Sick MIG

[Mills]

I have been building a railing for my parents place and it was coming along quite well til my mig hiccuped, a LOT. It is a '78 Miller with leads you switch between jacks like some old Forney stick welders I've seen.

Can't seem to get the wire to feed. This was given to me with a spool of wire in it. It sat for quite a while before I got it and the wire was very dusty on the outside of it. It was almost full, though. I have used up the spool tonight. It has put down the entire roll till now without a hitch. I had replaced the liner when I got it and the tip seemed to be fairly new so I left it on. I have had this thing cranked up laying down a lot of bead for a couple of hours at a time the last 3 days. When I started having trouble I started diggin in deeper and deeper. Found a lot of gunk in the tip and in the part the tip screws into. A lot of build up in the end of the liner, as well. Decided to switch out the liner with the old one that I kept just in case but I bent it while hurrying as fast as I could. I now have the newest liner soaking in kerosene. Was told that was a good way to clean them.

Any advice from those in the know?

[aametalmaster]

I used to use paint thinner to keep mine in then blow it out with an airhose before putting it back into the gun...Bob

[Dodge]

Are you sure the liner is the problem? Do the feed motor and/or rollers turn?

[Ten Hammers]

Like Scott says, check the feed rollers. Remove the gun and check to make sure that the connection between the gun and welder is not obstructed or damaged in any way. Liner should come up to the front roller but not touch. Other end should allow the tip to screw in freely to the bottom ( unless you have a Bernard gun or some other type that tip slides and twists ). Unobstructed gun and tip now. Gas nozzle should be free of boogers and nothing to touch contact tip ( grounding the nozzle ). Back to feed rollers. Check the electrical connection between the gun and welder. This allows the trigger to run feed rollers. Each time the gun is triggered, the roller motor should click and advance according to your wire speed adjustment. I'm unfamiliar with your particular model. I have a Miller 172 here at home. I run CP 250's and CP 300's at work. Check your feed rollers to be sure they are turning. Check to see if they are dirty and/or damaged. Runnin gunky wire through them may have worn then a bit but sounds like you got along ok with liner replacement. Check to see if the rollers TURN when you trigger. I have a glass 5 amp fuse in my circuit. Too much pressure on the top bearing of the rollers will blow this fuse ( located on opposite side, accessed by removing cover of welder ). Good idea to remove this cover anyway and blow out nasties. Be careful. Use one of those clip pocket blowers and don't blast the circuit boards with hard air blast. Check contacts to be sure they aren't contaminated. I would also be contacting a dealer for any paperwork showing schematics. You may be able to access these on
Millerwelds.com - Home don't know. Also check wire spool tension. Should be free but not enough backlash to cause problems. Yes, I clean liners with brake parts cleaner and compressed air. I have no tank to soak them in but I guess a bucket would work. I also might shove some wire through the liner with a little bitty bend on the end to break up any crud and then continue to spray and clean. I use pre-roller clip on felt wipers and have also used paper towels clipped on same place with an alligator clip for same purpose. Good luck. I sure ain't no expert or service tech. Just have a little experience.

[Mills]

I am always amazed at how fast and on point smiths are.

I have a Tweco 16' lead. Liner placement, I will be reinstalling today and see what happens.

Feed rollers: Yes, they are turning. I have cleaned them w scotch brite pad and scraped some gunk out of the groove with small screwdriver. I have retensioned the spring that holds them together. It feeds just fine till the last couple of feet then things start going south.

End of the gun: Didn't realize the nozzle would ground the tip. I guess that explains the insulation it sits on. I definitely need to replace nozzle and insulator. And that MAY be the cause of at least part of the problem.

Electrical: I have been through the whole gun when I got it, tracking down a short. Replace spade terminals and cleaned contacts, etc. I have used a Scotch Brite pad as a preroller wiper I may use a clothes pin to give it a little more bite. Good to see that it is a sound idea.

I have run .045 wire through the liner to push out crud but it stops at various places like it is bulldozing more and more crud. That doesn't make sense to me. Is it possible that one roll of wire could build up that much in the liner? Yes it was a dirty roll from sitting, but after the top layer it was bright and shiny. It had been in the machine with the cover down so I discounted the top layer.

One other thing I noticed is as I ran wire through back and forth checking roller action, etc. is that I could feel a roughness near the gun end. But back feeding the .045 wire though resulted in nothing that I could feel.

I am about convinced in reviewing this that I have a liner problem and I should run some brake cleaner through it next. No compressed air, darn it.

Another question, when do you replace the tip? I have seen this become egg shaped. I have ground it back some in trouble shooting to see if that had an effect.

[mountainman]

Make sure the rollers are adjusted so as the wire feeds thru okay,.
As far as the roughness in the gun, it comes from a bad liner and also a bad tip.
Mountainman

[irnsrgn]

the copper tip is where the wire picks up the electricity, if it is egg shaped at all, welding will be intermittant, grinding back will not help, I usually go thru about 3 or 4 tips per roll.

[Ten Hammers]

Just to answer your question, yes, less than one roll can contaminate your liner. I got some Forney wire from the local farm store ( because like a moron I ran out of Harris from the supplier ). The forney wire clogged the gun/liner in about as quick as you can weld. It may have been in the store for a while, don't know. I do know this. Current wire mfg is in China and also Mexico. I have not searched really hard but this is what I have found ). Work wire recently was Mexican. Before that was Chinese. Get it hot nuff, it'll run. I don't replace tips till they start stickin wire. Everyone's different. We have a moron at work ( and yes he's a supervisor that doesn't weld ) that is like pullin teeth to get a nozzle or tip from him. One operation, I can fry a nozzle in a day ( mebbe 2000 welds 1 1/2" long and runnin hot ). Pays to have connections with the boys and the stash of consumables. I also use vaseline for nozzle dip but it will spoil a nice piece that you plan to oil finish. If you are going to blast or acid treat, then it's fine.

[irnsrgn]

Just so you will know, I use only one brand of wire in my Mig Welder, its copper coated, Hobart HB28, its an E70 S6 wire and it works the best with my type of work where I mainly use hot rolled as is and for repairs of small things that are dirty or rusty.

[Ten Hammers]

ER70S6 wire is all I use as well Junior. you might check the wire mfg country of origin. If it is USA, please let me know cause I want some. I get my wire from ( former ) Universal Welding ( now Linweld ) in Ottumwa. 10# is all that'll fit my little rig at home.