[tweake]

Thanks tweake & VA-Sawyer
- the cleaning (DC offset) can be set from 0 to 50% on this machine, I tried from 25 to 35%
- changed the electrode for a 2.4mm @ 140A, with a #10 collet, tip does ball, but not much
- the coupon are scrap from the shop down the street, brand new, they solder it daily, but no idea what is it.
- filler is 2mm AlMg5, that's what the same shop recommended
- torch angle regular 45/50°

The puddle is shiny in few second, but there is always a black smear on the middle, not going on the sides, even without filler.

i would get the torch angle a lot more vertical ie 10 degrees.
but other than that i would suspect the aluminium. maybe thats why they solder it instead of weld it.

[Tweepy]

i would get the torch angle a lot more vertical ie 10 degrees.
but other than that i would suspect the aluminium. maybe thats why they solder it instead of weld it.

Ok for a more vertical torch, will give a try.
Solder > meant welding (TIG), sorry, I'm a electronics engineer, kinda more used to this term.

Otherwise I'm suspecting the gas shield, as from my very first welds with this machine (few posts above, they look good), everything was very clean, but meantime, I had to change the bottle/regulator as it was lent to me: maybe this new one is off, or contaminated?

[VA-Sawyer]

You said DC Offset, I'm not sure you are adjusting the correct thing. Cleaning action refers to the percent of time that the AC waveform is positive. You can't have an AC wave with 0% positive time.
I am beginning to think your machine can do "mixed mode" tig.
That means the current is AC for a shot time, then DC , then back to AC. This allows more heat input for a given current. Useful on thicker Aluminum.
The sound should be a constant tone on AC. No changes in loudness or frequency while welding. Make sure you have the CLN led lit to set cleaning action.
Make sure the gas is 100% Argon.

[tweake]

couple of other things,
tungsten grind, it looks like you have a fine taper. with aluminium you want the opposite to what you have for stainless. make it look like a crayon, quite a blunt taper.
the other is the snot hanging off the filler. cut that off as that can blow up as you feed the filler and containment your tungsten.