On Sat, 26 Nov 2005 17:55:02 GMT, Ignoramus12834
wrote:

On Sat, 26 Nov 2005 16:47:25 GMT, Jim L. wrote:
Congrat's.

Thanks. I may try to weld aluminum this weekend.

I'm wondering if you came across any schematics of commercial tig
inverters during your hunt? Or are they drawn as black boxes? Thanks, Jim.

I have not found anything.

The only thing that my inverter does not have, is control of power
when electrode is negative, and separate control when electrode is
positive (I think that it is called AC balance). For my inverter, the
absolute value of the voltageand current is the same for positive vs
negative half cycle.

They control balance with duty cycle control, which you can also do.
Start with 50-50, or maybe 60% SP (electrode negative) and 40% RP
(electrode positive). Practice with that until you can make
consistently good welds. With only 200 amps max current you'll be
limited to fairly thin aluminum, maybe 1/4" max. I'd suggest
starting with 1/8" material. Don't blame the machine if you don't
achieve instant success. A lot of excellent aluminum TIG welding
is done with straight AC machines. When you can lay a stack of dimes
in aluminum, then you can start tweaking the dutycycle or AC balance
to optimize penetration with just enough RP cleaning to do the job.

I've followed this saga with some interest, will be interested in your
results. I've thought about doing something like that for years,
but have never been motivated to do it because I've been satisfied
with the results I get with straight AC.