Setting Up for Aluminium Welding
Aluminium welding is possible with just about any MIG welder, but aluminium wire is much weaker, more sticky, and expands more than steel wire so you'll need to take a few steps to set up the welder to prevent wire feed problems.
Well worth bearing in mind that MIG is only sensible for thick aluminium. AC TIG makes thin aluminium welding very easy, so the set up on this page cures a problem that doesn't need to exist. Though not everybody has an AC TIG. I know I didn't when I wrote this page.
Crumpled Aluminium Wire!
Aluminium wire is much softer than steel wire. I took a photo of my first aluminium welding experience. The wire folded up in the wire feed as soon as I struck an arc!
This was very frustrating and you'll find a few posts in the forum about this and the rest of my learning experience. The main problems were down to the wire liner and tip.
There are a couple of reasons the wire crumpled up in the rollers. The first is that aluminium expands much more than steel when it gets hot and seizes inside the brass tip.
The way around this is to use an oversized tip. I used a tip designed for 1.0mm steel wire for running 0.8mm aluminium wire.
Plastic Wire Liner
Aluminium wire is "stickier" than steel wire and will tend to pick up on a steel wire liner. Replacing the steel liner with a plastic one seems to get around this problem. Teflon liners are recommended.
I've extended the liner as close as possible to the wire rollers to reduce the distance the aluminium wire needs to travel unsupported. Halving the distance between the rollers and the liner will quarter the chances of the wire crumpling up.
Pure Argon Gas
The final step is to arrange a supply of pure argon shielding gas. The photograph shows a small 60l gas bottle connected to the gas hose via an imperial brake pipe fitting (naughty).
These bottles last for about 1 metre of welding, and I got through three of them in my early stages of practicing before deciding a full sized bottle would be much more economical.
The wire feed speed for aluminium welding is about twice that of steel welding with the equivalent diameter wire. That means you can use a thicker wire for aluminium. A thicker wire will be less prone to birds nesting. Use 1.0mm diameter aluminium wire instead of 0.8mm wire.
Wire Roller Tension
The roller tension can be vastly reduced as the rollers will grip the aluminium wire much better than steel wire. Excessive tension could cut a sharp edge into the wire which might wear through the wire liner and increase friction. Rollers with "U" shaped grooves rather than the standard "V" shaped grooves are available and would presumably reduce this problem.
The set up above, combined with a straight as possible welding cord should result in a reasonably good wire feed for aluminium welding.