First aluminum welds - washing out at end of run

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I went and ran a whole bunch of beads on aluminum yesterday. Maybe 50.3/32" 2% lanthanated sharpened#8 cup15cfh w/ CK gas saver setup3/32" 5356 filler76% balance120Hz150A, but working the pedalmaterial in the 5/32"-3/16" range, some 6061, some unknown4"-8" couponsAs you might expect, some beads sucked, some were OK as I learned how it responded to heat and filler. But without fail, almost every bead washed out at the end as the coupon saturated and I ran out of heat sink. If I stopped halfway along the coupon (e.g. as I did a few times when I ran out of filler) the finish looked nice and I tapered off on the pedal and dabbed a bit extra and got almost no cratering. But at the end of the coupon, it would spread wide and wash flat.Compared to steel, where you can very gradually taper off and it's nice and linear, aluminum felt much more finicky in that if I tapered amps too fast it would extinguish the arc and I wouldn't fit in extra dabs before the puddle froze but if I tapered too slow the puddle would just wash right out because I was lingering too long and each dab would just fill the increasing, flat puddle.Any secrets to this? Maintaining a clean, regular bead right to the end of a piece of material?
Reply:More amps. 150 amps is about the minimum we use with students on 1/8".  I prefer to set the machine to at least 180 -200 amps on 1/8". 3/16" I'd want at least 200 amps if not more.More amps means you get the puddle going faster and don't heat soak the plate as much. It sounds backwards, but more amps equals less heat input. Faster travel speed would also probably help for the same reason. You can take your time and dawdle with steel. With alum you need to fly. More amps to give you a faster puddle and more travel speed will prevent the piece from getting heat soaked and giving you issues near the end.I'd say the solution to most alum tig problems new guys have comes down to going faster and using more amperage..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:200 amps on 3/32" tungston?  How long before it burns back?30+ yrs Army Infantry & Field Artillery, 25 yrs agoMiller 350LX Tig Runner TA 210, spool gunLincoln 250/250 IdealArcESAB PCM 500i PlasmaKazoo 30"  vert BSKazoo 9x16 horiz BSClausing 12x24 lathe20T Air Press
Reply:Yeah at that amperage 3/32" doesn't hold a point long. Lanthanated would ball up pretty quick. However I regularly use both 3/32" 2% Lanth or 1/8" 2% Lanth at 180 amps without any major problems on my Syncr 200 doing 1/8" alum. The 3/32" balls faster and a bit more, but it gives me a slightly tighter arc. With his adjustable frequency, he'll probably do a bit better than I do. At 200 3/32" balls a lot more, but it's still less than say if I welded with 1/8" pure at the tech school on the Syncr 250's at between 150 and 180 amps.Remember you aren't welding at 200 amps full time. You give it a fast blast to form a puddle and back down right away and fly. Most of the weld once you get the puddle going is probably less than 150 amps..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:I thought of the more amps rule. I'm using a 200dx so 200A is my upper limit. But with 150A @ 76% I was getting a puddle within 2 seconds, which was the other rule of thumb I remembered.Also, I was travelling a lot faster than I would on steel anyway, and feeding filler was getting close to my weak limits to keep up at times. I was feeding about a 1/4" or maybe 1/3" at a time. If I went up 50A I'd be racing. But I'll give it a shot for fun.The other thing was I wasn't even using that much, feathering the pedal. If I stomped the whole time, the bead would wash flat much sooner and go dull and grey no matter how fast I shoved filler in. To get a profile I had to feather it somewhat. If I went too low then sure, I'd be too cold but the ones that ended up how I wanted were surely not at full 150A the whole way.But I'll try pushing it up. I ran out of gas so need a refill first.I think I've got some 1/8" tungstens. I can try those but 2% lanth at 76% balance should be OK at 200A I think?
Reply:Thanks Doug.  Spent a little time on 1/4" alum coupon at 125 amps 3/32" 2% thoriated this afternoon. Got decent beads but somewhat wide due to heat.  Guess I should have been using 1/8" and 200 amps but only had a few minutes to practice and didn't bother changing tungsten.  30+ yrs Army Infantry & Field Artillery, 25 yrs agoMiller 350LX Tig Runner TA 210, spool gunLincoln 250/250 IdealArcESAB PCM 500i PlasmaKazoo 30"  vert BSKazoo 9x16 horiz BSClausing 12x24 lathe20T Air Press
Reply:Originally Posted by metaljongI thought of the more amps rule. I'm using a 200dx so 200A is my upper limit.
Reply:Posted while you were posting. OK, got the 200A early stomp thing.Another interesting thing I tried was I went to a different piece of scrap and tried pulsing. 160A, 100pps, 75% high, 40% background. Apart from the noise, I got weird super wide cleaning. So after I set the pulse to 120pps (weird out-of-sync noise with 120Hz AC/100pps pulsing) I tried pushing the balance up. I got as high as 90% balance and it still cleaned wide. I went back to my coupons and it turned out the cleaning was just an artefact of the scrap I happened to be on. The coupons cleaned (almost) the same with no pulse 76% balance/pulse 76% balance/pulse 90% balance. Initially I had thought that maybe the agitation of the pulse gave extra good cleaning and you could push the balance up, giving better penetration for a given amperage due to more EN time.
Reply:Originally Posted by DSWStoreman on 1/4" I'd want to be even higher, say up in the 250 amp plus range and you will definitely need big tungsten's.
Reply:You are a bit stingy on the gas. So am I but you might want to try 20 cfh.  Default settings are pretty darn good. Look them up in the manual and go from there.Good to hear your machine is working good.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:Yeah, it doesn't help that I weld outside and the wind blew the shielding away a couple of times. I quickly worked out aluminum likes good shielding much more than steel.My favourite part was when someone arrived in the street and our 140lb dog went nuts barking right next to me mid-run. I don't quite have the full relaxed zen approach when welding and flinched heavily under the hood. Touchdown! Pop! Spark! Flash! and a very, very messy pause in a bead.I'll see what happens bumping up the flow a bit and dsw's hot start method after I get more gas on Saturday.