I have done some amount of aluminum welding with about 4 or 5 different setups. My take on it, A spool gun is a good get you by as mentioned the wire can have a tendency to deform as it reaches the puddle and be a real pain, positioning and angle are a big player in this also if the welder is capable changing the pulse width can help tremendously this is something you just have to play with. Used or dirty material is the worst for a spool gun.
I haven't done much tig welding, have one sitting the corner same as new but I find for myself that I'm much more skilled using other methods and the "look" of a tig weld doesn't make me all super excited like it does most people, just glad I can do it and obtain satisfactory results.
The best I have used is the push pull style, current setup is a Miller 350P dedicated to a 30' Python gun. The gun/whip cost as much as the welder! But it works great not as picky about material and leaves a much nicer higher quality weld, its more akin to using a regular mig. The major advantage is the adjustability of the welder itself, its more than just amps and wire speed, the same spool gun will provide much better results used on such a welder as compared to simpler/cheaper welder.
Remember if aluminum has been in contact with oil to preheat to try and remove as much soaked in oil as you can, and NEVER weld aluminum with oil in direct contact with oil, for example an aluminum oil tank with out first draining and cleaning excess oil out, It can cause an explosion.
Snap-On welders are a Systematics, a cheaper but still good welder, I have been around about 4 of these. I used to hate and cuss them until one day we replaced the whip on one with I think Miller. It was an entirely different machine to say it made it better would be an understatement. Ended up replacing the whips on a few of the others and it made the same improvement. I recommend if anyone has a Snap-On/Systematics to replace the whip with a quality one from Miller or Bernard it will make it better then it was brand new!
