Why your GMAW machine has no amps knob
The machine
Three things control this arc. Two are knobs. The third is your hand. Move the sliders and watch what the amps do, because there is no amps knob on a GMAW set.
A CV power source holds terminal voltage nearly constant (curve slope around 2 to 3 V per 100 A). The welder presets voltage and wire feed speed. Current is an outcome: it settles wherever burn-off rate equals wire feed speed. Electrode extension is the hidden third input, set by the hand.
(current)
The event you just watched takes milliseconds on the real machine, faster than your eye. That is why the arc never looks like it is hunting. No verified published figure exists for the exact recovery time; it varies with current and wire.
For lecturers and industry trainers
This interactive dashboard is built to help you explain to boilermakers, apprentices and other welders how a constant-voltage GMAW machine really behaves. Work the controls in front of the class to show:
- the effect of wire feed speed, which sets the welding current;
- the effect of voltage, which sets the arc length;
- the effect of stick-out, which raises the electrode resistance and drops the current, so small changes in stick-out give the welder fine control over amperage without touching a dial;
- and how the shielding gas has a significant influence on the threshold current between dip, globular and spray transfer.