What would make a MIG liner do this?

admin

One of our machines stopped feeding last night. No erratic behavior, one minute its fine, then it just stopped. Pulled everything apart and found this. We are not running this wire (Dual shield 1/16 309) anywhere near the top of the heat range and I think this is a 300 amp gun. The liner was warm, but the plastic coating was intact, hadn't melted.It was twisted up so bad that the wire was stuck in it.Any ideas? I put my last liner in to replace it, but I don't wanna lose this liner tomorrow night at 11pm and have a machine down. Attached ImagesLast edited by Burnit; 12-03-2008 at 06:08 AM.Yup
Reply:Never seen a liner go that bad before. Only thing I can think of is constantly turning the gun around which would be imposable......Mike
Reply:Originally Posted by mrmikeyNever seen a liner go that bad before. Only thing I can think of is constantly turning the gun around which would be imposable......Mike
Reply:I'm thinking along the lines of twisting the gun up.  If that's the case it appears you've got a temp that's not very interested in becoming permanent.MM200 w/Spoolmatic 1Syncrowave 180SDBobcat 225G Plus - LP/NGMUTT Suitcase WirefeederWC-1S/Spoolmatic 1HF-251D-1PakMaster 100XL '68 Red Face Code #6633 projectStar Jet 21-110Save Second Base!
Reply:The twisting was what I was going to say as well.  Looks like a lot of extension cords I have sceen at peoples houses that never take the time to put them away right.  Kind of hard to tell from the pic though if it is twisted or just wavy.  Also might have had been the wire getting stuck and bunching, but I have never seen wire do that to a liner.  Then again I have never used dual shield.Last edited by Martygras; 12-03-2008 at 10:17 AM.
Reply:I think the drive rolls were to tight and got the wire cork screwing starting into the liner so the linner started cork screwing too.
Reply:From the looks of it, the wire was under tension while the liner was under compression.You know what happens when you kink your whip the wrong way or the drive rollers slip for some reason. The wire burns back and it sticks to the tip. Happens to everyone occasionally. If one tried to unscrew and yank the tip out with a pair of pliers while holding the gun  without releasing tension on the rollers (or jogging the drive a couple times) that's exactly what a plastic liner might end up looking like. You can't do it with a *heavy duty* gun like a 400amp Tweco because the liner is a coiled metal housing (like a bicycle or PTO cable housing) and it won't compress at all. I know some of the medium duty guns just use a plastic tube, which is easier to damage if you abuse it.Extension cords sometimes look the same way some times because non-electrician people tend to stretch the cord to straighten kinks when rolling them up. The stretched outer insulation slides along the inner conductors (which are not as stretchy) and  bunches up near the ends where the plugs stop it from sliding along any further.-Matt------------------------------------------
Reply:Observe the guy who was working with that welder while he works.  Much might be learned from focused and patient observation.-MondoMember, AWSLincoln ProMIG 140Lincoln AC TombstoneCraftsman Lathe 12 x 24 c1935Atlas MFC Horizontal MillCraftsman Commercial Lathe 12 x 36 c1970- - - I'll just keep on keepin' on.
Reply:My guess would be that the liner somehow carried welding current, which overheated and annealed the liner's wound wire core.
Reply:Originally Posted by denrepMy guess would be that the liner somehow carried welding current, which overheated and annealed the liner's wound wire core.
Reply:I'm serious. Normally, the liner is electrically isolated; current flow should be from contact tip, to wire, to work.My guess is that somehow the liner carried high current, which warmed the liner's wound wire wall, causing it to deform.Burnit should skin back the cover and look for evidence of overheating; such as discoloration of the core.Last edited by denrep; 12-03-2008 at 05:52 PM.
Reply:Looks like the last guy that changed it drove it in with a hammer or didn't trim it to length.OR there is a poor connection some where.Its sure gonna weld better with a new one.David Real world weldin.  When I grow up I want to be a tig weldor.
Reply:Originally Posted by denrepMy guess would be that the liner somehow carried welding current, which overheated and annealed the liner's wound wire core.
Reply:Originally Posted by OMS ...not sure how the cable that carries the welding current can short to the liner without massive trauma, but I guess anything is possible....
Reply:Originally Posted by denrepShort circuit current path could have started outside of the liner; maybe at the drive rolls or at the electrode reel hub.
Reply:My first gut instinct was that you were over working the guns amperage rating.   But seeing as you claim otherwise im thinking that who ever changed the liner last wasn't a real sharp operator and ended up just stuffing the liner in there with wreckless abandon at all costs instead of doing what's supposed to be done and trimming to fit.I have seen PHENOMINAL welders that couldn't change a set of drive rolls so this can happen.   Some places like shipyards will fire a welder if they see him doing anything but changing the roll of wire on his feeder.  Anything more than that and they have to take it to the tool crib.Vantage 500's LN-25's, VI-400's, cobramatics, Miller migs, synch 350 LX, Powcon inverters, XMT's, 250 Ton Acurrpress 12' brake, 1/4" 10' Atlantic shear,Koikie plasma table W/ esab plasmas. marvel & hyd-mech saws, pirrana & metal muncher punches.
Reply:First thing I see ,,,,,,,   many people have found out, installing a new liner, to shorten/lengthen it a half inch, you can twist the gun cable one way or another, just watch the liner recede or come back out.  When you do this, obviously, you are simply twisting the liner, either longer or shorter, depending on which way you rotate.   Add a little time and heat,,,,   you see the result.
Reply:It does look like it twisted.  I don't ever do anything that will keep the liner from spinning at the feed rollers.  As for the liner carrying current...  I don't think you will get a teflon liner to carry current sufficient to melt it or even soften it.If you can tell looking at it that it's a result of heat, you could just get a metal liner.  Word to the wise:  Get wire lubricant and one of the felt pieces that lubricates it.  At the start of each shift, soak down the felt piece.  This cleans the wire and lubricates the liner.  It will help improve the life of a liner, and the smoothness of wirefeed.
Reply:Well Burnit... What'd the autopsy show?
Reply:Originally Posted by EngloidAs for the liner carrying current...  I don't think you will get a teflon liner to carry current sufficient to melt it or even soften it.If you can tell looking at it that it's a result of heat, you could just get a metal liner.
Reply:Can't see it being too long doing it, you'd never get enough tension on it, at least I don't see how you would. Got me stumped....Mike
Reply:Originally Posted by Burnit1)These guys have really been cranking on the drive roller tension, in one instance he somehow shorted the wire to the tip, fusing them together, then came and got me when it wouldn't feed anymore. The drive roll tension was too high and when I managed to get the wire out of the liner (Vise-Grips) there were two flat spots on the wire from the rollers that had made it into the liner. Its a long shot, but I weigh 240 lbs. and it was hard to pull that wire out, even from the feeder end. The feeder managed to force that in there, maybe that could have done it.