4043 vs 5356 alum filler & fine tuning Q's

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Hello all,I have a Millermatic 211 with the 100 series spoolgun. I have gone through my first spool of 4043 practicing on 6061 base and am finally starting to get good. I bought a roll of 5356, mainly because it was all I could get my hands on. I was also curious why so many places had 5356, but no 4043. It didn't take long to decide I liked 4043 better.After toying with the settings, I got the 5356 to weld fairly well, but I had lots of spatter, there was a grey film on my gun, helmet, bench, etc- everything nearby. The garage was filled with smoke in a matter of minutes. It reminded me of stick welding galvanized stuff. Whats up with all that? With 4043- no smoke, no spatter, no film... settings? I switched back to what was left of my 4043, and life was good again...100% argon @ 45... Could the new roll be oxidized? Should I unroll a few layers and give it another chance or shove it to the back of the shelf? More questions (fine tuning): Once things are close to set, how do you go about fine tuning? I've noticed If I play with just the roll speed, I can slow it down where the wire almost burns back to the tip and if I crank it up the wire gets much closer to the base before the 'spray transfer' starts. The tip is 3/4" away. Is there a 'sweet spot' or is it personal preference?Finally, I need to weld a piece of 1/4" x 3" flat to a 1" square shaft- both laying flat, so a long fillet weld on both sides of the 1" shaft. I have preheated the bases (6061) with a propane torch to eliminate cold starts. I can get a very nice weld but it ends up being a pretty big fillet weld. any tips or tricks to get a smaller fillet? It seems if I try for a smaller weld, it tends to weld one side or the other.Long post, lots of questions, I know. I look forward to your advice.good luck -jim
Reply:Update,Still don't like  5356- Got 2 new rolls of 4043 and am good to go. As far as the 'sweet spot', I am using the recommended MM211 settings and they seem to be working well. Lots of opinions out there on preheating- I am having good luck with it and will be going that route.On the large fillet welds- 'Hot and Fast' actually seems to produce smaller welds. At lower voltage settings, the filler tends to prefer one side or the other and I really have to go slow and end up with a large puddle to get a good fillet weld. The 'hot-n-fast' puddles quicker into the joint so I can move quicker. good luck -jim
Reply:I'm not sure of the exact reason but Miller does not recommend 5356 filler with the MM211They don't even list it in the chartEd 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:As you can see, the two wires have different characteristics. Both work well with the common 6061 alloy, but 4043 should not be used with 50xx alum. alloys.The grey smoke is common in aluminum MIG, but large amounts indicate poor shielding. 45 CFM is high unless you are welding outdoors, too much gas can actually draw air in, contaminating the weld. Your stick-out is also a bit high, keep it under 1/2" and use a slight push angle.Since aluminum is a great conductor of heat, you may want to pre-heat the 1" square before welding.It will give you a better bead, especially the start.JohnA few weldersA lot of hammersA whole lot of C-clamps