Our Air Liquide M200 welder has served us faithfully since we acquired it over a year ago. During that time,

Capabilities: Weld output range of 300 A at 60% duty cycle Weld steel wires up to 1.2 mm (0.045 in)* Weld aluminum wires up to 1.2 mm (0.045 in)* * Dependant upon amperage capacity of power source. Features and Benefits: Adjustable nozzle Allows operator to adjust contact tip to nozzle distance for short arc and spray applications Internal gas line connections Longevity of gas line Light-weight Reduces operator fatigue Compact Increased operator comfort 6.0 m (20 ft) cable connections Allows access into hard to reach areas Accommodates both mild steel and aluminum 102 mm (4 in) spools Versatility Connects directly to M 200 and M 250 welders Convenient, does not require external controls to operate

we've welded axle brackets, rocker armour, bumpers, and built a complete pickup box from scratch. It's been an extremely useful tool but the addition of the SG300 spool gun has made the M200 even more versatile because we can now easily weld ALUMINUM!

It's true that steel is much more useful when fabricating 4x4 stuff, but aluminum's light weight and corrosion resistance provide distinct advantages which make it preferable to steel for some projects. Skid plates, cargo racks, and even bumpers, can all be built using aluminum. If you're building a rock buggy, aluminum can also be used for dash boards, floor wells, fenders and body panelling. Usually these aluminum items are found on competition vehicles (like the afore-mentioned rock buggy) but with the ongoing demand for maximum performance in the recreational fourwheeling world, reducing vehicle weight by using aluminum is more common than ever before.

You can weld aluminum with a regular MIG welder (a flux core welder is not the same thing) but there are two major limitations. First, you need to use relatively stiff and thick aluminum wire. The reason for this is because aluminum wire is very soft and the MIG is trying to push it through a 10- or 12-foot hose. If you don't use the thickest, stiffest wire, the odds are very good that the wire will ball up into what is called a "bird's nest" as the drive wheels try to push the wire down the hose. The other limitation is that you need to keep your wire hose as straight as possible because every bend in the hose causes friction between the wire and hose liner. A single bend is all it takes to create a bird's nest. So for very simple aluminum projects, you can get by with your basic MIG. But for any project that is going to require more than an hour of your welding time, I would really, really recommend using a spool gun.

The spool gun contains its own mini wire feeder that feeds into a very short and straight output tube. That eliminates the two down sides of the regular MIG setup. As an added bonus, because the gun carries the wire, the power cables that connect the gun to the welder can be longer than those used on a regular MIG torch.

Hooking up the spool gun is very straightforward. Simply connect the gas/power line...

then the control cable...

and you're done!

I wanted to replace the heavy steel cargo rack in my Jeep with a lighter aluminum replacement. I also had some other ideas for lighter accessories for my Jeep so I decided to augment my M200 welder with the Air Liquide SG300 spool gun. Its 60% @ 300 amp rating made it a perfect match for the

Click on the image to see a diagram of the SG 300's components.

Ok, so here's how my first attempt at aluminum welding went:

I was working with 1" square, 1/8 " wall tube for the rack and would need to make some angled cuts. Because aluminum would plug up my chop saw's abrasive cutting wheel, I decided to use my mitre saw. I installed a carbide tipped blade that was suitable for cutting a variety of materials, including non-ferrous metals (eg: aluminum) and some wax was applied to the blade to aid in cleaning the aluminum shavings out of the blade during cutting. If you've ever used a mitre saw for cutting wood, cutting aluminum is pretty much the same experience. Once you get over the fear of expecting the carbide tips to shatter when they strike the aluminum, you will really appreciate the quality of cut that you get from the blade. The accuracy of the angles was far greater than what I got with my chop saw.

Here's the carbide-tipped blade I used to cut the aluminum.	Waxing the blade before cutting will help dislodge the aluminum shavings from between the teeth. Although you can't tell from this photo, I powered the blade into the end of the wax tube to coat the teeth.
We used a grinding disc specifically designed for use on aluminum.	Never use your disc or brush on steel! Labelling them makes it easy to remember.

Once I had the pieces cut, it was time to prepare them for welding. Besides cutting the pieces for the project, I also cut up some small pieces for practice welds. Since I had never welded aluminum before, I knew that the first batch of welds would be rather ugly. I gathered these pieces and bevelled their edges with the stainless steel grinding disc and cleaned the surfaces with acetone. Remember, surface preparation is the key to successful aluminum welding! Next, I set up the Air Liquide M200 welder. I attached the AL-TIG gas and removed the torch hose. In its place I attached the spool gun's hose and the small control plug. After loading a spool of wire into the gun, I purged the hose (the M200's purge feature allows me to do this without triggering the welder) so AL-TIG gas would start coming out as soon as the weld started.

Finally it was time to try my hand at aluminum welding. I guesstimated a setting that would've been in the ball park for welding mild steel but it didn't seem hot enough. The bead laid on top of the metal like thick globs of glue. Turning up the power a notch was too hot and blew a hole through the aluminum almost immediately. After some trial and error, I found that the setting that worked best was one similar to what I'd use for mild steel, but with quite a bit more wire speed. Speaking of which, if you adjust the wire knob on the welder in an attempt to dial in your settings, you'll be fiddling with it for a long time. The wire speed adjustment for the spool gun is on the bottom of its handle. Oh, here's one more very important thing to remember when welding aluminum: always angle the gun in the direction that you'll be welding. This way, the gas from the nozzle will blow ahead of the weld to keep the area free of gaseous contaminants. Likewise, when you finish your weld, hold your position for a second before pulling the gun away. The little bit of gas that exits the nozzle after you release the trigger will protect the molten metal.

With the spool gun dialed in, I moved on to welding the actual pieces for the rack. Welding was pretty much the same as with mild steel welding. Cleaning up the weld afterwards with a grinder or steel brush was much easier, though. As the rack took shape, it was also much easier to move it around than steel because aluminum is so much lighter. Working with aluminum was so much more enjoyable than steel that I've already started thinking about other projects I could use it for. I would really like to eliminate some of the steel on my swing out tire carrier in order to make it much lighter.

Notice that I'm angling the torch nozzle in the direction that I'm welding.	The black soot is typical in aluminum welding. If you're getting this soot ON your welds, it's probably because you're pulling instead of pushing. Remember, the gas has to flow forward in the direction that you're welding.	A quick wipe with the wire brush and the weld is cleaned up.
I found it much more comfortable to weld with the spool gun's cable draped over my shoulder.	Working with aluminum is very nice. No back strain when you're handling your work and very easy to dress the welds with a grinder.	Air Liquide www.airliquide.ca

As you can see, welding with aluminum isn't very difficult. With the SG 300 spool gun and an hour's worth of practice, you can begin building lightweight and corrosion-resistant aluminum accessories for your 4x4.