MB Sims, our company, and others on this site are audited by another organisation, and one thing they ask for it proof that at least yearly our welding machines are "calibrated" once a year for structural shops per D1.1, and quarterly for Bridge shops.
I spoke with my Nelweld rep. and I would have to send the units to Ohio to have them calibrated, and its around $750 not including shipping. I don't think other companies have done this, I can't see other places shutting down that portion of their facility for this.
We do do the pre-production tests, and I would agree that its usually operator error. I get nervous around audit time regarding the stud welder, so now I have time to address the issue, but I can't have the shops shut down and send the units out.
The Nelweld rep said to calibrate them to NIST with paperwork is very involved due to the circuitry inside the units.
Chris