Aluminum Mig Overhead

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Looking for some opinions here. I have a lot of experience welding aluminum and do it frequently. Recently, I was doing some welding on an aluminum trailer. I was welding 1/4" aluminum tube to 1/4" aluminum angle. My problem was in the overhead position the results were disastrous. Welding flat, as usual, was not a problem and produced great results.My question is, is there an operator error here that I am not getting in doing overhead aluminum MIG? I have a Lincoln 350MP and Prince XL spool gun with 3/64" 5356. I don't recall the settings I used but I used the same settings I welded in the flat position.Any comments or suggestions would be appreciated.
Reply:Based on my own experience with a Lincoln Pro-MIG 175 (no spool gun) on aluminum.    For the brief overhead welding, I turned up the heat higher than necessary, but kept the wire speed consistant with what I would have used for a vertical down.   The trick was to limit the bead length to basically tack welds.  The end result resembled TIG welds more so than MIG.  I can't attest for the quality of the welds, but for that application, those welds were not that critical.    I also had to weld from underneath a welding blanket to keep from getting peppered with molten aluminum.    Since then, I've avoided any overhead welding.Where I work, all the aluminum welding, robot or manual, is structural.   The welders invert whatever they're working on (regardless of size) to have either flat or vert down welds.There are no small projects
Reply:Where you using stright MIG or pulse?My PicturesLA 4x4 Forum
Reply:Straight Mig - 100% Argon
Reply:Originally Posted by imagineerBased on my own experience with a Lincoln Pro-MIG 175 (no spool gun) on aluminum.    For the brief overhead welding, I turned up the heat higher than necessary, but kept the wire speed consistant with what I would have used for a vertical down.   The trick was to limit the bead length to basically tack welds.  The end result resembled TIG welds more so than MIG.  I can't attest for the quality of the welds, but for that application, those welds were not that critical.    I also had to weld from underneath a welding blanket to keep from getting peppered with molten aluminum.    Since then, I've avoided any overhead welding.Where I work, all the aluminum welding, robot or manual, is structural.   The welders invert whatever they're working on (regardless of size) to have either flat or vert down welds.
Reply:I pulled this off the Lincoln website and found it interesting and somewhat applicable to my situation.  What's the deal with Pulsed MIG Power Supplies? What is the advantage over traditional CV Machines?For aluminum, the goal of pulsing is to have the ability to use spray transfer while minimizing heat input. This makes pulsing especially suitable for thin aluminum – say ¼” or below. While it is not wrong to use pulse welding for much thicker aluminum, pulsing begins to lose its advantage.Pulse welding out-of-position is also much easier than spray transfer out-of-position welding. And it is much easier to learn to weld aluminum using pulsed transfer because the arc is more controllable.In pulsed spray transfer, we pulse the current between a “Peak Current” that is above the transition current and a much lower “Background Current”. We have spray transfer when the arc is above the transition current. When the arc is at the Background Current, no droplets are transferred.Pulsing occurs several hundred times per second. Therefore, we get spray transfer at a much lower average welding current so that we can easily weld thin aluminum.
Reply:When I am welding aluminum overhead (pulse) I also turn my wire speed up a little and depending on the situation I might turn my heat down some too. I usually move a lot faster also.My PicturesLA 4x4 Forum
Reply:Could gas flow be the issue?  argon is heavier than air and all.  noob question.Various GrindersVictor Journeyman torch200cf Acet. 250cf oxygenLincoln 175 plus/alpha2 gunLincoln v205t tigLincoln 350mpEsab 650 plasmaWhen you can get up in the morning, Its a good day.Live each day like its your last.