Sputtering in AC mode

I have a 250ex. Been welding steel and machine running perfect. Today I decided to weld aluminum here is where the problem starts. Welds fine but when I back off the pedal to finish the weld it sputters and pops and won't hold a stable arc. This seems to happen about 20 amps or less. If I start with low amps it sputters then also. Below is some things I have tried
1. Sharpened tungsten properly made a mirror smoothe finish
Also left rough finish same results
2. Ran from 8 to 30 scfh. No help
3. Balance and hertz different setting no help
3. Ground directly to work price. No help
4. Changed torch parts. No help
5. Cleaned metal acetone stainless brush. No help
6. Gas is flowing from torch as it should
7. Argon is down to about 750 lbs.
machine is about 2 weeks old. Welds steel just fine down to minimum amps
High freq . works every time. Any ideas???

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Originally Posted by Chevelle69

I have a 250ex. Been welding steel and machine running perfect. Today I decided to weld aluminum here is where the problem starts. Welds fine but when I back off the pedal to finish the weld it sputters and pops and won't hold a stable arc. This seems to happen about 20 amps or less. If I start with low amps it sputters then also. Below is some things I have tried
1. Sharpened tungsten properly made a mirror smoothe finish
Also left rough finish same results
2. Ran from 8 to 30 scfh. No help
3. Balance and hertz different setting no help
3. Ground directly to work price. No help
4. Changed torch parts. No help
5. Cleaned metal acetone stainless brush. No help
6. Gas is flowing from torch as it should
7. Argon is down to about 750 lbs.
machine is about 2 weeks old. Welds steel just fine down to minimum amps
High freq . works every time. Any ideas???

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I have this problem also and have tried all of the above. He machine welds fine but arc is unstable at lower amps. I was thinking its a foot pedal issue and plan on getting the USA made pedal.

Just for kicks I used the torch switch and set the up and downslope to mimic what I was doing with the foot pedal.
Same problem!!!

Try this

When using foot pedal set start amps and end amps to ZERO

Some time I forget to do this if I have been using torch switch

And I forget to reset when switching back to torch switch

IF your 250EX is points model check point setting inside. The manual has settings

All settings for torch switch are at zero. As I said the hf starts fine every time. It's just when I back of and get down to less than 20 amps it sputters. No way I can weld at the low end it is rated for. Haven't checked the points does the control panel and rear panel have to come off to get the cover off? It looks like they do. Machine works fine except for the low amp thing.

It all depends on what you mean by sputtering. If you mean that the arc is unstable and wanders around, that is almost always caused by too low current for that size tungsten. Don't expect a 3/32" tungsten to weld nice at 10 amps, cause it just won't. If you want a stable arc at 20 amps, an .040" tungsten would be best, and 1/16" ground to a needle would be second choice. Anything bigger won't get hot enough at that current. Points are only for the HF start, so as soon as the main arc is going they do nothing. As long as you are getting good HF starts, the points are doing their job. Low amps on aluminum is a bit tricky and does take some practice. Keep your arc length as short as possible. A good rule of thumb is to shoot for about one tungsten diameter. Make sure your cup is large enough to shield your weld pool and the cleaning area. About 6x tungsten dia. is a good start. Too much argon is just as bad as too little. Set the flow based on cup size and be sure you are not mixing up CFH and LPM. Different flow meters have different calibrations, so make sure you know what you have. Make sure you don't have a breeze where you are welding and watch out for excessive torch angle. All kinds of things make a lot more difference for low amp aluminum. Steel is about the easiest, then stainless, then aluminum, and the lower the amperage the harder and less forgiving it is. Things you can get away with on steel you can't on aluminum, But it will make you a better welder on all materials. If you are working on thin material, you can also move your AC balance to give a little more cleaning. That will cause less penetration so you will have more control. It just takes a lot of practice.

There it is!!! I'm using a 3/32 tungsten on 1/8 material. Welds fine but when I taper to end the weld it kinda pops and sputters if I taper way low. If I don't taper amperage all the way then terminate its fine. So what your saying makes perfect sense. The problem is not the machine it's behind the hood. LOL.
So if I use a smaller tungsten I should be able to go lower in amperage without all the sputter.
BINGO!!!

I have a new (2015) 255EXT and it does the same thing, just not all the time. The problem with it being the tungsten size is if you are using 3/32 tungsten on 1/8" material and your trying to tapper off to prevent a crater crack it starts popping violently. It's a strange popping almost like the arc is going off and on. I'll try again tonight and see how low it will go, with 3/32, 1/16 and .040 and see if it makes a difference.

I have a question regarding the HF points gap. Do these new machines have points? I thought they were solid state.

Exactly what mine is doing. Looking forward to your results as I only have 3/32 at the moment. Going to the lWS today to buy other sizes.

Popping violently is something else entirely. Can't fathom a guess without more information. I believe the digital machines are solid state HF and the analog are points.

When starting at low amps say just starting the arc it seems as if the arc jumps back into the cup before it goes to the workpiece. As you add more amps the arc stabilizes with no more popping. As I back off the amps to prevent craters say the last inch of pedal it starts the popping again. As I've said I've tried it with the torch switch using up and down slope to mimic the foot pedal amperage and the same thing happens. About 18 amps is as low as the machine will weld without popping. If I do any of this on DC the arc will stay perfect down to 6amps.

