Flexible robotic cell for in-process inspection of multi-pass welds

Welds are currently only inspected after all the passes are complete, and after allowing sufficient time for any hydrogen cracking to develop, typically over several days. Any defects introduced between passes are therefore unreported until fully buried, greatly complicating re-work and also delaying early corrections to the weld process parameters. In-process inspection can provide early intervention but involves many challenges, including operation at high temperatures with significant gradients affecting acoustic velocities and hence beam directions. Reflections from the incomplete parts of the weld would also be flagged as lack of fusion defects, requiring the region of interest to adapt as the weld is built up. The collaborative SIMPLE (Single Manufacturing Platform Environment) project addresses these challenges by incorporating robotic inspection within a robotic TIG welding cell. This has been accomplished, initially with commercial off-the-shelf ultrasonic phased arrays, but flexibly enough to adapt to future developments with higher temperature solutions. The welding and inspection robots operate autonomously. The former can introduce deliberate defects to validate the the latter which uses 5MHz 64 element phased arrays on high temperature wedges to generate sector scans after each weld pass. Results are presented, confirming the challenges have been addressed and demonstrating the feasibility of this approach.