Machine Setup for MIG Aluminium
Shielding Gas
Welding grade pure argon is required to MIG weld aluminium, as opposed to the argon/Co2 mix used for carbon steel welding. Aluminium requires this different gas because Co2 is a reactive gas that reduces the cleaning action of argon that is required to MIG weld aluminium effectively.
Torch Liner
Since aluminium wire is soft, the torch liner needs to be changed to a teflon or plastic liner. Liners are torch specific, so find the aluminium liner for your torch setup.
Contact Tips
There are contact tips made specifically for aluminium that have a large internal chamfer. This reduces the likelihood of the wire catching or jamming on its way out. It is also possible to use tips that are one size above the wire diameter to compensate for this, though obviously this runs the risk of poor electrical contact between the tip and wire.
Drive Rollers
MIG drive rollers come in three main varieties: V-groove, U-groove and ribbed. V-groove is used for mild steel wire, U-groove is used for aluminium, and ribbed rollers are used for flux-cored wire. The U-groove drive roller is required for aluminium as the wire is very soft and will deform as it is being fed through the roller. The U-groove keeps the wire roughly circular as it deforms.
Torch length and coiling
Aluminium wire being very soft is prone to ‘bird nesting’. This is when the wire buckles before it is guided into the torch liner, and wire simply fills the machine case rather than feeding through the torch. Reducing the feeding force required is done by reducing the length of the torch (typically 3 meters), and trying to keep the cable as straight as possible.
When longer torch lengths are required, typically a spool gun is used. Spool guns are a mini wire feed mechanism in the torch itself, which sidesteps the issue of pushing wire too hard through the liner.