Re-PPAP after updating CMM program?

I am relatively new at the company I work for. In going through cmm programs, I have found an overwhelming majority of them have serious flaws, to the point that they are simply wrong, and could not be considered correct by any interpretation. The prior persons programming did not understand programming, GD&T, or even blueprints to a great degree.

This company spends hours and hours writing up deviations. I'm taking a guess that at least 70% of these could be resolved by reprogramming. I don't think the parts are the problem, but rather the programs. I continue to be told "we made them like this for the PPAP, and they were accepted, so we have to make them the same way again, or else we have to PPAP again".

I never had the understanding that changing the program requires submission of a new PPAP. Am I wrong on this?
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A Sea of Statistics
Super Moderator
off the top of my it is Saturday night but this sounds tempting....
Sounds like you have many opportunities to excel, and shine....
1) likely need to re-PPAP, I would discuss internally and with your immediate customer rep
2) wow marginal GD&T...CMM results are dubious
3) regardless of part/assembly a 10-15 piece layout is mandatory as a minimum, and given the above history, a 1-15 part re-layout annually
4) Part, industry??...please share more info
5) just a off the top of my wine filled head suggestions

Thank you. It's automotive, and heavy machinery. Currently I am the only one capable of programming, and having time to do it is limited. Every time I mention making corrections, I'm immediately stopped by the quality manager. She believes continuing to do it wrong and not tell anyone is better than correcting the problem. Just two weeks ago one of the customers, through a series of events, found out the print was being violated through improper alignments. They were obviously angry. I had explained to our QA manager, the director of sales, and the GM for weeks prior, why that was a bad idea, and that we should fix the issues before running again. They insisted, "we PPAP'ed them like this and they accepted them so we're doing it like this again". I "believe" the customer simply approved the PPAP by reading it, and then let the parts sit on a shelf until a time they were needed (6 months or so). I pleaded for our company to come clean. It would look good that we were honest, and that at worst, we'd have to redo a 30 piece PPAP. I said we could attribute the problems to individuals who didn't work there anymore (entirely true). However, the new order was for 900pcs. I impressed upon them to examine which was the most efficient path to take. They chose to keep things hushed, and they got caught. Of course that created hours and hours of fruitless inspection by me, producing results to try and explain what I had been telling them for weeks. The program was wrong!

One of the problems with this company is that literally no one above me understands programming, or GD&T, and only one of them understands prints. The GM started on the same day I did three months ago, and this is his first position in a precision machine shop. He had one year experience in a foundry after college. Smart guy, but young and inexperienced. I have been programming for 20 years. He's not making all these decisions on his own. He's relying on advice of people who should know better. The other two people responsible for knowingly allowing this to continue, before he or I started working here. The QA manager, and the director of sales.

I am not suggesting these people are dumb, and that I'm of superior intellect, or a know it all. I make mistakes myself, for sure, but there are simply things that have obviously been done incorrectly by well intended, yet inexperienced persons before me that need to be corrected. I'm of the mindset that I don't pay the bills. If management wants to make decisions which they feel is in their best interest, then so be it. However, I think it's absolutely imperative that we first ensure we're doing everything correctly before those decisions are made. I have run into situations where an engineer had obviously draw something incorrectly, yet insists it must be done that way. Perhaps it's an alignment construction that's impossible to create. I see that on a regular basis. I can understand a company making the decision to do it correctly, and moving forward with that. I don't understand knowingly violating a correctly drawn print.


A Sea of Statistics
Super Moderator
OK, the wine happiness has subsided...based on a cursory review (it is Sunday AM....zzzz) and assuming the above assessment is spot certainly appears that by far your biggest challenge is NOT technical, process related...but an apparently deeply embedded corporate culture of " Così fan tutte...", my translation ...Thus do they all, in other words...."every one does it this way, and we continue to do so"....yours is a deep seeded cultural issue(s), so again, as a "Technical Professional"...endeavor to be concise, consistent, professional and somewhat diplomatic in pointing out the many errors of their ways. Having been in a similar situation, you may reach a point where....your conscience takes over, and or you choose to be heard, and not necessarily at that firm. In a larger sense the technical filed is overflowing of instances where solid technical recommendations and data were ignored for the greater good, of meeting our schedule....being first to the market etc...

