ISO 9001 certification (which must be renewed periodically) assures that the firm has the procedures in place to deal with problems. Although those procedures also help to prevent problems, they can not guarantee that problems will not come up. Certification checks that the procedures are followed, but when away from the intense period around certification, it is hard to guarantee how well the procedures are followed. Some firms do very well, some not so well. Those that constantly adhere to the 9001 standard usually have exceptionally well run organizations, although they may be overly bureaucratic.
Yep. As a former QA inspector trained in ISO 9000/9001 I can state that getting people to adhere to it can be damned difficult if they don't want to. I regularly had loud arguments with one plant manager who said I wasn't a team player, and to whom I countered he wasn't my team captain. I received so much harassment and even verbal threats from his underlings that I took to cataloging them and reporting them to HR every time they happened, including the exact language used. HR knew if anyone tried to get me canned the company would have some real problems, so they tried to get people to shut up, with only some success.
In another place I worked I was physically assaulted by the shop manager. It just happened to be that one of his own machine operators had asked me to look at some parts, which I was doing when he became irate and threw me out of his shop, so his sense of timing was particularly bad. He got severely reamed by the CEO and transferred to a department where he was no longer in charge of anything- an outcome I was satisfied with.
Both places were fully certified, but in both there had been a history of intimidation and marginalizing the QA departments- something certification didn't change. What was different in me from most other inspectors was I had worked as a machinist long before I became an inspector, so the machine shop couldn't browbeat me or pull the wool over my eyes the way they could with others. I was their equal, and knew it. So they figured by making me miserable I'd quit. What it did do was increase my resolve to hold the line, and cause me to always keep my ass covered. I left the first place for a better job, the second went out of business and we all lost our jobs. But I left those places knowing I upheld the certification as I was required to by our ISO manual, which many inspectors didn't.
Sorry to say, ISO 9000/9001 is often in practice more like a statement of intent, than a binding document. It's supposed to be binding, in that if it's specified in manufacturing contracts it's part of the contract and must be followed; but the attitude far too often toward QA is "Who's gonna tell, if you don't?"
Bottom line, it's the sincerity and resolve of the people in charge that determines if the ISO certification means anything or not.