There are lots of equipment options and you may already have most of what you need.
By Tom Jackson
While steel is what most contractors need to weld most of the time, there is the occasional aluminum machine component, architectural feature or fabrication that requires aluminum welding. The best way to weld aluminum is with a TIG (tungsten inert gas) machine using AC current and 100-percent argon shielding gas. But that doesn’t mean that’s the only set up you can use, nor does it necessarily mean you have to go out and buy an entirely new welding machine to work with aluminum.
For a quick fix there are spool gun adaptors and high frequency AC generators that retrofit to certain MIG and stick machines. You can also get separate AC/DC stick/TIG welders and inverters that can be plugged into engine driven machines with auxiliary power or into a 115-volt or 230-volt power outlet in a building or shop. And if you want to go for the whole shebang there are “multi-process” welding machines that do all three: stick/MIG and TIG as well as plasma arc gouging.
Here’s the look at these options, starting with the most typical situation, that of a contractor who already has an engine driven MIG or MIG/stick DC welding machine.
Spool and push-pull guns
Aluminum wire is softer than steel and is difficult to feed through a standard MIG gun, so you need a specialized wire gun, either a spool gun or a push-pull gun. These can be fitted to a variety of engine driven welders, and today’s regulators can work with a variety of gasses so you don’t need a different regulator to handle argon gas.
A spool gun helps eliminate bird nesting (the tendancy for thin wire shavings to accumulate) by putting a one pound wire spool on the gun that feeds only a few inches. They allow the operator to use longer cables, generally 15 to 50 feet, but may limit access in tight spaces.
A push-pull gun has a motor in the gun that pulls the wire through the liner while a motor on the welding machine or feeder control assists. This push-pull action maintains constant tension on the wire to help eliminate birdnesting. Push-pull guns are lighter and more ergonomic and the spools don’t need to be changed out as often. They also let you use cables up to 50 feet long. Push-pull guns are more expensive, but offer increased productivity.
John Leisner, product manager at Miller Electric, recommends buying a bigger engine drive if you intend to weld aluminum with one. “The base purchase price is more expensive than a smaller engine drive, but the adaptor required to operate the spool gun on the smaller machine is considerably more expensive,” he says. As an example, he says you could get a Miller Trailblazer 275 or 302 with a full aluminum set up for roughly $200 to $400 less than a Bobcat 250 with the same set up. And the higher amperage machines allow you to run auxiliary tools at the same time without causing a lag in weld or generator quality, he says.
One advantage of using a stick/MIG machine with DC current to weld aluminum is that it’s fast, says Jim Harris, senior product manager for TIG equipment at Lincoln Electric. What you sacrifice is precision and appearance. And in most cases it’s hard to MIG weld thin aluminum – nothing below 1/16-inch-thick material, 1/8-inch at best. Aluminum conducts heat much more rapidly than steel so it’s easy to burn through material. One solution to this problem is a process called pulse welding, which alternates between a peak high current and a low background current. The peak high current gives you a “spray” effect that fills the weld puddle with thousands of tiny droplets for structural integrity while the background current helps control temperature. Pulse welding technology was introduced within the last decade.
Tapping into TIG
TIG welding is the pro’s choice when it comes to precision welding, good appearances and non-ferrous materials such as aluminum. It’s too slow for production applications like hardfacing, pipe welding and boom and bucket repair. But TIG welding is growing in popularity thanks to a number of automotive and motorcycle how-to shows on television. TIG welding also has a prestige value. If you’re looking to get your guys pumped up about their skills and professionalism, a dedicated TIG welder might be just the ticket.
Aluminum TIG requires gas shielding just like MIG (only 100-percent argon), a specialized tungsten-tipped torch, AC current and a foot pedal to vary the heat and current. The tungsten tips of TIG torches get very hot. Some use air cooling but TIG welding above 200 amps typically requires a water-cooled torch.
There are several set ups that can get you into TIG welding. These include:
High Frequency AC Generators. If you already have an engine drive welder, it may be configured to accept a high frequency AC generator. This is an add-on accessory, not a separate welding machine that gets 120-volt AC power from the engine drive, says Eric Snyder, senior product manager for engine driven welders at Lincoln Electric. A high-frequency AC generator turns a stick machine into a TIG machine by adding high frequency and a gas solenoid which are needed for AC TIG welding. To find out if your engine drive is compatible look for a control cable connector that will accommodate a foot pedal or a hand-adjustable current control unit designed for TIG welding.
Inverters. You can also buy a dedicated TIG inverter welder that plugs into the auxiliary power outlet on your engine drive welder (if you have one), or into a wall socket. Most of these offer DC and AC welding current, so you can do both stick and TIG welding. While more expensive than stationary TIG welders, the inverter TIG welders, at around 40 to 50 pounds, are smaller and more portable and draw fewer amps than the stationary TIG welders. Inverters allow contractors to grow into advanced TIG capabilities such as pulsed TIG and advanced arc tuning, while also offering stick welding capabilities they are already familiar with, says Harris.
“You have some very advanced controls to adjust the output frequency of the machine and narrow or broaden the arc,” Harris says. “If you go up in AC output frequency it will focus the arc tighter. Turn it down and it will broaden it out.” And TIG machines can also give you pulse welding for heat control on thin material and no spatter, he says.
Inverters from 200 to 300 amps will give you the capacity to weld aluminum up to about 1⁄4 to 1⁄2-inch thick respectively. Beyond that and for more production level TIG welding you may want to look into one of the heavier stationary TIG models.
If you’re in the market for a new welding machine these are units that will do all three processes: stick, TIG and MIG. The most versatile machines will give you DC stick and MIG welding and AC TIG welding plus auxiliary power. EW