Aluminum Welding Issues

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First i want to say, that I used to do a ton of aluminum welding 10 years ago or so...and always remembered hating it.  Well now i have a Lincoln 255 with a I believe Magnum spool gun (the $2000 one).  What i am hating or can't seem to get past is, one second it is running nicely...perfect heat, nice looking weld etc, and then it all goes to hell.  Quite often the wire just quits feeding.  That seems to be the main problem.  It will either seem really hot or the opposite, it will be hard to get it to flow and will just ball up on the piece i am welding.  Then just as quickly it seems to cure itself.  Looking at the wire it seems like from time to time it is pinching the wire too hard.  What i am wondering is, i am seriously considering a MP 350 as i have alot of aluminum coming up and am just plain tired of dealing with this spool gun.  Question is, is there something i am missing with these spool guns a way of getting them to run smoother?  Or should i just cut my losses and shell out the $5500 for an MP?
Reply:I have Miller spool guns and have never had a problem like you describe.  Are you sure you're not losing the ground (work) connection?  As the aluminum you have been welding builds up heat, it should be easier to weld....in fact you should have to start moving the spool gun faster to avoid burn through.  From your description, it sounds like you are losing either the work connection, or you have a loose electrical connection going to the gun itself.  Spool guns make MIG welding aluminum easy, so you should not be having these aggravating problems.  Best bet would be to call Lincoln and see what they think.  This is NOT a normal condition.DougMiller Syncrowave 350Millermatic 252/ 30A spoolgunMiller Bobcat 225g w/ 3545 spoolgunLincoln PowerArc4000Lincoln 175 Mig  Lincoln 135 Mig Everlast 250EX TigCentury ac/dc 230 amp stickVictor O/AHypertherm 1000 plasma
Reply:Rereading your post, I'm not sure if I understood it correctly.  Are you saying the wire stops feeding from the gun at all, or that it feeds but balls on the workpiece?  Your feed rollers in the gun should be set to just feed the aluminum wire reliably and not any harder than it has to be to do that.  There is a procedure you can follow to test the feed roller setting by letting the wire hit the workpiece with no ground attached and see if it curls the wire up as it feeds against the work piece, but I never do that.  I just barely have the rollers grab the wire to make it come out smoothly.  Start with the rollers not feeding the wire at all and gradually increase the roller tension until it feeds reliably.  You might have clogged the little feed grooves with sheared aluminum by incorrect setting.  If so, clean your rollers.  I hope I haven't misunderstood your question.  If so, please ask it again.DougMiller Syncrowave 350Millermatic 252/ 30A spoolgunMiller Bobcat 225g w/ 3545 spoolgunLincoln PowerArc4000Lincoln 175 Mig  Lincoln 135 Mig Everlast 250EX TigCentury ac/dc 230 amp stickVictor O/AHypertherm 1000 plasma
Reply:The wire quits feeding, the drive roll keeps rolling and the gas keeps working but the wire just stops.  I don't have enough wire through to worry about the liner even though i blew everything out to be sure.  It dosen't wreck the tip, once i pull the wire out a bit to get it running smoothly again i can see the dints in the wire from the roller.  But then some times i will hit the trigger and it seems that i turned the welder up 2 or 3 volts.  This only happens with the spool gun, with the wirefeeder (steel) it works perfectly.
Reply:it's possible your gas flow is a little low.Sounds like the wire and tip are getting hot and changing size. this causes the wire to stick in the tip.correct size tip and gas flow are key to good welding. correct drive rolls helps also.A little higher gas flow will help cool the tip and keep the wire feeding.worn drive roll will cause feeding problems. Worn tips can cause damage to the drive roll.gas flow should be 25 to 30 cfh. drive roll pressure set to high will deform the wire and cause problems. If one type of wire (5356) does not weld nice switch to (4043) and try it.5356 is hard and welds with soot. 4043 is softer and cleaner. 5356 is stronger, 4043 welds pretty. there is a chart in the operators manual that matches the different types of aluminum.Lincoln might be able to help. but if it is a magnum spool gun k486-25 it is made by systematic for lincoln. python and prince guns are made by MK products. the magnum 100 sg is their new one.