FMEA, CP, SPC & MSA relationships and links (APQP Elements)

Hello,

I need to know more details. about the relationships between the elements of PFMEA, CP, SPC and MSA.
All i know is relating to (mostly) special characteristics ( which must be the same in PFMEA and CP), but un auditor said that is more than that ( links beetween RPN and Gage R&R).
It would be better for me to have more informations on the subjects (articols, documents or links ).

Thank you!


PS A have few knowledge on SPC and MSA ( so any help is welcome).

The relationships are shown graphically and described in Basics of the APQP Process and Basics of an FMEA.

If you have more specific questions, we'll try to help.

I'm not sure of a relationship between PFMEA RPN and Gage R&R.

Marc said:

I'm not sure of a relationship between PFMEA RPN and Gage R&R.

Click to expand...

I don't see a "link" either. Come to think of it, I'm not sure there's a true "link" with SPC - other than directing you to a table of the Customer Specific (or AIAG) detection rankings (you either do it or you don't) and specifying the rank value. I''l have to ponder that one some more.

FMEA to CP to MSA?

Marc said:

I'm not sure of a relationship between PFMEA RPN and Gage R&R.

Click to expand...

Isn't the link, on my PFMEA I identify a high risk failure if a dimension is incorrect. Thus I need to be sure I measure it (put it on the Control Plan), thus I need to understand the ability of my gage system to provide useful information (MSA)?

Relation between Cp and Gage R&R (MSA - Measurement System Analysis)

PAGE 191 MSA Manual, Third Edition

Cp Act = Cp obs / Root Squate (1-(Cpobs*GRR)^2)

Therefore your GRR (MSA) is affecting to the Cp of your process, the Cp you have meassured is afected by the capability of the tooling.

jrubio said:

PAGE 191 MSA Manual, Third Edition

Cp Act = Cp obs / Root Squate (1-(Cpobs*GRR)^2)

Therefore your GRR (MSA) is affecting to the Cp of your process, the Cp you have meassured is afected by the capability of the tooling.

Click to expand...

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Couriously this issue is requeted in the PPAP level 3 as:

1) SPC (cp & Cpk) and
2) MSA (GRR) but all the times this studies are separated instead of conect both concepts.

We have meassure a Cp and Cpk of our process (SPC) with that tooling that have a GRR (MSA) given for this mentioned charasterist (Only), therefore the real Cp is not the obsereved, its need to be fixed by the desviation of the GRR aplying the formula given.

Due to the Cp real always be less than observed applyinfg the formula.
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Relation between RPN and Cp.

At first No relation.

RPN ia a number that lead us to a Control method to minimize the RPN which it is not neccesary be under Statical Control.

i.e: Visual inspection, Check gap

In case of Statical process X-R, you may define the reaction plan acording to Cp, Cpk.

But remember the Statical process shown in the PPAP need to be done with the parameter of the process marked as significand or Security and Controlled via Statical mode, no for all charasterists.

But a full considerartion: Only for SPC Control plan may be:

yes it exists a correlation between Cp and RPN due to:

RPN = Frecuency * Severity * Detection.

Frecuency = funtion of Cp.

Due to Cp is the probabily to fall in the specified limits, therefore a formula correlation both concept it could be easily deducted.......




bla bla bla......
RPN =

FMEA is a reliability tool used for preventing failures, when you have a high RPN # related to low propability of detection then you can use SPC in your process to boost your detection propability (low detection score) and your RPN will be lower.
Control plan lists all charactaristics (critical and non), and specifies the specification and how it is controled in the process including how to inspect, where, how many and in what frequency. MSA tells how do you measure the performance of your proces taking into consideration R&R.