Is it one of the switch selections?
Two possibilities are that it is a setting to use when deep penetration
is wanted, such as butting two thick plates together, or that it is
meant to be used with a gouging torch for grooving out or removing
Just a wild assed guess though.
From the Miller welder website.
"Offering exceptional arc characteristics for different electrodes and
joint designs, the Trailblazer 302 Diesel features four preset DIG
settings. Providing combined DIG and Process switch, along with preset
DIG settings, offers simple set up without the complication of multiple
switches. The four preset DIG settings include: soft arc and smooth 7018
performance, medium-soft driving arc, medium-stiff driving arc and
driving arc such as pipe welding."
About the Miller Maxtar 200.
"DIG control allows the arc characteristics to be changed for specific
applications and electrodes. Lower the DIG setting for smooth running
electrodes like 7018 and increase the DIG setting for stiffer, more
penetrating electrodes like 6010."
Miller Inverter power sources
"Dig control for Stick welding. Dig control prevents the electrode from
sticking when the arc gets too short. This is helpful for an open-root
pass or tight fit-up work and aids in arc initiation."
I am not sure electrically what is changed when you change the DIG
setting, but you can see above examples of how the DIG control is
supposed to affect the welding arc, apparently by affecting the
penetration and tendency to stick. I have heard of this before. As far
as I know it affects stick welding only, but I could be mistaken.
Arc welding is nominally done with a constant current supply. DIG
alters this by increasing current at lower arc voltages resulting
from shorter arcs. This keeps rods from sticking, among other
The power to the arc is arc current * arc voltage, so as the arc get
shorter and voltage drops, power (hence heat) goes down unless
current is increased.
Arc Force - Also called Dig and Arc Control. Gives a power source
variable additional amperage during low voltage (short arc length)
conditions while welding. Helps avoid "sticking" stick electrodes when
a short arc length is used.
I always thought the 'arc force' control squared off the edges of the
sine wave to give a better 'punch through' voltage. Suppose I'll have to
put a 'scope on the output of the stick welder and have a look!
As for what it does for you, increasing the 'arc force' sure helps on
rusty or dirty material. Increases the spatter tho.
Roy, I received some helpful answers here and tried to dig some
information myself. Here's a little summary.
The story, I think, is as follows: (as Don said) on CC welders, when
the electrode is very close to or shorts to work piece, the voltage in
the arc drops dramatically and the current at that voltage does not
produce much power (power = voltage * current).
Because of low power, there is not enough heat and electrodes stick to
workpieces. Very annoying, as it messes with fitup, finish and is
To correct it, good welding machines have a "DIG" or "ARC FORCE"
adjustment, that increases current when the welder detects a short arc
or short circuit condition by seeing low circuit voltage. That instant
current increase increases power in the arc, and that instantly "digs"
a little hole in work by melting it (and melts more electrode) so that
a longer arc is maintained.
That prevents electrode sticking and can help increase penetration.
We have a big AC/DC stick welder sitting in the corner, fairly new,
rarely gets used anymore. I doubt it has much of any electronics inside,
I need to have a look at how it does the adjustment. Shop manager will
have a hissy about taking the case apart but you have my curiosity working.