Sooo? I have a miller welder with an aluminum spool gun. Im welding .09 aluminum to a much thinner guage aluminum. I am very good at welding steel, but I keep burning holes in the aluminum. I have turned the gas way up and turned the heat down. I cant find a happy medium. Do you have to run your beads faster or what or do I need to slow my wire speed down. any help?

120 volt or 220 volt? anything thinner than .09 with a 220 mig is a waste of time. How thin is the other piece?

the only tip I have for you is clean each piece with a stainless brush immediately before welding, but I think you're probably SOL. you can turn your wire speed down all the way, on the lowest setting and lay a bunch of overlaying tacks, or just have it tigged.

Tig!

IMO a spoolgun on thin aluminum is an exercise in frustration, Find a tech school of friend with a tig welder

I have access to a tig but haven't tig welded since high school. My miller is a 220. any tips for tig welding. I think the other aluminum is .053 or so.

I have just started welding aluminum with my miller 180 autoset and spool gun. I use a stainless wire brush before welding as mentioned. I use mine for repairing my aluminum boats and adding decks, etc. The thinnest I've welded is .080 ga. I have no problems with burning through. On mine, I have to turn the wire speed really high---like near the 90 mark. The autoset doesn't work at all for me on aluminum. If the metal has absorbed grease or oil, or is dirty in any way you can't possibly weld it.
I've had better luck with Lincoln superglaze as far as making better looking welds. I recommend using .035 tips even with .030 wire to prevent sticking, but I'm no expert by far. Of course I'm using 100% Argon as I'm sure you're doing as well. THere are some videos on youtube of guuys welding aluminum that I found helpful.
Later,
JBJ

Thanks, once i cut the aluminum i will have plenty of scrap metal to practice on. Well I will take pics of my crappy tig welding job when im done. ha ha ha

Y'all going into the spray arc when you mig the 1/8 th alum?

With aluminum you need to hand clean with a stainless brush, a power wheel will just smear the oxide into the surface and leave you with a dirty weld that doesnt flow well, follow the brushing with an acetone wipe and wipe your filler rod down as well.

With the aluminum mig, there is no way you are going into spray transfer, it may resemble spray but it isnt. Its most likely globular transfer, Mig is not an ideal process for welding aluminum, especially thinner material. It works well on thicker stock (1/8" and up) but you usually end up with a cold start and a lot of post weld cleaning to get rid of all the smut left behind.

Welding aluminum is always done with either pure argon or an argon helium mix gas, rarely on thick parts you will see pure helium but with newer machines coming out that is getting very rare

Thanks indawoods