sheet metal welding certification (MIG)

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I am an apprentice in the local 104 sheet metal union and am currently in the programs welding class. Some of us are going to begin preparing and practicing for our (MIG)overhead certs. I believe it will be on 16 or 18 ga. galvanized sheet metal.Most of my welding has been on 1/8" or thicker and not too much galvie at allSo I was wondering if you could give me any advice on setup ,voltage ,amperage (ipm), technique for overhead and anything else I should know . The machines we will be using are Miller XMT's  and sometimes Lincoln sp-100's and .030 wire , and 75-25 gas.Thanks for the help,Rich
Reply:I have a D1.3 cert for structural galv sheet steel.   The test was 3G and 4G on 16 ga galv steel sheet, open gap butt welds on 6x6 coupons.   I did the test with my Passport mig and .035 E71T-GS self shield fluxcore wire.   I used the same machine and wire on the job, which was welding the galv steel framing on school buildings.   The Passport doesn't read in volts and inches per minute and I never used the XMT on that job.  My settings would be different for fluxcore than solid wire and gas anyways.  A place to start would be 16 volts and 150 ipm, if you're welding on 16 ga with .035 solid wire and 75/25 gas.  Use a little higher wire speed setting for .030 wire.Last edited by DesertRider33; 09-19-2009 at 06:41 PM.MM350P/Python/Q300MM175/Q300DialarcHFHTP MIG200PowCon300SMHypertherm380ThermalArc185Purox oaF350CrewCab4x4LoadNGo utilitybedBobcat250XMT304/Optima/SpoolmaticSuitcase12RC/Q300Suitcase8RC/Q400Passport/Q300Smith op
Reply:Ok so I haven't taken my certification test yet but I have been practicing. At school I have been running 14.5 volts and my wire speed is set around 145-150. I know that I am getting full penetration but what I am concerned about is the bead height. The bead is narrow which I believe is ok (can be 2-3x the thickness of base metal right ?) but it just seems alittle high to me. Is that just typical of overhead welding ? What should I try to do to flatten it ? I just run a straight stringer no weave and in a drag type motion. please helpRich
Reply:Turn up the voltage a little and/or turn down the wire speed a little.MM350P/Python/Q300MM175/Q300DialarcHFHTP MIG200PowCon300SMHypertherm380ThermalArc185Purox oaF350CrewCab4x4LoadNGo utilitybedBobcat250XMT304/Optima/SpoolmaticSuitcase12RC/Q300Suitcase8RC/Q400Passport/Q300Smith op