mig welder help needed

[oj]

Hi all,

i"ve got a Lincoln 255 mig welder, had it for about 10 years now, and i"m self taught welding wise, never been to school for that at all. My big problem lately is the wire burning back to the contact tip when starting to weld, once the arc is established, everything seems good, makes a nice "crackling" sound, and the welds seem to be strong, (most of what i"ve welded hasn"t broken -yet).

We had to change the gun a year or two ago (ran over it with a tractor) so it had a new liner with the gun, i don"t use the welder commercially, just for fixing stuff on the farm (grapple on the loader this morning!) so it doesn"t get a lot of work. I"m using plain steel wire (not the copper covered stuff), but the welder is in a heated shop (about 55 -60 F).

Anyone got any ideas?? "operator error" springs to mind, but i"m not sure what i"m doing wrong...
Thanks.

 

[Puddles]

oj the first thing I would do is turn up the wire speed a touch, or turn down the voltage.

Next thing would be to blow the gun out; I like to use my oxygen bottle with no gauge on it. Be sure to remove the contact tip first. 2,000 + psi will clean it out fast.

You are making sure the gun is straight as possible?

Your not using one of those little felt pads on the wire are you? If so, don’t!

 

[oj]

Thanks Puddles,

I'd thought about using one of those felt pads, not used one yet... now maybe i wont bother to try one!

I'll try the gun cleaning idea, as most of the time the gun cable is straight ish, well as straight as machinery designers will left you hold it!

Read my manual (for the second time in 10 or so years) would wire run in speed make a big difference? not sure how my machine is set right now, but book says 2 speeds are available, wire run in as set by wire speed control and a slower speed (50 inches/hour i think) accelerating to wire speed control setting upon striking of arc...

 

[Stan in Oly, WA]

Hi Puddles,

Why don't you think using one of those wiper pads is a good idea? (Don't tell me that it has to do with welding while you're standing in water up to your knees---you've already used that one.) They seem like a good idea to wipe airborne shop crud off the wire to keep it from going into the liner. What am I not seeing about this?

All the best, Stan

 

[Anonymous-0]

Your new gun and liner may be sized for wires bigger than the last. Causing some delay in the time that it takes this slop to be filled by the wire before the travel at the tip starts.

 

[Puddles]

If anything just use an earplug, never ever use a felt pad with that liquid on it. Even Lincoln does not recommend the felt pads.

I’ve only heard of “Wire Run in Speed” never used a machine with it. I’m strictly old school, :lol: I keep things simple. :wink:
I have a Cobramatic that I use for aluminum, I have to crowd, (seems like too much) the wire speed or it will burn back to the contact tip in a New York second.
If your adjustments aren’t off, I think you have a drive system problem, as in the wire is not flowing smoothly some way or another. Maybe as simple as your drive roll tension needs to be tightened, wrong drive rolls, could be just about anything.

 

[Puddles]

Stan it’s just another thing to contend with. If anything just use an earplug. Back in the day I would run 70-pounds a wire a day, 5, 6, 7 days a week. Now when I say wire I mean Innershield. Innershield has a graphite lube on it. That lube is a mess, and along with the little metal shavings caused by the serrated drive rolls, this all adds up to a nightmare for the Lincoln guns, that do not have a replaceable liner. I never used a felt pad, what I did, and made sure everybody working for me would do was to blow the guns out with an oxygen bottle at the end of the week. Those Lincoln guns are about $250.00 each! Taking couple minutes each week to remove the gun and blow it out is money well spent if you ask me. Bottom line the felt pads do no good for the metal shavings, no place to install them between the drive rolls and the feed tube going into the gun. Back on the wire before entering the guide tube is fine, just don’t use the ones with lube on them! :wink:

 

[Bspauld]

make sure you have the right clearance from the cone to the tip,if its to short it can cause the wire to burn to the tip

 

[MarkB_MI]

Is it possible the polarity is reversed? You need electrode positive for gas, electrode negative for flux-core.

 

[Crem]

Probably a dumb question but have you changed the contact tip lately? Sometimes that helps.

 

[Doug - Iowa]

All the other advice is good but I didnt see anyone mention corrosion on the wire. When my MIG was acting up same way last fall, I ran out a good amount of wire to see if there was a problem with it. Sure enough, it had rust spots on it every couple feet or so. Upon close inspection of the spool, apparently a mouse had p!ssed on the spool and caused a spot of corrosion about the size of a quarter (found evidence of mouse nest inside rest of welder as well). Every round that the wire came from that spot the MIG would stick. Replaced the spool of wire and no more sticking. Oh - and put a package of mouse dope in the bottom of the welder too.

 

[JMOR]

I would certainly look into feed tube and even try different (new) wire before going real deep, but just so you know, I ran into a feed problem on a Lincoln SP-130T that we had used successfully for 10 years, then not. After much work, experimenting, substituting, etc., I contacted the factory & because of all the detail I was able to provide, they kicked me up to engineering (a rare move) and after several exchanges, they told me about a problem with their feed motor drive circuit board and that it was solved by a new board design so time during the production run. He supplied me with the schematics and I built a new board for mine & fixed the problem.
A major clue to this being the problem is that it will feed fine on the lowest two power settings, but will not work correctly at the higher settings.

The big question still remains, is why did it ever work over all those first years?

 

[Bodyman]

OJ, I would replace your contact tip (if it is worn even a small amount it can create a drag that might cause the wire to drag just enough to burn back and stick) also I would suggest checking the tension on your wire spool and maybe loosen it a little. You most likely would have mentioned this, but my Lincoln has a specific burnback adjustment, had to mention it.

