Aluminum Workshop: Sizing up processes, power source capabilities for aluminum welding

Q: I have a small shop at my home and would like to add a piece of welding equipment to increase my capabilities to weld aluminum. But, I’m confused. I don’t know whether to buy a gas tungsten arc welding (GTAW) machine or a gas metal arc welding (GMAW) machine. Any suggestions?

A: In general, you get what you pay for, so don’t expect that a $500 power supply will be able to do the same things as a $5,000 power supply. So now let’s look at your options:

• GMAW power supplies that fall within the $100 to $300 range usually come set up for flux-cored arc welding (FCAW) of mild steel. They don’t typically have a gas solenoid or other things needed to perform GMAW. Sometimes these parts are available as a kit from the manufacturer, but in general these units are not really suitable for aluminum GMAW.
• GMAW powers supplies that fall within the $400 to $750 range are available in either 110-V or 220-V input, so be aware of which voltage the machine runs from. These units can do a good job on relatively thin aluminum—up to thicknesses of 3/16 in. Often the manufacturer has an aluminum feeding kit available that will include drive rolls and a gun liner to make your job easier. A few manufacturers have models that will let you plug in a separate spool gun to feed aluminum filler wire. This is something you should definitely consider even though it would add $200 to $300 to your investment.
• Lower-end industrial GMAW power supplies that fall within the $1,000- $1,500 range usually have a capacity of 200 to 250 amps, can weld material up to around ½ in. thick, and include a gun. Contrary to what you may think, it is better to use a 10-ft. gun rather than a 15-ft. gun because a shorter cable results in fewer wire feeding problems. Use a 3/64-in.-dia. wire for the same reason. In my opinion, these machines are the minimum you should have if you plan to make a living from welding aluminum. You’ll find that some of these are three-phase units, so be careful.
• AC GTAW power supplies usually cost approximately $2,000 and have a capacity of around 200 amps. They do an excellent job of welding aluminum in thicknesses of up to ½ in. Just be sure to purchase a unit that has both AC and DC outputs. Cheaper units are available, but they accommodate only DC welding, which will not help you in welding aluminum. GTAW units are better suited to weld very thin aluminum than are the GMAW units discussed here.
• Pulsed GMAW power supplies typically cost $5,000 to $10,000 and can weld aluminum of all thicknesses, especially when paired with a push/pull gun. Obviously, they are quite a bit more expensive than the other options. If you do a lot of industrial aluminum welding, these are your best choice.

Good luck!