Problem with MIG arc

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I have a problem with MIG, and I can't figure it out. I'm hopping someone can shed some light on this predicament. I've been doing SMAW and FCAW for a number of years; so I decided to get into MIG.  I bought a TWICO 211i and I've been doing fairly well, but there are times when the arc will go silent with no sizzle and a big glob of metal forms on the tip of the wire. I've tried a number of different settings, and I found that if I crank up the wire feed way out of proportion with the voltage, I will get the sizzle back, temporarily, but after a while it will revert back to globing the molten metal back onto the wire – even with the higher wire-feed setting.  I have been watching the stick-out, but that doesn't seem to make any difference, and I have tried placing the ground closer to where I am working, and that made no difference either. My ground is negative and the wire is positive.   The sound reminds me of a young boy whose voice is changing – it will sizzle along and then start cutting out.    .
Reply:This sounds to me like a burnback problem. First thing I would check is the tension on the drive rolls. I think it should be just tight enough that it will feed through the contact tip with a bit of resistance and without slipping on the drive rolls. Also, I would pull the wire out from the gun and blow a bit of compressed air through the gun liner to clear it out; sometimes dust and gunk get built up in there and cause problems. Also make sure the contact tip has a clear orifice for the wire to travel through.
Reply:There's a whole laundry list of things to check. Correct drive roller size, correct contact tip size, clean contact tip, adequate ground, etc. Not to mention settings in general. Start with the door panel recommendations. And be sure to clean your metal to be welded, both where you will weld and where you will ground. Don't ground to the table. Ground right to the part to be welded.Miller Multimatic 255
Reply:A bad  connection will give you fits too,like if you have a corroded connector getting hot or mostly broken wires.
Reply:Hitting spray transfer mode will also cause the welder to go silent, or nearly so....It is possible to hit spray transfer at just over 20 volts and it will be intermittent like you describe, but the wire will not glob up with molten metal like you describe.I agree to start with your whole wire drive system first. Rotate wire back onto the spool and tie it off to spool and first adjust spool tension to stop spool from rolling after you stop welding...Not too tight, but just tight nuff to stop it from causing birds nest at spool.THEN examine your drive rolls and make certain you have proper groove selected for the wire, AND the rollers are exactly in line with the wire inlet and outlet. From there determine wire drive compression is correct on the tensioner by doing the wire into wood thang.Feel free to open the door and squirt lots of wire out as you watch the spool roll and look for RPM changes. Just turn off gas bottle and leave ground clamp off and squirt out the wire...Then release the tensioner and roll the wire back on the spool so as to not waste it.
Reply:I suspect slipping drive rolls as well.
Reply:Thanks, forks for your good advice.  What I did was pull out the wire from the gun and sent a blast of air through the wire cable (didn't notice anything coming from the other end), changed the tip (even though the old one looked OK), and I adjusted the pressure on the rollers to what I thought, correct.  I did this by pinching, with my fingers, the wire at the gun while pulling the trigger. I stopped tightening the rollers when I saw the wire continuing through my fingers.  Feeling positive, I adjusted wire speed and voltage to chart specs and lit up an arc ..... It still globed my wire! I stood there stunned looking at that TWICO ... what is wrong? ..... It had to be the wire feed; so I really screwed down on the roller pressure, and started another arc.  this time, I got a nice sizzle from the arc and a decent looking bead.  The problem was the roller pressure.  The TWICO's graduation is 1 to 5, and I ended up between 2 and 3.  When the 8" wire roll was new, I didn't need all that much pressure on the rollers, but the roll, now, is about 3/4 empty; so I will have to monitor the size of the wire roll and make appropriate adjustments to the roller pressure in the future. Thanks, again for pointing me in the right direction.
Reply:Originally Posted by DennisK  When the 8" wire roll was new, I didn't need all that much pressure on the rollers, but the roll, now, is about 3/4 empty; so I will have to monitor the size of the wire roll and make appropriate adjustments to the roller pressure in the future. Thanks, again for pointing me in the right direction.
Reply:Those 8" rolls do get tighter as you get towards the end of the roll.Ed Conleyhttp://www.screamingbroccoli.com/MM252MM211 (Sold)Passport Plus & Spool gunLincoln SP135 Plus- (Gone to a good home)Klutch 120v Plasma cutterSO 2020 benderBeer in the fridge
Reply:No, they do not get tighter.You lose mechanical advantage when spool of wire gets smaller...Exactly like on rear sprocket of multi speed bicycle.Tension on the anti free spin adjustment does not change as spool gets smaller, but you have to pull the wire harder to spin the spool because of less mechanical advantage...The lever arm becomes shorter, but the torque required remains the same.So set spool anti free spin tension lighter-just enuff to prevent free spoolin when you stop welding.
Reply:Originally Posted by wornoutoldwelderNo, they do not get tighter.You lose mechanical advantage when spool of wire gets smaller...Exactly like on rear sprocket of multi speed bicycle.Tension on the anti free spin adjustment does not change as spool gets smaller, but you have to pull the wire harder to spin the spool because of less mechanical advantage...The lever arm becomes shorter, but the torque required remains the same.So set spool anti free spin tension lighter-just enuff to prevent free spoolin when you stop welding.
Reply:To close this problem:  Today (before the rains come), I did as I said I would.  I backed way back on the spool hub tension to a little before bird nesting, and I lessened the roller pressure to the point that wire would feed through lightly pinched fingers (setting #1).  My welds are back to where I want them.  I know, now, that there is a critical coordination between the wire hub tension and the wire feed tension, and that this varies with the volume (circumference) of wire on the hub. Factory set tensions should be questioned.
Reply:You are welcome, glad I could help.Trust me, you won't have to fiddle with it thru whole roll of wire once you set it in it's sweet spot....Some machines require you remove and reset the spool tension nut every time you swap spools. Some don't.Keep in mind best time set it for the one time adjustment is with full spool before you unravel it and feed wire into drive....Just spin the spool and adjust the nut till spool turns really easy but stops within a small few degrees of rotation-just maybe one or two degrees.A full spool has more rotational stored energy, so it will want to continue to rotate longer.
Reply:You did indeed help, wornoutoldwelder.  Thanks again.   Hopefully, someone else, new to MIG, and with a new machine will come across this to his or her benefit.
Reply:Several of my friends that have purchased their first mig had same issues. LOL, all of us only look at the pics in the instruction manuals at first...I admit I did the exact same thing myself
Reply:I'll be 72 this year - you'd think I would know better.
Reply:Originally Posted by DennisKI'll be 72 this year - you'd think I would know better.
Reply:Originally Posted by wornoutoldwelderNo, they do not get tighter.You lose mechanical advantage when spool of wire gets smaller...Exactly like on rear sprocket of multi speed bicycle.Tension on the anti free spin adjustment does not change as spool gets smaller, but you have to pull the wire harder to spin the spool because of less mechanical advantage...The lever arm becomes shorter, but the torque required remains the same.So set spool anti free spin tension lighter-just enuff to prevent free spoolin when you stop welding.
Reply:I remember 62!  If you like beer at 62, you'll like beer at 72 - judging from personal experience.
Reply:Originally Posted by Broccoli1semantics- ok it doesn't get tighter-
Reply:Originally Posted by DennisKI remember 62!  If you like beer at 62, you'll like beer at 72 - judging from personal experience.
Reply:I have seen the tension nut on some spool hubs tighten or loosen when the reel was turning so may want to put a mark or something on it to see if it may have moved. If it does, put some blue Loctite on it so it keeps it's position.