MM 210 Liner Replacement Question

[davvet2]

I replaced the liner in my 210 last year trying to solve burn back problems. Instructions said to cut 3/4" off the liner at the gun head, which I did.

Now, I realize that there is liner sticking out of the brass on the roller end and the assembly isn't seated all the way down. (see photo)

It's about 1/2" away from the rollers, but the steel liner protrudes and it's 1/16" away from the rollers.

Do I need to cut the steel liner back to the gun assembly brass fitting and readjust? If I do this, will it make my liner too short?


After I called Century and they told me the gun assembly on my 140 needed to almost touch the rollers because it affected amperage, I wondered if the same thing might be true on the 210.

Also, should the contact tip stick out past the shield cup or is it recessed?

Finally, does Miller have tech support by phone?

Thanks!

Jim

[Archaic]

Jim:

Someone more knowledgeable will hopefully come along, but I will take a swing at your question. Understand that my experience is with a MM251 and a Miller M25 gun.

No, DO NOT cut the steel liner back to the gun assembly brass fitting. I have gone to Bernard guns on my 251. If you looked at one of them you would see that on the machine end, rather than a section of steel liner sticking out, there is a brass nipple that when the gun is seated into the machine and clamped down the end of the brass nipple is approximately 1/16" (or less) from the roller. From the center of the roller the wire is in tension to the spool side. From that point to the gun side it is being pushed. Cutting off the liner as you questioned in that area would just give space for the wire to buckle and birdnest. The liner should not touch the roller, but be as close as possible.

Liners, as they come from Miller, and after you cut it, tend to have a very sharp, rough edge towards the wire. I file this down to produce a very smooth edge. No chance for the wire to snag entering or exiting the liner.

I am not sure how the Century liner position effects amperage. This should not be true on the Miller. The liner does not carry current. Current to the wire occurs at the tip.

The Miller O&M can be somewhat confusing. The liner should be cut 3/4" OUTSIDE the head tube. Not 3/4" back INSIDE the head tube. The gun end of your liner should fit up into the brass adapter providing a smooth transition from liner into adapter into tip. I will attempt to attach a picture from the M25 O&M to this message showing this. You can download the M25 O&M from the Miller site.

Whether the tip sticks out, is flush, or is recessed is a function of which nozzle you have. For most welding, I would suggest that you use the 200258, 1/2" orifice, flush, or what I typically used was the 169726 5/8" orifice, flush. This is not completely true, but recessed tip nozzles tend to be used for spray arc welding, tip stick out nozzles for hard to get to areas in welding. Generally speaking, you will get better gas flow and welding when using a flush nozzle. But, you may find that for your style of welding a recessed or stick out nozzle works better.

Hope that I helped and did not give bad information.

Adios-----

Well, I can't upload the file as it exceeds the fourm's 100 KB restriction. Rats! What you should have is 3/4" of liner sticking out past the end of the head tube when cut. Make sense?

[cruizer]

Lay the gun out straight( no bends, no coils) remove the old liner and replace it with the new one. tighten allens screws, or caps.

Cut 3/4" from the torch end. this is for liner and wire strain relief by the way.

Insert into machine. Now some guns have this liner stick out, some don't, and some machines have a separate liner altogether.

If the gun liner strikes the drive spools, before being inserted all the way, then trim it back simply to prevent the drive wheel from wearing prematurely and proper drive engagement..

[hankj]

Jim,

The spacing from the end of the liner to the drive roll shown in your picture is correct. It has nothing to do with amperage. It prevents the electrode wire from kinking at the liner entry point.

Hank

[davvet2]

Thanks, Guys --

I went about readjusting the spool and roller tension today, and for awhile the machine welded great on 18 gauge metal. After about 30 minutes of testing, it started burning back again. The speed was on 18, the heat on 2 -- I raised the speed to about 22, and it didn't make much difference.

There must be something wrong internally for the welder to do this. I've had it since May '05, and haven't been able to get it to work right yet. I've replaced the liner as was suggested, tried different wire, contact tips, reset the tension on the rolllers and wire spool -- but it always come back to the same problem, burning back and welding the wire to the contact tip.

It's under warranty, do I have to contact Miller before taking it in for service ?

My problem was having the vehicle to get it there -- I now have an F-150 and a set of ramps to get it loaded.

Thanks,

Jim

[cruizer]

Nothing wrong with the welder, simply use "1" knurled drive roll gaged to the size of wire perferably on the bottom You only have to tighten the drive a little to achieve the required results.

[Roospike]

I didnt reread the thread but also bad wound wire can cause burn back. I have had 2 bad rolls within months do this to me.

cruizer also has good input about the one knurled drive roll on your power drive wheel.

[davvet2]

Nothing wrong with the welder, simply use "1" knurled drive roll gaged to the size of wire perferably on the bottom You only have to tighten the drive a little to achieve the required results.

Forgive my ignorance, I am a nube. My drive rollers are .030 on the back side .035 on the front. They are lined up, and the wire is in the .030 groove.

The sticker on my machine shows a knurled roller for flux wire, but the smallest is .035.

Is that what you're suggesting?

Thanks,

Jim

[hankj]

Jim,

Wire feed should be smooth and burn back shouold not be an issue. My 210 has run flawlessly on any wire I've used.

If you did just change out a spool when this started, Roospike's tip is a good one to check out.

Hank

[Danny]

Are you running and .030 solid wire and 75/25 shielding gas?

[davvet2]

I've tried several rolls of wire; no difference. I'm running .030 with 75/25.

Thanks,

Jim

[Danny]

Your wire speed is way too low for voltage tap #2

[cruizer]

If the wire cannot be spooled in the palm of your hand, you have a drive problem, now if your running 030 wire, why are you using 035 drive wheels. All your going to get is alot of slipping, thus burn back into your tip. Maybe switch to 035 wire and go my route with a single knurled drive wheel, and yes Miller does have them for your machine.

[mowjunk]

Your wire speed is way too low for voltage tap #2

Dan's right - (as usual)

I think 2/28 is about right according to the chart on the 210 for 75/25 gas....... 2/18 is for 100% CO2...

mow

[davvet2]

If the wire cannot be spooled in the palm of your hand, you have a drive problem, now if your running 030 wire, why are you using 035 drive wheels. All your going to get is alot of slipping, thus burn back into your tip. Maybe switch to 035 wire and go my route with a single knurled drive wheel, and yes Miller does have them for your machine.

I'm running .030 drive wheels and .030 wire. The wheels are combination wheels, one side is .030 the other .035. I have them both set up for .030.

What is this "spooled in the palm of your hand"?

I was told by a board member last year to adjust the tension so that I could pull the wire through the gun by hand, and that's what was done. I don't have a problem buying the knurled roller and .035 wire.

I just wanted the machine to operate correctly (which it's never done). I spent two grand on this setup including the spoolgun and jugs -- and it's been sitting since 2005 because I wasn't smart enough to get it working.

Thanks

Jim