[martinr]

Nice!

I'd have to dig out my old physics books to find out what the effective resistance would be of an ionised path through argon. Could well be low enough that the actual effect on any 'normal' welding distance variation is in effect pretty much 0.

Quite interesting though as many docs and videos mention the arc effectively getting 'hotter' (and of course more diffuse) when long-arcing, while it seems the effect is more about the diffusing and putting the heat in a much bigger cross-section on the work piece than when keeping a short arc making it seem like it's hotter. It seems it's just getting less focused.

MMA/stick should be pretty similar as it's (supposed to be ) constant-current as well, but a good comparison to plain TIG.

MIG and such should be a lot more dynamic/spiky voltage and current wise, but that's of course also part of the process esp. when using short-circuit. May well be that the spray-tranfer types here make for a much more smooth/consistent power delivery similar to TIG once it gets going.

Bye, Arno.

Hi Arno,

I had a look at how voltage and current vary on the Manual Metal Arc (stick) process.

I turned off arc force and hot start and used a 6013 rod.

Here, I start with a tight arc and then part way through I make a longer arc. This was at 125A.

On this run, there is a negative slope to the characteristic: 121A at 21.8V, and 104A at 35.6V. That would give a slope of -40 degrees.

Volts vs arc lenth 1.jpg (77.04 KiB) Viewed 1962 times

Here I start with a tight arc and then alternate between a tight arc and a longer arc. The current was lower at around 94A. At 20.0V I have 93.8A, and at 31.5V I have 91.6A. That gives a slope of about -80 degrees. Almost like falling off a cliff.

Volts vs arc lenth 2.jpg (156.67 KiB) Viewed 1962 times

I follow Jody's rule anyway: set the current so that the rod does not stick on a tight arc, and then keep a tight arc!

So there’s 2 points on the V-A characteristic curve with the tangent at those points. Clearly, I could take measurements at more (different) current settings, between, say, 70A and 140A and construct a much more detailed characteristic curve.