Capability Study for Level 3 PPAP - They are asking for a 100 peice capability study


1236 Paul

I have just completed a level 3 ppap for a customer (first one I have done) and they are asking for a 100 peice capability study, I don't know what this is, can anyone steer me in the right direction. Thanks. Paul


First, you'll need to know what characteristic(s) are "critical." In other words, what dimension are you to do a capability study on? Once that is established, you need to collect 100 samples (parts) to preform the study on. Now, you say that you've just completed the PPAP, so I'm assuming that production ran some quantity of parts. Let's hope that they ran at least 300 pieces, since that is the minimum required in the PPAP manual. You take your 100 pieces out of that production run. If possible, samples should be taken over time ( some from the beginning, middle & end of the run.) You then would measure the 100 pieces,(remembering the 10x rule.) At this point, I would enter the numbers into a software system which calculates & reports Cpk/Ppk information. If you don't have software, I guess you're going to have to do it the old fashion way, paper & pencil. Formulas can be found in the PPAP manual. You'll also need a Gage R&R for the piece of measuring equipment used for the study. In the future, might I suggest that PRIOR to the PPAP run, the "critical characteristics" are identified and a plan is established to collect data on the floor at the time of manufacturing (ie; xbar & r chart.) Then all you have to do is collect the data from manufacturing & crunch the numbers. Hope this has been of some help. If you give me more specifics, I might be able to "walk you through" this capablity study. Good luck, and may the force be with you :).

Don Watt

Nice summary for capability study, just one question ....... What's the 10X rule?

gerard jordan

paul, just a few points though by now i'm sure you've attended to the matter. sounds like you had some good advice from fellow netters. On point of control charting etc make sure you do this manually and not via some software package. Do this for some time it's the only way to learn on such matters.
Secondly, make sure that process operators become involved in this process, ie, they contribute their wealth of knowledge and experience in determining what makes the process tick (ie, causes of varuiation)..
Thirdly, before you undertake to determine process capabilities you must firstly acknowledge whether or not the process is stable else all other efforts could prove futile.finally,is there anyone else in the plant who could undertake this study? If there isn't then something's wrong!
good luck with everything anyway.


What I meant by the 10x rule is to be sure that the piece of measuring equipment used has resolution to one decimal place beyond the specification you're measuring. In plain english if you need to measure something .xx inches, you need a tool that will measure out to .xxx.
I've probably made that as clear as mud! You'll have to excuse me, Delphi has been using me as their whipping boy this month!
I'm not sure if I should s**t or wind my watch!
Anyways, back to the group....
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