Hey Hawk,
Arc force helps add a little voltage to the arc when the electrode becomes close to or touches the work.
Generally.. High numbers on arc force are used for open roots; for example with 6010 and an open root the electrode goes right into the arc gap to form the keyhole.. If the electrode tends to snuff out, an increase in arc force will raise the working voltage for a short period and keep the arc ignited.
Usually the low-hi rods tend to produce more spatter than is tollerable with high dig settings... I normally run 0-3 when running E7018 unless I'm running extra low current for that rod diameter and am having sticking problems..
Anyhow.. Thats the nutshell version.... But if a higher number makes your low-hi work... There is not a thing wrong with doing what your doing.
By reddoggoose
Date 05-22-2009 15:24
Edited 05-22-2009 15:27
When welding SMAW with a Miller machine, the dig becomes active at about 19 volts. What this does is as the voltage drops or arc length decreases to below 19V, current will increase. This increase in current will act to clear the short (low voltage). Higher dig values are typically used on XX10 electrodes which are rods that typically have a "stiff" arc, especially when welding downhill on an open root joint, which will help push the bead into the root and minimize the rod sticking. When running a 7018, a lower dig value is usually preferred. This is because a 7018 typically transfers across the arc in a globular transfer. If those globs hang off the end of the rod and touch the plate voltage drops (short). The dig will increase to the needed amount to clear the short. Large short clearing currents will cause the short to clear, but will be at a high current which will cause large spatter (unloading). Low dig settings limit the amount of current available to clear the short, resulting in a cleaner separation of filler material and a softer arc. An easy test is to run a 1/8 7018 on a flat clean plate with dig set in Minimum. Repeat the test on another clearn plate with the dig set to Maximum. On the Max setting you will notice large spatter pop out of the puddle, this is the unloading from to much short clearing current. By knowing how dig works you can tell how well a particular machine will run a given rod by looking at the Volt/Amp curve for the machine, before you even pick up the stinger.