Fine tuning settings for MGAW aluminum

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I can MIG weld 1/8" to 1/4" aluminum with no problem, however I've been having some issues getting the settings right on thicker aluminum. Welding a large fixture comprised of 1-1/2" thick aluminum plate, 36"x36" with a grid lock on top of 3/4" thick aluminum plates. Using a Miller Pheonix 456 (same as XMT) with an XR-A feeder cabinet, and 30' XR-A pistol grip gun with 10" barrel extension. From what I've gathered so far, Argon CFM should be around 40-50? Always push when possible, and keep spray about 1/2"-3/4" long. Miller says to use 1/16" wire, but I'm using 3/64" 4043. They also recommend 30 volts and 300 amps at 1/2"+ thickness aluminum, but that may be too much for the wire? Jody from welding tips & tricks has a video of him welding 3/4" thick aluminum with .035" wire.  How do I know if I need to turn up or turn down the gas flow? My biggest question is how do I know if I should turn up the volts, or lower the amps?John 3:16(2) Miller Pheonix 456(2) Millermertic 252Dynasty 210DXHobart 210MVPDoringer D350 SA Cold SawScotchman 350LT Cold SawWebb 10x50 MillWebb 15x40 LatheGeka Bendicrop Ironworker
Reply:When mig welding aluminum you will know if you need to turn the volts up because the arc will make a crackle noise and start creating spatter, also if you wire feed speed is too high it will do this as well. I run a nice spray where there is almost no noise and you can see the puddle wetting in very nicely.
Reply:4043 is junk, and you will get little to no base metal dilution into the puddle of which 4043 is dependant. Switch to 4943 or 5356 and the magnesium will add some exothermic reaction to the arc. You can also go with a mix of 75ar/25he for a hotter arc as well.We use 3/64" wire as well on 1" and it burns smoothly. We use the hot start feature at the beginning of the weld as there is where lack of fusion takes place. PM me tomorrow and I can have my girl pull the settings. From what I remember she is using 25 volts.Weld like a "WELDOR", not a wel-"DERR" MillerDynasty700DX,Dynasty350DX4ea,Dynasty200DX,Li  ncolnSW200-2ea.,MillerMatic350P,MillerMatic200w/spoolgun,MKCobraMig260,Lincoln SP-170T,PlasmaCam/Hypertherm1250,HFProTig2ea,MigMax1ea.
Reply:Originally Posted by puty72When mig welding aluminum you will know if you need to turn the volts up because the arc will make a crackle noise and start creating spatter, also if you wire feed speed is too high it will do this as well. I run a nice spray where there is almost no noise and you can see the puddle wetting in very nicely.
Reply:It won't be too much for the wire. Porosity becomes an issue when the puddle gets too big, or the cone gets too long. The larger wire allows more amps, but you can use lots of wire feed to make up for larger diameter.Constant Current Weldor.