Dave, square wave machines have a couple of very useful features not available with ordinary sine wave machines. I don't have experience with the smaller range of welding products but I can comment on our Miller Syncrowave 250.
Probably the most important factor is the ability to adjust the AC balance on the machine so that either more positive or negative side of the cycle can be introduced depending on whether your after more or less penetration. Another benefit is the ability to introduce ramp up or ramp down and to use crater fill. These don't apply if your using a foot or handpiece current control.
Also pulse control can be had as an option.
The next step which we have gone is with our new OTC machine which is a pulsed hybrid wave inverter. This is similar to Miller's top of the range Aerowave and allows adustable hertz control, even greater AC balance control and in hybrid wave the ability to introduce DC wave into the AC wave for even greater flexibility.
The aerowave and our OTC machine are both very much top of range Tig machines.
If you can afford to go square wave, I'll guarantee you won't be disappointed.
Regards Andrew.

There is no need for high frequency arc stabilization since there is essentially no time in the cycle in which there is reduced current flow.

I have only used this type of equipment one time and it was great. There didn't seem to be any problem with getting shocked when dipping the wire into the puddle either. (I imagine because there was no high frequency).


Have a nice day

G Austin

Dave to answer your question first most directly. NO Square wave technology is not a requirement to make good quality welds in aluminum alloys with AC Tig.

Having said that, my advice would be to spend the extra money to get it anyhow. As I explain what *Square Wave* is I think you will come to understand why.

Squarewave is the AC output of a power source that has the ability to rapidly switch between the positive and negative half cycles of alternating current. This is accomplished with advanced circuitry. Where the normal AC sine wave is smooth, the sharp corners of the square wave represent the quickness of the change between polarities and can also be used to represent balance control (dwell time on each side of the half cycle). Greater amounts of EN create a deeper, narrower weld bead and better joint penetration. Greater EP values remove more oxide and create a shallower, wider bead. Transformer-rectifier GTAW machines can adjust EN values from 45 to 68 percent.
The faster and sharper the machine can switch between polarities the greater the chance is that the AC arc will remain smooth. When an arc breaks between the half cycles and does not reinitiate (this is called rectification) the welder experiences popping and lack of smoothness in the arc and reduced quality in the welds.

The Square Wave power source will help to eliminate rectification and provide balance control which is often needed when welding a variety of aluminum or magnesium alloys. If you're looking at high production, heavy castings or a large variety of different aluminum components the square wave machine will offer flexibility the lesser machines just don't have. There are some jobs that a square wave power source with balance control can do that lesser machines just cant.


Every square wave Tig power source machine (with the exception of the most expensive models) come with an option (switch) to use superimposed high frequency. Let me be very clear on the following point. With basic square wave welding power sources superimposed high freq. is required! The machines mentioned in the above post (Miller Aerowave and the OTC) are exceptions and are most easily envisioned as machines with two separate power sources (one DCEP and one DCEN) and a computer that controls them and switches them back and forth at variable amperage and frequency. We are NOT talking about these unless you have about $9,000 bucks to just get started.
Besides, with a normal welder it won't take you long to discover the working benefits of Continuous High freq. once you try to work without it.