 

[Crem]

I just thought of a problem that I saw quite often at work. Is your ground clamp in good shape? Also check where the cable is attached to the clamp and at the other end where it is plugged in. If you have it bolted to your bench check that connection. Bad grounding can cause arc starting problems as it also arcs at the bad spot. It may start making good contact as you weld and then the welding will be normal.

 

[Anonymous-0]

The graphite on Innershield is supposed to stop corrosion and make feeding easier. It is a mess. The felt pads with the wire lube are OK for solid wire if the drive rolls aren't too tight. A lot people have feeding problems from a bad contact tip or liner, etc. and to compensate they crank the drive roll pressure too high which causes the wire to flake off and plug the liner. Properly adjusted, the wire should slip before it birdnests. Of course with .023 wire, it can be a problem with everything perfect. Dave

 

[trucker40]

If you change the wire,like you say its plain steel instead of copper colored,do you mean its flux core wire?Anyway on the spool it should say what size the wire is.You have to have a tip for that size wire.If you switched from solid copper covered wire to flux core you probably need a bigger tip.I was having trouble like that but I never use flux core wire,and mentioned it to my supplier and he said to try the next size bigger tip after blowing the liner out.I did that and it works good.Also you can take a torch tip cleaner thats like a drill bit and clean it out and it might fix it too.Now if you drop something on the cable it could mess up the liner.Also you want to have it out as straight as you can get it.Its hard to push the wire if you have it coiled up and try to weld.
I was using mine to weld aluminum before and its hard to push aluminum up a 12 foot liner and i tightened the drive rollers down and it peeled flakes off of the wire and it got the wire jammed in the liner.The thing to do might be pull the liner out if you dont see anything obviously wrong and while its out blow it out good with compressed air.Put it all back in and check the guide where the wire goes into the liner and as you put the wire in check and see by stopping and try to pull it back a little and see if it gets tight.As long as it goes through the liner and tip good it should work.Also you might look at your wire speed and see if its too slow.If your wire is rusty you can get a felt thing to clamp on it and spray it with WD40 and it helps for that.

 

[Anonymous-0]

I used to have a Lincoln 255. Wire run in speed doesn't affect stopping the weld. I really liked the slower wire run in speed because it feeds the wire at about half speed for the first second you pull the trigger. It elimates cold starts and having bits of MIG wire on the start of all your welds. I've seen this a lot of different pieces of equipment. My deluxe Miller wire feeder also had slow wire run in. It's a great feature to have. You could check the wire guides before and after the drive rolls. I've seen them plugged up. First thing to try is a new contact tip though. Dave

 

[Anonymous-0]

Solid MIG wire comes in plain and the more common copper coated form. Some people prefer the plain wire because there is no copper to flake off, but it will rust easier. Contact tips are pretty cheap so if in doubt, it's better to just replace them. Trying to push aluminum wire is like trying to push a piece of string. Tightened the drive rolls on any wire will deform the wire and make things even worse, including wearing out the grooves in the drive rolls and deforming the wire enough to cause feeding problems through the contact tip. Aluminum wire in a standard MIG gun has about a 1% chance of "almost" working and a 110% chance of creating new curse words! 12 feet, forget it! I don't think WD40 is made as MIG wire lubricant. There is special lubricant though. You don't want to add something that could cause porosity or other weld flaws.
If the gun was run over by a tractor, there is a good possibilty that it has been damaged more than just the liner. If it worked good before and doesn't now, even with a new liner, the gun power cable could have been damaged and is causing the burn back. The tension on the wire reel needs to be set properly too. Sometimes it will tighten/loosen from the wire turning. It shouldn't freewheel but have just a slight drag. What size wire are you using? I had trouble running .023 wire in mine but .035 worked excellent. If the wire isn't feeding smoothly off the spool will cause burn back. I've seen rolls of wire that were poorly wound and the wire was wrapped under itself causing it not to feed. If a bunch of wire came unspooled on the reel and is loose will also cause problems. Dave

 

[Anonymous-0]

Depends on what flux-core wire is used. Dave

 

[Anonymous-0]

If the wire bumps the work on start up (you'll feel it in the gun handle)it can momentarily stop the wire feed allowing the wire to freeze to the tip and it will burn back to the tip in the blink of an eye. Try pulling the trigger with the tip pointed away from the work and "sweep" it into the work.

 

[Anonymous-0]

First thing that comes to mind is wire speed. I worked for 5 years in a plant that welded frames for Ford Explorers, so I'm basing my answer on that experience. If th wire is feeding out too slowly, you'll experience burnback almost every time. Now from there, you have to determine what's causing the problem with wire speed. Maybe the liner's snagging just a bit...maybe there's some crud/crap/rust on the wire [you did mention it's not copper coated]...maybe your feed rollers are either worn, or have some crap on them...mabe your wire "stick-out" distance past the nozzle is too short...or maybe you simply have the wire speed set too slow. All these factors can contribute to burnback problems. You just have to figure out which one it is.

At the frame plant, tips, nozzles, and diffusers were considered "consumables," and if you started a shift without at least a couple of spare tips in your pocket, you were asking for trouble. Nozzles got replaced when the ends began to "cavitate," and diffusers got replaced about once or twice a week just because of their exposure to stuff taking flight back from the weld site.

But I'm sure there are folks on here who have a lot more experience wth a MIG welder than I.

 

[Anonymous-0]

There could be a problem with the slow wire run in on the machine too. It's a great feature but if it's not speeding up to you preset speed as fast as it should, would cause burnback. Dave

 

[Anonymous-0]

Doug is correct. ANY rust on the wire will cause arcing between the wire and tip. I've found rust on brand new wire! Maybe spooling off the outer layers can help if the welder is in a damp local and isn't used much.