Set-up, Adjustment and Troubleshooting of FCAW Equipment and Parameters
This domain tests the relationship between the machine settings and the arc, and your ability to diagnose a symptom back to a cause. It rewards knowing which knob does what.
Set-up essentials
Confirm polarity from the WPS: gas-shielded FCAW normally runs DCEP (electrode positive), while most self-shielded wires run DCEN - check the data sheet, because reversed polarity on a self-shielded wire gives a harsh, spattery arc. Gas: 100% CO2 at roughly 15–20 CFH, or Ar/CO2 75/25 at 20–25 CFH. Wire 1.2–1.6 mm; stickout 10–19 mm (3/8–3/4 in).
What each setting does
Wire feed speed sets current and deposition rate. Voltage sets arc length and bead width. Travel speed sets bead size, penetration and heat input. Slope and inductance trim arc stiffness and spatter.
Symptom-to-cause map
Stubbing or the wire stabbing the plate: voltage too low for the WFS. Long arc, heavy spatter, undercut: voltage too high. Birdnesting: drive roll tension, worn liner, kink, or burnback at the tip. Porosity: gas flow, leaks, draughts, damp flux, dirty plate.
Worked example
A welder raises WFS from 220 to 300 ipm and the arc immediately starts stubbing. Reasoning: higher WFS raises current and feed rate, so the wire arrives faster than the arc can melt it and arc length collapses. Correct response is to raise voltage (roughly 1–2 V per significant WFS step), re-check stickout, then confirm the settings remain inside the WPS range before welding production joints.
Traps that cost marks
Setting by sound alone without checking the WPS window. Reversing polarity on a self-shielded wire. Reading gas flow at the regulator instead of the flowmeter at the torch. Fixing birdnesting by over-tightening the drive rolls, which crushes the wire.