Id say most machines will weld aluminium if set up correctly but obviously the better the welder the better the weld. I have three migs that are more than capable of welding aluminium. A Cebora 2035m Pulse, a Cebora 2020 synergic and a Lincoln Electric Powertec 360. These arent cheap machines new but I got them all at good prices second hand. There are many more migs out there and im sure someone will be along to confim but I have only used these for ally so cannot comment.
That 'someone' isn't me but let's have some more info please. What thickness of Aluminium do you intend to weld?
You will need to use pure Argon as your shielding gas.
Do you intend to use a Spool Gun?
If you are welding thin sheet, and you have time to learn, I would suggest a quality AC Tig welder machine, but please give more details and wait for the experts to reply.
i know that i need pure argon or argon + helium or pure helium to get best penetration on aluminium
tough i never used a spoolgun, this device can be connected to a tig inverter?
minium thicknes i would like to weld starting 2milimeter i have no problems welding thicker material with proper preparation as i am used welding stainles steel and other types of steel
mybe cheap welder wont do it,
probaly something like a TELWIN BIMAX 4.135 TURBO might be a good match starting from 399 euro nice compact mig welder
Unfortunately you can only connect a spool gun to a MIG power source, several good guns out there, but the good ones are dear.
Camarc did some nice smooth sets with the SP3 gun which can be picked up very cheap these days. Got a few still left myself. Failing that you're looking at buying a mig with the best feed system you can find if you want to tackle ally on a regular basis. Anything with 4 geared rollers is a good start, less tension needed to push the wire as you have twice the traction of a 2 roller drive so the wire won't wrinkle so easily. Sort out a Teflon liner (with a brass neck as you can't run plastic liner all the way to the tip on an air cooled torch, not if you intend to weld for long at high amps as the liner will melt in the swan neck) and some ally tips and you're away.
Sets with good characteristics on ally and good drive systems can be found from the likes of EWM, Fronius, ESAB, Lorch, Merkle, Lincoln and Miller, plenty of others but all the above make sound investments second hand (if looked over carefully before buying)
It's worth bearing in mind that just about any old mig will do a reasonable job on steel, getting ally right is a lot tougher unless the set is dialled in and feeding reliably.