First MIG welds-troubleshooting

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This is my hobby welding setup:120V Mig/fluxcore unit (4position selectable output,infinite wire speed adjustment) running on a 20A circuit..030" Hobart ER70S-6 wire40cf of C25 with flow set at 15-20cfh per the regulatorThis is my first test with it configured for MIG.The workpiece was a flat piece of slightly rusty 1/8" steel to test this small machine to its maximum (Output on this small box is only 70A). Since I learned to weld with my 230V buzzbox,this little box is only for light sheet metal jobs (exhaust pipes and body work mostly). I prefer my buzzbox for anything thicker than about 12gauge. I've used this machine with flux core on 1/8" steel and it works quite well. I picked up a bottle so I could test it with gas. The object is eventually to be able to use it on thinner steel that I can't otherwise weld with flux core. First MIG problems:1. It seems like the arc is stuttering on and off at a very rapid rate. What could cause that? I don't have that problem using flux core. I don't think it's the wire feed rate,as I'm keeping a constant length that is not sticking out too far when I end the weld,and it's not burning back into the tip. I'm not feeling the "bumping" effect from too high of a speed either,so I'm pretty sure that it's not set too fast.2. The bead itself is pretty high,not smooth and is piling up randomly in bubbly teardrop shapes,so I'm guessing that my voltage is too low,and possibly my travel speed is too high? It settles down a bit smoother if I stay in one place,but then it looks like I'm dumping too much heat into the workpiece.Technique-I'm dragging the gun, and am keeping the travel angle around 30deg or so from vertical.3. Gas flow seems consistent and the weld bead itself is very clean,but I am getting a bit of brown and black soot residue along the side of the weld from time to time. I can't figure out where that comes from,or if it's normal.Any ideas,or am I just pushing the machine too far with too thick of a workpiece?
Reply:Originally Posted by Squirrel slightly rusty
Reply:Clean your material, turn your gas down to about 7 to 10 and once again, clean your material.John -  fabricator extraordinaire, car nut!-  bleeding Miller blue! http://www.weldfabzone.com
Reply:The norm for light duty welding is short-circuit-transfer. What that describes is the way bare wire becomes weld metal and it produces a distinct sound, sort of like a small ratchet spinning very fast. The gas we use for mild steel is 75%-25% Argon-Co2. I don't have experience with straight Co2.Rusty Wrangler is right, the cleaner the metal the better your chance at making a good bead. Clean the weld zone after every bead. Wire stick out needs to be consistent, 5/16" should be close, I usually push the bead slightly and keep the gun centered left-to-right directly into the joint. The motion I use is zig zagged watching the left edge then the right edge. It must vary according to the particular joint type you intend to make, but with me, they are all similar except for open root butt joints. No zig zag there, it is more of a U-shaped motion to avoid leaving cold wire in the joint.City of L.A. Structural; Manual & Semi-Automatic;"Surely there is a mine for silver, and a place where gold is refined. Iron is taken from the earth, and copper is smelted from ore."Job 28:1,2Lincoln, Miller, Victor & ISV BibleDanny
Reply:Thanks folks.I wasn't hearing the usual even flux core sizzling sound,so I figured something must be wrong. I usually go by sound to tell how the wire is burning.Having learned on stick,I'm a bit lazy about cleaning my workpieces. I'll hit it with the grinder,and turn the gas down a bit. Also will try a different weave. Just to clarify, I'm already using 75%argon and 25% CO2.
Reply:I think the problem here is that the material is quite thick for your machine for MIG. I encountered the same problem.  What you need to do is increase the wire speed alot.  I found that the wire speed for MIG is much greater than for Flux core.  Try putting the speed at like 6 or 7.  I think you'll get better results.
Reply:You did switch the polarity when you changed over from fluxcore to mig, right???
Reply:Originally Posted by fordtrucksI think the problem here is that the material is quite thick for your machine for MIG. I encountered the same problem.  What you need to do is increase the wire speed alot.  I found that the wire speed for MIG is much greater than for Flux core.  Try putting the speed at like 6 or 7.  I think you'll get better results.
Reply:Originally Posted by SquirrelYup, but I'll check it again to make sure. I'm almost tempted to test it at the other setting,just to see what happens. It's definitely harder to strike an arc on the MIG setting vs the flux core setting.
Reply:[QUOTE=Squirrel]I'm actually under setting 1 right now,which is about where I run it for flux core on steel. If I run it too high, I get a lot of "bumping" and pushthroughs on thin steel.I do agree that probably the material must be a good part of the problem. Luckily this is the absolute thickest material I would even try with a wirefeed, and both stick and flux core works well on 1/8".I think that for a 120v machine its highly unlikly that you will push through a 1/8 in plate, not with MIG, maybe with flux core.  But flux core really burns alot hotter that mig.  Setting 1 seems way too low for MIG on that plate with a 120v machine.  Just to calrify do you have the maximum plate capacity for your machine?  It's probably 1/4 or 5/16 with flux core.  Mig would be alot lower. like maybe 16 guage?
Reply:Try setting the voltage on HIGH, then weld with one hand.  Turn the wire speed with the other till you get a nice sizzle sound.  The arc should start instantly with absolutly no problems.  From the description of your bead, its way too cold.DavidReal world weldin.  When I grow up I want to be a tig weldor.
Reply:Originally Posted by fordtrucksI think that for a 120v machine its highly unlikly that you will push through a 1/8 in plate, not with MIG, maybe with flux core.  But flux core really burns alot hotter that mig.
Reply:Sounds similar to the problem I had switching from flux core to MIG.What stickout are you routinely using?  I found MIG stickout should be much less than with flux core.Favorite right now is a Miller Syncro 200.Tons of tools and I blame at least one of them when things don't go right.
Reply:What brand machine do you have?
Reply:Me?  My MIG is the HF dual MIG 151.  Run many spools of wire through it and it gets the job done once you get pretty good at it.  It ain't no Miller though.Favorite right now is a Miller Syncro 200.Tons of tools and I blame at least one of them when things don't go right.