Quote:

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Originally Posted by Chevelle69

When starting at low amps say just starting the arc it seems as if the arc jumps back into the cup before it goes to the workpiece. As you add more amps the arc stabilizes with no more popping. As I back off the amps to prevent craters say the last inch of pedal it starts the popping again. As I've said I've tried it with the torch switch using up and down slope to mimic the foot pedal amperage and the same thing happens. About 18 amps is as low as the machine will weld without popping. If I do any of this on DC the arc will stay perfect down to 6amps.

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When starting that is about right, if you start too low it will wander, that is when the tungsten is cold. Raising the starting amps a little should give you a crisp start. However, once it's hot there should be no problem in doing a normal taper at the end of the weld, so you have something else going on. What are your machine settings and arc length? Without being able to see what you are doing it is difficult to see if you have a problem with technique. If it welds fine with higher amperage, that rules out a lot of things.

Max amps 125
Pre flow2sec
Post flow 10 sec
Frequency 120 hz
Balance 35
Gas at 20 scfh
3/32 2% lanth
All other setting off
Tried various arc lengths from 1/16 to 1/4
Torch angle doesn't seem to help straight up and down to different angles

I'll mimic your settings tonight and see what I get. Welding tips and Tricks has a video with the PowerTig 250ex welding bottoms of aluminum cans comparing to the Dynasty and he's only using 11 amps and it's welding great. He doesn't say what size tungsten.


"How to Tig Weld coke cans with a miller dynasty 200dx and an Everlast powertig 250ex, good tig welding settings for thin aluminum are 60 pps, 30% t and 20% background current. 60% ac balance, and 90hz frequency worked out ok.
Low amperage starts on both machines allow arc starts with no holes blown."

Looking forward to your results. Thanks for taking the time. I've seen that video that's why I was wondering what's up with mine. The only thing I can think of if its not the machine I was welding in my shop at about 40 degrees with snow melting and high humidity inside. Maybe the aluminum was pulling in moisture. I don't know. Machine is fine other than that sputtering at very low amps. Doubt I will be welding coke cans but if the machine is supposed to weld that low I want it to be able to.

I tried it with the 3/32, 1/16 and .040. It popped on all of them. But I'm beginning to think it may be the metal. I was using .125 thick aluminum. After the metal heated up it seemed like the popping subsided. I was backing the pedal all the way off, the arc would start to wonder and wouldn't come off the tip, and only popped if I held it like that for a second or two.

I tried the coke cans several times and only managed to melt the cans. I couldn't get a decent arc even with .040. Another thing, your wasting argon with a 2 sec pre. You only need about .5 and post around 7 sec. Unles you're doing some odd joint. I'll keep trying to see if it's just me or the machine. I know how annoying it can be.

Thanks for the tip on the pre flow. Can you maintain an ar at about 11 or 12 amps without it popping?
Also does it pop when you ramp down the amps to keep from cratering. I was ramping down almost all the way. Is this necessary. Mine doesn't start popping as I'm ramping down just when I am almost all the way off the pedal.
Thanks again for you time and effort.

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Originally Posted by labmaster02

I tried it with the 3/32, 1/16 and .040. It popped on all of them. But I'm beginning to think it may be the metal. I was using .125 thick aluminum. After the metal heated up it seemed like the popping subsided. I was backing the pedal all the way off, the arc would start to wonder and wouldn't come off the tip, and only popped if I held it like that for a second or two.

I tried the coke cans several times and only managed to melt the cans. I couldn't get a decent arc even with .040. Another thing, your wasting argon with a 2 sec pre. You only need about .5 and post around 7 sec. Unles you're doing some odd joint. I'll keep trying to see if it's just me or the machine. I know how annoying it can be.

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If it welds ok at higher amperage, I really doubt it's your metal. At the end of the weld, the metal will be hot enough to drive off any moisture. The arc not coming of the tip is usually due to the condition of the tungsten. Either it has contamination on it, or there is something sharp that the arc will prefer to jump off of. If you dip the tungsten in the puddle, you need to stop and grind it clean again. With steel you can often get away with rocking on, but rarely with aluminum. Since these are two totally different type machines (digital vs analog) I would guess it's a technique issue. Unfortunately, it has been many years since I trained a new welder, so I don't remember what the common mistakes are and what would be causing your issues. It's very hard to do this without seeing what you are doing. Both those machines should be more than capable of welding cans, but no matter the machine, that takes a lot of skill and practice.

It seemed like when I was just trying to start and stay at 10 amps it popped like crazy. If I ran a bead and tapered off it was fine, but if I continued to hold low amps for a few more seconds it would start popping occasionally. There's no need to hold the low amps for that amount of time though. As a note the tungsten was clean and for the most part polished just to make sure. For the cans it appears they need the oxide or coating removed. I tried a wire brush scotch brite pad and acetone still the arc would wonder all over and the aluminum would just cave in. I couldn't even get the rod to melt in. I hope it's just lack of experience and will come over time.


I just ran a bead on .050 aluminum, 3/32 tungsten, 1/16 4043 rod, 55amps, 120 Hz, 25% balance. I first started with low amps and tried to hold it and it popped. I then ran a bead, floored the pedal ran about 2" and tapered off to nothing. It worked great, no popping.

Thanks for all the input. I'm going to try with all the suggestions from here tomorrow. I'll report back with how it goes.