Troubleshooting guide › Process troubleshooting › Drawn-arc stud welding problems
In drawn-arc stud welding the gun lifts the stud, an arc of up to 2000 A melts the stud end and the plate for up to a second or more, and the gun plunges the stud into the pool while a ceramic ferrule shapes the collar. Every one of those steps leaves evidence in the collar, so the collar is the first thing to read. This page covers M10-M22 studs and shear connectors on structural steel, including through-deck welding on composite floors.
Reviewed by the Cruxweld technical team, October 2026. Settings are starting points to confirm on a test piece; acceptance is decided by the code or drawing the job is built to. Checks marked “call” are for our technical team.
| Collar | Meaning | Change |
|---|---|---|
| Even, bright, complete all round, slightly flattened | Correct | Nothing |
| Collar missing on one side | Arc blow pulling the arc to one side; gun tilted; ferrule not seated flat; wet or dirty plate on that side | Move the earth or use two earths; hold the gun square; seat the ferrule; clean |
| Collar small, dull, incomplete | Not enough heat: current or time too low, lift too small, plate cold or scaled | Raise current or time; set lift (3 mm reference for 16-22 mm studs); clean the plate |
| Collar large, splashy, undercut into the plate | Too much heat: current or time too high, plunge too late or too slow | Reduce current or time; check the gun plunge is immediate on release |
| Collar on one side only with the stud leaning | Stud not concentric with ferrule and chuck; support plate loose | Re-align stud, ferrule and collet; lock the support plate screw |
| Stud height varies from stud to stud | Extension set wrong; chuck wear; studs of mixed length; plunge inconsistent (dry gun shaft) | Set extension from the display scale rule; replace a worn chuck; one stud batch; lubricate the gun front shaft |
| Porous, honeycombed collar | Wet ferrule, damp or rusty plate, oil, paint | Dry ferrules (keep them sealed; bake damp ones as the ferrule maker specifies); clean the plate |
Tests: bend each test stud past 15 degrees with a bending wrench and back to zero; it passes if it does not break. Torque test with a nut and torque wrench to the values for the stud size (for example about 2.1 kg-m for a 10 mm stud, 11 kg-m for 16 mm, 21 kg-m for 20 mm on Cruxweld CDS-2500 procedures). Do trial welds before production and again whenever studs, ferrules or the gun set-up change.
Insufficient fusion: current or time too low, lift too small, plunge too slow, dirty or scaled plate, wet ferrule.
The lift sets the arc length: too small gives a short, hot, unstable arc and a small collar; too large gives a long arc that blows out and a dull collar.
The stud must plunge the moment the trigger is released; a sticky or dry gun shaft, a weak spring or a long cable delay gives a cold plunge and a weak joint.
Ferrule for the wrong stud size, cracked, wet, or not seated flat on the plate; the collar then escapes or is porous.
Deck galvanising, water or dirt trapped between deck and beam, gap between deck and beam, deck too thick for the stud, current too low for the extra layer.
Collar missing on one side near edges, beam ends and clamps.
The pool sags; 16 mm and larger studs are not recommended vertical.
Stud-to-plate ratio too high: above 4:1 on plate over 3 mm, or above 3:1 on 1.5-3 mm plate.
Over-temperature: duty cycle exceeded.
A supply phase lost, under-voltage or phase unbalance.
Stud and plate short-circuited: the gun did not lift, or the stud is welded to the plate from the previous attempt.
Normal: the output switches off without load after about 10 seconds.
You read the collar on every stud and you bend-test a sample: one at the shift start and after any change, more on inspected work. A full, even, bright collar on a square stud is the sign; anything else is a setting or set-up change waiting to happen.
Yes within the procedure: deck held tight to the beam, dry, current and time raised for through-deck, and the first studs on every beam tested. Standing water or a gap under the deck fails studs faster than any setting.
The machine must hold the set current for the full weld time at the duty cycle of the job (shear connectors at 1500-2000 A, one every few seconds, is heavy work) and give repeatable lift and plunge through the gun. The fault codes and panel timers on the CDS-2500 make the settings repeatable from shift to shift; the gun set-up is what the operator controls.
Send a photo of the weld or cut, your machine model, consumable and plate thickness. Our technical team replies on WhatsApp with the likely causes and the next checks to make.
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