Monitoring and Measurement of Manufacturing Processes - TS 16949 Clause 8.2.3.1

[glennb185]

I would like some opinions and feedback regarding TS clause 8.2.3.1.
I have simple manufacturing processes and use Xbar and R charts to monitor the output. The output has little within subgroup variation with cp and cpk values over 2 and very narrow Xbar control limits. Occasionally I will see variation in the incoming material over time that causes a small process shift. The small process shift causes the Xbar values to be outside the limits. The output is stable but shifted and even with the shift I have high cpk values and acceptable ppk values. If I perform a traditional capability study and chart 25 consecutively produced subgroups the process shows good stability as this over time variation in the incoming material is not present (yet).
If I read clause 8.2.3.1 literally, “reaction plans shall include containment of product and 100 % inspection, as appropriate”,
Is this an instance where 100% inspection is not appropriate?
Is this phrase intended to be applied to ongoing monitoring of process output, or is it intended to be applied when conducting an initial process study?

 

[Marc]

A quick "Bump". My Thanks in advance to anyone here who can help with this one.

 

[Jen Kirley]

Good day glennb185,

I do not believe the intent of 8.2.3.1 is to force 100% inspection on items that are experiencing a process shift and yet are themselves still conforming. If a tight process spread (as described in NIST page What is Process Capability?) shifts to one side but products are still within or near upper or lower limits, I'd say the key weasel words "as appropriate" apply. Consider what NIST has to say about evaluating process capability for a process that has gone off center: Assessing Process Capability.

That said, I think the next question could be why we are willing to accept this kind of variation from a supplier. Can the issue be resolved so you can both enjoy a strongly capable process?

I hope this helps!