[martinr]

The voltage-current characteristic in a traditional stick DC welder has a drooping characteristic: as the arc length increases the current drops, and I gather that this is perfect for control of the puddle when welding out of position. Watching the display on my (TIG) inverter I see it really is constant current: no matter what the arc length is, the currrent is rock steady, so if I lenghten the arc the current does not change. I realise that the heat going into the puddle (Volts x Amps) should still fall as the arc is lengthened, but it won't fall as much as it would with a drooping characteristic, when the current would also fall.

So my question is: what new techniques (if any) does one need to learrn to be able to stick weld well in the vertical and overhead when using an inverter?

Thanks

Martin

[Otto Nobedder]

I've never noticed a difference, beyond the stability of the arc.

While the current remains the same, the arc length affects how concentrated the heat is, so you still have similar control. (My theory, anyway.)

Steve

[martinr]

Thanks, Steve.

Part of the reason I sought advice was this article http://www.millerwelds.com/resources/ar ... le108.html .

However, whilst the article intimates that Arc Force or Dig Control on the inverter alters the Voltage-Current characteristic, in practice on my inverter, arc force kicks in for a fraction of a second when the volts drops to something around 17V. It's difficult to be precise because the current boost lasts for an instant only, I guess till the voltage is above 17V and then it drops out. I can set arc force/dig control at anything up to 100% of normal current (i.e. double) but the only effect I can see is that it ensures the arc voltage doesn't go below about 17V, So I haven't seen that "it can create an arc that experienced operators describe as “soft and buttery” or “stiff and driving.” as the Miller article suggests.

Nevertheless, I am really pleased to learn that you haven't noticed any difference; that's quite reassuring. And many thanks for taking the time to tell me so.

Martin

[martinr]

For future reference for anyone looking for similar info, there's interesting stuff on pages 82 and 83 of

http://www.pronius.fi/uploads/Kayttoohj ... 00_ENG.pdf

implying a constant current curve is good for basic and rutile electrodes whereas a more constant-voltage curve is better for cellulose.

Martin