Lastly, my expeirnece with mostly Tier 1 suppliers, is that the really good ones are the ones who are upfront/proactive, in problem identification, proposing containment and corrective actions...those discussions are at times unpleasant but a reactive stance is much less optimal.

I am a big proponent of SSBB, statistics AND GD& BB professor shared some simple info...."Data Are Impersonal...Opinions Are Not..."

My shared insights....hope this helps


Looking for Reality
Staff member
Agree with optomist regarding the culture...

Strictly for the CMM programming vs. PPAP, I would look at it as a risk/reward scenario.
How will you change the program? (Don't answer, consider for yourself).
If instead of to points defining a line, you shift to a best fit line through 100points its a pretty minor thing.
If you change the order of measurement, but measure each feature the same way using the same tool it's even more minor.
If you measure a best fit ID using vision capture in place of three manual points placed by an operator it is a massive change.

Anything that has a distinct chance of changing the measured value is a big, big deal.
Order of measurement is sorta minor.
Capturing correctly 99.9% of the time instead of 30%...but the capture method staying the same is pretty minor.
Once you've rated the likelihood of getting different results after reprogramming...then it's time to consider whether PPAP is a topic to broach.

I changed one of our programs with a stage shift to make it faster before the operator placed the manual point for "look here". Nothing else changed, and all data capture remained the same...not only did I not re-PPAP, I didn't even redo GRR.
When I had to significantly change the lighting to capture edges on a different color part, that got GRR and PPAP.


Mike S.

Happy to be Alive
Trusted Information Resource
Thank you. It's automotive, and heavy machinery. Currently I am the only one capable of programming, and having time to do it is limited. Every time I mention making corrections, I'm immediately stopped by the quality manager. She believes continuing to do it wrong and not tell anyone is better than correcting the problem.
I'm going to add one piece of advice to the above good advice: CYA

I don't know the application of the products you make, but regardless of that, if you see errors document them and if upper management refuses to correct them or do whatever is right, I would be sure to keep evidence to that effect. And by "keep" I mean keep personal copies of that evidence. Hopefully you will never need it, but if you do need it, you might need it bad.

And if there appears to be no chance to change that culture, I suggest looking for employment elsewhere.
Agree with optomist regarding the culture...

Strictly for the CMM programming vs. PPAP, I would look at it as a risk/reward scenario.


I really wish I had only the issues you're mentioning! The alignments are incorrect in most cases. Before my coworker left the company, he told me that he had to adjust alignments on one part to make it appear as though things were in tolerance. Literally, adjust for each part through the cmm, of the same part number! What's worse yet? He discussed this with, and got approval from management. He knew the program had to be rewritten, but they wouldn't allow that. I can't understand why this behavior is acceptable, but just making it right isn't.

Even worse, those parts are gonna be hitting again real soon, and I have no idea what changes were last made to this program. All I know is they were saved on the last run. *SIGH*

I'm not unreasonable. In twenty years, I have not worked in a shop that did it by the book 100% of the time. However, it was the exception rather than the rule.


A Sea of Statistics
Super Moderator
wow, sorry to hear sure sounds like they are gaming the system...scary, scary. It would seem as though your options are limited..

Mike S.

Happy to be Alive
Trusted Information Resource
Hermit, you are in a bad spot. I've been there, and I have some (metaphorical) scars to prove it. Just remember, don't be a party to something that may get you jail time, and be able to look at yourself in the mirror and like what you see.

My philosophy has been and remains that I'm gonna do it the best, most correct way I know how after considering all the available information. If you (my "superior" in the organizational structure) disagree and want to overrule me, you can, of course, but it's gonna be your signature that releases the product, not mine.

Sometimes people back down instead of putting THEIR signature or stamp of approval on something they know is bad; they are willing to have YOU do it, but they don't want to. Other times they are willing but are overruled by their superiors. Sometimes they do it.

Like I said, always CYA.


Looking for Reality
Staff member
to make it appear as though things were in tolerance
Sounds like you already know the answer to your own question (Do you need to PPAP?), and it looks like we all agree with you.
Now for the "How do I survive this with my sanity and my job?" part...
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