Weld Examination
The Weld Examination domain covers how a robotic weld is inspected, by which method, at which stage, and against what acceptance criteria. Items mix method selection with the paperwork around it: who may inspect, what gets recorded, and what turns a discontinuity into a rejectable defect.
Methods and where they work
- Visual testing is first, always, and covers the most ground: bead profile, undercut, spatter, overlap, crater, arc strikes, weld size, and fit-up.
- Penetrant testing finds surface-breaking defects on nonmagnetic material such as austenitic stainless and aluminum.
- Magnetic particle testing finds surface and near-surface defects in ferromagnetic steel but is useless on austenitic stainless.
- Ultrasonic testing finds planar and volumetric defects through thickness and is effective on lack of fusion; it needs a trained technician and a written technique.
- Radiographic testing images volumetric defects well but is weak on tight lack-of-fusion planes aligned with the beam.
Stages
- Before: joint preparation, fit-up, gap, consumable identity, WPS availability, preheat equipment.
- During: current, voltage, wire feed speed, travel speed, preheat and interpass temperature, gas flow, CTWD.
- After: final visual, then required NDT, dimensional check, and documentation.
Gauges
Fillet gauges measure leg length, the undersize gauge measures undercut depth, the Hi-Lo gauge measures internal misalignment, and a V-WAC gauge measures undercut and crown. Read each leg of a fillet separately; a convex bead can look large and still be undersized in leg.
Worked example
A drawing calls for a 5/16 in fillet. The gauge shows the vertical leg at 5/16 in and the horizontal leg at 1/4 in, with a slightly convex face. The specified size is leg length and must be met on both members for a symmetrical fillet. The 1/4 in leg is 1/16 in undersize, outside the allowance most structural criteria give without engineering evaluation, so the weld is reported and the cause traced to work angle and torch angle rather than wire feed speed. Repair is planned against the code provision, not the inspector's opinion.