MIG trouble, Hobart wire

[walker]

I was having trouble with my MIG today, MM185. The wire would melt back to the contact tip and stay in a molten ball there and the arc was very erratic. I checked my ground clamp, the usual culprit, and wire brushed the terminals clean. This had no effect, so I cleaned the terminals in the machine, changed the contact tip, cleaned the nozzle, checked the c25 flow, reset the drive roll tension, and it still would burn back and arc funny. Then I decided to change the wire spool to a new one, even though the old one still has a couple of pounds on it. The old wire is the praxair brand prostar er70s-6 and has a plastic spool, the new spool is Hobart er70s-6 and has a spool made of 1/8" rod. I put the new spool on and as is spun it would hit the screws inside the case and arc. I ended up bending the outer edge of the spool in a bit but am not thrilled with this setup. Has anyone else experienced this? what did you do for it?
After I got the wire up and running it welded much better. I am not entirely convinced that it was the fault of the wire for the machine to weld funny like that. Has anyone else experienced that, and what did you do for it?
Thanks for the help.

[Revlimit]

It's never happenned to me. Sorry

[Paul Seaman]

There may be a section of the wire that is actually thinner diameter than the rest and now its giving you feeding trouble. My guess is tightening the feed rollers may help. Also the fact that changing the roll of wire made it better my say that the wire has some corrosion on it and its not getting good contact at the tip and burning back, or the contact tip is worn and not making conection to the wire.

These are a few ideas, mull it over and see if it helps.

[Sberry]

Also check the wire reel tension, too much drag makes them run poor too.

[Paul Seaman]

Sberry good point I have heard of them tightening over time by themselves, from the action of the spinning. Haven't experienced it myself but I've heard of it happening.

[VBI]

I have not experienced a standard wire spool contacting the inside of the machine however there are some differences between the plastic and newer wire cage style spools that my have potential for problems.

The plastic spool has a built in hole on both sides to engage your machines spool spindle projection so you have adjustment over the amount of resistance to spool rotational free wheel.

The last wire style spool I changed had a clip-on metal tag (so to speak) that needs to be placed on the correct side of the spool to match your machine. If the clip-on is missing or on the wrong side of the spool it may contribute to alignment problems.

Another possibility for your other concern, wire burn back with erratic arc, is when there is a wire feeding restriction caused by a kink in the liner, or too many tight bends in the liner while welding. Sometimes the most frustrating problems can be the simple ones.