To also put in my two cents from what Howard said (which was awesome).
Purpose: To ensure process variables, variances, severity of occurrences, process validation, has been addressed and proofed. - to put in elementary terms.
Benefits: The same as purpose turned to a positive fashion. It ensures you can run a product at the best quality and delivery possible - to put in elementary terms again.
It will avoid rejections if you run an all automated system. There are still going to be variables you will not control. But if the severities are extreme you should take steps as a manufacturer to ensure you reduce the risk of failures to the point where you reduce those variables. And you have a corrective action process in place to try and prevent from happening again. This is all part of
APQP and PPAP themselves.
REJECTIONS from PPAP: Sounds to me as if the
DFMEA/
PFMEA portion(s) of PPAP wasn't put together quite well in the Pre Production/QPQP - PPAP process. If you are seeing rejects then Failure Modes and Severities weren't addressed at a multifunctional arena or completed sufficiently?
I have great knowledge of PPAP and APQP, so please feel free to e-mail me and I can give more info and tools/examples to use. It's been a couple of years since I've done the automotive world but it's like riding a bike. Do you have specifics you are dealing with that I may help you with?
On a personal level I LOVE PPAP and APQP, it makes sense to me. I would use it more here if we weren't a job shop.