Converting MIG to TIG

[Rotate]

Is this possible? I except for the high frequency starter, everything else should be same. Lincoln Electric touts square wave technology. Is this significantly better than sine wave AC?

Albert

[halfnut]

Big problem here. Mig machines are constant voltage machines, Tig and stick machines are constant current. I have noticed some of the new portable gas powered rigs have a switch to go from one mode to the other.

Also have to have a way of hooking up that throttle peddle.

Vrooom.

[KACHINKOO]

ROTATE
I HAVE A LINCON 300 AMP SQUARE WAVE 5 YEARS OLD THAT HAS NEVER EVEN HAD A HICCUP. IT IS A TIG.NEVER TRIED WHAT YOU WANT BUT BEEN TOLD IT SHOULDN'T BE DONE BECAUSE OF THE CONSTANT AMP-CURRENT CONFLICT. IT WILL WORK BUT NOT THE BEST IN ONE MODE. I WOULD RATHER HAVE A SECONDARY MACHINE THAT WAS MADE FOR THAT PURPOSE INSTED OF ONE THAT DID BOTH POORLY! MOST OF MY WELDING IS TIG, I HAVE RENTED A MIG ONLY ONCE IN THE PAST 8 YEARS AND IT SHAVED ABOUT 60 HOURS OFF A PROJECTS TIME. WORTH THE RENTAL, NOT THE SALE PRICE FOR ME. DAVE

[Rob Frink]

Rotate,

My first Tig was an old westinghouse 300A Machine from 1964. There was no technology in that machine. It had a bank of resistors and breakers for "rough" current selection and a huge rheostate with a servo motor for "fine" current adjustment. It was about the size and weight of a Bank Vault!

It welded great! But was replaced for a smaller more compact machine to save space and to take advantage of "technology".

I got one of the new ESAB Multimaster 260's. Combination Mig/Tig/stick...with "state of the art" arc stabilization, CCW, CVV...blaa blaa blaa. It is smaller and more compact, the arc is smoother and the "soft" start circuitry is cool.....but, it is not noticably better than the old dinasour that it replaced.

Since my new state of the art machine will both MIG and TIG from the same power source....I say, sure! your Lincoln would probably TIG nicely once you got the High Freq arc-start worked out. If you TIG with AC, then you need a constant HI freq to keep the arc while the current changes direction......for DC TIG, you just need to get the arc established then you can shut off the hi freq.

Maybe drop the guys at lincoln a note....see what they say.

Have fun with it and be safe.
Rob

[Rotate]

Does anyone know how the HF of TIG work? It is just high frequency or is it also high voltage? I would think you need the high voltage to start the arc (or sustain it for AC), so why the HF? How do you avoid the high voltage source from getting shortened by the low impedance of the secondary winding ofthe transformer? Is there an inductor which keeps the HF out of the power supply circuit?

As you can see, I'm guessing at how all this works.

Albert

[Thrud]

Albert
Older machines used spark gaps but rf interference and voltage spikes are bad back out the utility line. Newer units are using Power MOSFET switchers to generate square wave AC and reverse/straight polarity for GTAW/GMAW/stick as well as gas plasma cutting torch. I think the best units on the market are the Millers but I am biased in that those are the machines I have used most.

[This message has been edited by Thrud (edited 04-14-2002).]

[JCHannum]

I've done lots of TIG welding with a DC welder and TIG torch. Mild and stainless steel both. Scratch start. You don't need Hi-freq unless you get into aluminum.

Lincoln makes a nice combo unit too. It was around $1500 last time I looked.