Attempting to learn to MIG aluminum

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Hi - I am a novice welder.  I have learned to weld steel over the years with a lot of reading and a lot of practice at Busted-Knuckle U.  I have had a lot of success with steel and now I am attempting to learn to weld aluminum.  I purchased the aluminum kit for my Lincoln 135 and installed it.  Good news is that so far I am not having any feeding issues.  I have had a couple good beads, but my biggest problem is burn-back.  Seems that when the arc starts it immediately goes straight back to the contact tip and I immediately lose the "crackling bacon" sound I am so used to.  Often the wire forms a glob on the contact tip.  When I do get a nice "crackle" going, I get some decent beads or burn through the 1/8" I'm practicing on.I am using the .035 wire/contact tip from the lincoln aluminum kit, 15cfm (what I use for steel) straight argon, and I have varied the output, and wirespeed.  I have found that the few nice beads I have had are when I move the torch in a fast small circular motion like you would with a gas torch - but sometimes I get burn-back immediately at the start.  I have increased the wirefeed as fast as it will go.Anyone have any suggestions for me to try?
Reply:Check the polarity DCEP, the ESO, voltage. wire reel must be lose.  feed rolls not to tight, inlet and outlet from the freed rolls,in line, clean liner, streight torch and an .o40 or .045 contact tip.  There should be no crackling, like in steel welding, only Spray.  This should help and welcome to the group.  JohnSMAW,GMAW,FCAW,GTAW,SAW,PAC/PAW/OFCand Shielding Gases.  There all here. :
Reply:Based on my own findings, the ESO, electrode stick out, for aluminum is about double that of steel.    On my Lincoln Pro-Mig 175, I keep about 5/8".    Be in motion as you pull the trigger.    Depending on the thickness of material, you have to be cautious not to linger in a spot for too long.    The thinner the stock, the more motion (spread out the heat) and conversly, the shorter the beads (limit the heat) should be.    It will be difficult to MIG thinner than .100" aluminum without it being all just tack welds.Increase your wirespeed and travel speed and voltage settings as compared to steel.      When mig welding aluminum, things happen much faster, especially the bad stuff.15 on gas is a bit low, I'd recommend higher, say 25 or so.     Don't watch the arc.    Push the weld and watch the puddle behind the arc.Learn to react by how the puddle behind the arc behaves.I prefaced this with "Based on my own findings" because I'm not a professional welder, just a self taught hobbiest.      I'm sure there will be an expert or two to chime in later and tell you you can't do aluminum with a small mig (I'm actually surprized it hasn't happened yet), but rest assured, it's possible.There are no small projects
Reply:You are doing ok, don't feel bad. I second trying a .040 tip for alum. .035 wire. The aluminum actually swells a bit with current in it, and it also tends to drag in the tip. Keep the line as straight as you can, twists and turns will make the wire drag a LOT in the sleeve. And if you have the preset regulator, you won't be able to get more gas flow. But you will be all right. If you can get more gas flow, I would say go up a bit, it will help. And finally, I agree with imagineer, I tend to keep a longer stickout than I ever would with steel. I used the same basic machine for quite a while, you can get some decent welds with it, with practice!!!And then, after so much work...... you have it in your hand, and you look over to your side...... and the runner has run off. Leaving you holding the prize, wondering when the runner will return.
Reply:Cool - so far I'm very encouraged with my results even though I'm having some burn-back problems.  I fully expected this to be a much harder learning curve than with steel.  I actually didn't think that I would see any decent beads for a while, but I've already had a couple nice ones.  I'll take it!I'll check over my feed tension and rollers, and my ESO is definitely not 5/8", so I will try that.  Also I'll bump up the gas flow to 25cfm.  Now I just have to find some tim to try again.  This weekend I have to swap out parts so I can do a steel weld job on a table saw for a buddy of mine.Thanks for the input.
Reply:I would suggest you read the sticky post on this board about mig welding modes. Globlar transfer is very difficult and short circuit welding of aluminum is next to impossible. The spray transfer mode may be easier for you as a beginner.  And ditto on "things happen fast".SA200,Ranger8,Trailblazer251NT,MM250,Dayton225AC,T  D-XL75,SpoolMate3545SGA100C,HF-15-1  RFCS-14 When I stick it, it stays stuck!
Reply:The Electrode has to be on the positive terminal and make sure to clip the wire allways before starting the arc.  If there is a ball on the end of the wire, it will build up current in back of the ball and snap off at the contact tip.  Just some tips.   JohnSMAW,GMAW,FCAW,GTAW,SAW,PAC/PAW/OFCand Shielding Gases.  There all here. :
Reply:Originally Posted by imagineerBased on my own findings, the ESO, electrode stick out, for aluminum is about double that of steel.    On my Lincoln Pro-Mig 175, I keep about 5/8".    Be in motion as you pull the trigger.    Depending on the thickness of material, you have to be cautious not to linger in a spot for too long.    The thinner the stock, the more motion (spread out the heat) and conversly, the shorter the beads (limit the heat) should be.    It will be difficult to MIG thinner than .100" aluminum without it being all just tack welds.Increase your wirespeed and travel speed and voltage settings as compared to steel.      When mig welding aluminum, things happen much faster, especially the bad stuff.15 on gas is a bit low, I'd recommend higher, say 25 or so.     Don't watch the arc.    Push the weld and watch the puddle behind the arc.Learn to react by how the puddle behind the arc behaves.I prefaced this with "Based on my own findings" because I'm not a professional welder, just a self taught hobbiest.      I'm sure there will be an expert or two to chime in later and tell you you can't do aluminum with a small mig (I'm actually surprized it hasn't happened yet), but rest assured, it's possible.
Reply:vtwin, how goes the welding.  Trying to decide if I should keep the little lincoln 100 my wife  bought me because I would like to do aluminum for things like a subframe, luggage rack for (soon to purchase) super motard...so mostly small stuff.  sounds like we're at the same place, used my father in laws tig to build a very sturdy trailer but sounds like mig welding aluminum is going to be difficult (tig on the trailer was easy).so, any updates? ...and what  bike.  bought a liter vtwin 10+ years ago myself and can never see going back to a 4 for the street.