and the usual buzz I'm basically seeing an arc going across from my tip to the work surface accompanied by a hissing sound. When it does decide to weld it's painfully messy and there are splatters and pops everywhere, I ruined a shirt and burned a couple holes in my jeans yesterday.
I suspect that this is a simple problem but being a self taught welder perhaps I don't have the resources to fall back on.

Thanks guys,

Ted

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 Post subject: Re: Burn back
PostPosted: July 7, 2012, 1:23 pm 
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Joined: July 2, 2010, 1:13 am
Posts: 431
Location: Phoenix arizona
Thicker wire requires more amps to melt it,and in turn more wire speed,the wire you are using is your problem because your small machine doesnt have the power to keep it melting,switch to .23 and your problems will go away.


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 Post subject: Re: Burn back
PostPosted: July 7, 2012, 1:27 pm 
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Joined: October 11, 2006, 4:11 pm
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Location: Abbotsford B.C. Canada
Oh... Good thinking! I'll try that.

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 Post subject: Re: Burn back
PostPosted: July 7, 2012, 9:29 pm 
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Joined: November 7, 2009, 8:28 pm
Posts: 15
Is the wire feeding cleanly, or is going in fits and starts?

A couple of things to look at:

Is your contact tip worn? The brass piece in the gun that the wire fits through needs to be a good fit on the wire. If it's loose, the wire won't carry the current to the work.

Have you checked your feed rollers? They might be slipping on the wire.

Is your cable sheath kinked anywhere? Try stretching the cable between the welder and the gun out straight before you weld.


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 Post subject: Re: Burn back
PostPosted: July 7, 2012, 10:01 pm 
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Joined: January 10, 2008, 4:47 pm
Posts: 7654
Location: Massachusetts
You use different tips with different sizes of wire right?

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 Post subject: Re: Burn back
PostPosted: July 12, 2012, 6:58 pm 
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Joined: September 27, 2010, 8:21 am
Posts: 32
Location: Memphis
I know I don't post a lot because i'm here to try and learn more than I'm here to teach (and I don't care to argue over the internet).

However this is something I might be able to help in as I know quite a bit about the subject at hand.

It does 'sound' like you have a wire feed problem, however with the spatter it could be that you are out of gas, if your willing to waste some wire pull the trigger and watch about a foot and a half come out. It should move smooth and you shouldn't feel any jerks, bumps, catches, kicks or anything else from the handle. If its not all smooth you should change the contact tip(touches the wire) and clean the feed wheel and check for rust on it where the wire runs.

Next check your bottle pressure, and hold a string out in front of your tip and pull the trigger to see if the gas is actually making it to the tip. Another indicator of bad flow is a lot of carbon around the arc area.

A side note to help prevent flow problems is to clear the bottle connection before you hook it up. Crack the bottle open as wide as you can and back shut in about half a second(total time) DON'T DO THIS WITH ACETYLENE EVER and make sure there are not open flames or heat sources anywhere around for other flammable gasses.

It doesn't sound like your wire is to thick, both because you didn't have this problem before and you said the rod is melting back to the tip. If its to thick or more accurately if you can't get it hot enough, you will experience the rod hitting the surface and 'pushing' the stinger(welding lead) back away from the material. If you do experience this, and the wire size hasn't changed, go ahead and check your contact for your ground and then just go ahead and replace the tip if the ground isn't the problem.

A lead could be kinked and you might not know it from the outside of it.. it could also just be worn out. As long as you wind up/store/hang your lead in the biggest loops possible to get it where you want it than you should be ok, and always try to keep it as strait as possible when using it.

I know some of this stuff was pointed out already, I was just trying to expand on it.

And yes different size wire means different sized contact tip.

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