Arc-process evidence

CO2/MIG Voltage-Current Setting and Spatter Diagnosis

Use this page when a MIG/CO2 welder has unstable arc, spatter, stubbing, burn-back or a mismatch between voltage and wire-feed current.

Voltage and current must be diagnosed together

In CO2 short-circuit transfer, panel current is mainly wire-feed speed. Voltage controls arc length and melting behavior. A narrow voltage mismatch can turn a stable arc into harsh popping, burn-back, wire stubbing or spatter.

Redrawn voltage-current matching map: too low, matched and too high voltage zones.

Setting symptoms

Observed behavior	Likely direction	Evidence to check
Wire stubs into puddle / harsh shorting	Voltage too low or wire feed too high	Raise voltage slightly, check wire speed, contact tip and liner drag.
Long arc, irregular popping, heavy spatter	Voltage too high for wire-feed current	Reduce voltage, verify stickout and gas flow.
Arc unstable after cable extension	Voltage drop / feedback issue	Check return cable, voltage feedback lead and output cable length.
Porosity with unstable arc	Gas shielding and surface condition	Gas purity, nozzle blockage, flow rate, rust/oil/water and wind.

Rules of thumb

For short-circuit transfer below roughly 200 A, use U ≈ 0.04I + 16 ± 2 as a starting zone. For higher-current spray-like regions, use U ≈ 0.04I + 20 ± 2 as a separate starting zone. These are diagnostic anchors, not final procedure settings.