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tig electrical requirements?

I want to make a homebrew tig from a stick welder I picked up very cheap. I have no experience of welding, although I can solder and braze. I know electronics, I can probably produce any current and voltage and impedence and waveform within reason, but I don't know what is required for tig welding.

This is what I've read, any comments will be much appreciated:

The open circuit voltage is not very important when an arc stabiliser is used. Are there occasions when you might want not to use a stabiliser, and what should the open circuit voltage be then?

I will only be welding thin sections - some very thin - in stainless and aluminium, so I probably won't need many amps, perhaps 80 max. In mig welding short bursts of high current with long gaps in between are used for better deposition without overheating, I assume that is not used in tig welding.

The main control should be of the current. A non-saturating inductor in series with the output is useful - any suggestions as to value?

The welder should provide AC and DC, and a hf arc stabiliser (I've read 20 kHz, 2kV, 2 ma is about right for an arc stabiliser).

I have heard about using square waves, what is the advantage of that? Is balancing the positive and negative portions of the waveform really necessary or useful?

A linked question is how useful is it to be able to vary the frequency of the ac waveform? If I only had the options of DC or AC at fixed 50-50 cycle

50 Hz, how much would that limit what I can do?

Is there anything else I haven't mentioned?

Thanks,

Reply to
Peter Fairbrother
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If your stick welder has DC output you can do scratch-start TIG without the HF or arc stabiliser. I don't think you can do that with AC though and you'll want AC to TIG aluminum.

Maybe this will help:

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Best Regards, Keith Marshall snipped-for-privacy@progressivelogic.com

"Even if you are on the right track, you'll get run over if you just sit there." - Will Rogers (1879-1935).

Reply to
Keith Marshall

It doesn't have DC - it's a very cheap welder, cost me £8 with a bunch of goodies - but that can be fixed quite easily.

What's the difference between HF and an arc stabiliser? I was planning to superimpose a 2 kV pulse on the electrodes at 20kHz, to do both jobs (striking and maintenance). Would that be okay?

Reply to
Peter Fairbrother

If it's got DC+, then it has DC-. Just use the opposite welding lead as your stinger. Surely you knew that and you're just goofing on us, right?

JTMcC.

cost me £8 with a bunch of

Reply to
JTMcC

I'm not sure but I believe the "-" he used was for a pause rather than for "minus", much like a comma or semicolon.

Best Regards, Keith Marshall snipped-for-privacy@progressivelogic.com

"Even if you are on the right track, you'll get run over if you just sit there." - Will Rogers (1879-1935).

Reply to
Keith Marshall

Probably nothing but I haven't look into it well enough to know for sure. I worked on a Miller Econtig once and it had a high voltage pulse rather than the typical high frequency circuit and worked just fine. It generated a pulse and fed it to a HV transformer that was then coupled to the main welding connection through a capacitor. In the unit I worked on the cap had apparently shorted and the full welding current hit the HV transformer. For some strange reason this let the magic smoke out of the transformer and it didn't work any more. :-D

When I replaced the transformer and cap I also placed a .5amp fuse between the 2 so that if the cap shorts again it'll hopefully blow the fuse rather than the $110 transformer.

Reply to
Keith Marshall

I'm sure you're right, just goes to show how my mind works!

JTMcC.

Reply to
JTMcC

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