Welding aluminium can be very satisfying or a real pain. The one thing that will make the difference is getting the right welding machine and the welder setings right and practice practice and more practice. This is not a complicated explanation it is an easy to follow guide to get you Tig welding aluminium.
Mig or Tig ?
Mig is hard to use on aluminium compared to welding steel which is a breeze. It requires a gun that pulls the wire instead of the machine pushing it to avoid wire tangles. It is messy with lots of fumes and sparks. But it is quicker if you get it right. The weld however even with pulse mig is not as neat as Tig. Pulse and double pulse synergic machines are becoming common and have very little spatter and much less fumes. These machines can be quite difficult to set up even though the wire speed and amps are set by the machine. The weld is hot and travel speed has to be much quicker than Tig. Also a pull gun is a required to stop bird nesting.
Tig gives a clean fume and spark free weld. It also gives a much better looking weld. The key with Tig welding is getting the settings right, now with pulse and digital machines there are untold dials and buttons to play with which can cause confusion.
As for pulse i don't like it generally. For normal material thichness of 2mm and above normal mode is fine. One thing that is really helpfull is a amp adjustable torch so you don't have to get to the machine to change the power setting.
Basic settings to get you welding:
Amps: 40 per mm, its much better to be too hot, the aluminium should transform to a wet looking spot quickly. Too cold will take ages to get a wet area and will drive you mad. Once the spot in front of the torch looks wet feed in a small amount of rod it should melt imediately into the puddle, continue feeding rod and move the torch forward. That's it your tig welding.
AC frequency: is available on most modern machines the higher you turn the frequency the louder will be the sound and the more tight and precise will be the arc. Turn it up to start with it will make things much easier.
AC balance: puts or reduces the amount of heat in the electrode, and the amount of cleaning action of the work piece. The percentage on the dial or read out varies with machine brands. But generally a lower percentage puts more heat into the metal and less in the electrode. If the electrode balls too much or blows itself apart theres too much heat in the electrode. Put as little heat as possible into the electrode to start with, this will also give you maximun cleaning.
Gas: this can be a problem too, use plain Argon and as little as possible. Every one has a volume that they reccommend. I have found most regulators are not very accurate when the volumes/flow get low. I normally listen for the gas hiss at the torch, if you can hear a very slight hiss you should be ok, the guage i use shows zero flow or a slight flow. If you get black soot or a black pepper speckle increase the volume slightly. Too much gas will just waiste your money very quickly.
Pulse: turn it off.
Any other dials turn to zero to start with.
Cleaning the work piece: If the aluminium is new all you will need is the AC cleaning from the machine. If its old and dirty clean it with a stainless steel brush then any commercial aluminium cleaner (phosphoric acid)and lastly acetone, nothing else.
Check out www.weldingtipsandtricks.com website this guy really knows what he's talking about.