#### vitplanocka

##### Registered

Hello,

can anybody please advise with the situation below. I tried seaching the forums but didn't find anything relevant.

We are producing a steel part that has 3 important geometrical characteristics A, B, and C defined in a drawing.

A, B and C are correlated, so we can, for instance, adjust the mean value of A in the process but this also changes mean values of B and C.

Customer require us to submit Cpk/Ppk for A, B and C.

Even if we adjust the process so that Cpk/Ppk for A exceeds e.g. 1.33, the capability indices for B and C will become low (because B and C will not be centred). Same thing happens if we adjust for B or C.

So we are struggling to submit to customer Cpk/Ppk > 1.33 for all 3 characteristics.

What is a strategy that is in practice used for such correlated characteristics?

Thank you,

Vit

can anybody please advise with the situation below. I tried seaching the forums but didn't find anything relevant.

We are producing a steel part that has 3 important geometrical characteristics A, B, and C defined in a drawing.

A, B and C are correlated, so we can, for instance, adjust the mean value of A in the process but this also changes mean values of B and C.

Customer require us to submit Cpk/Ppk for A, B and C.

Even if we adjust the process so that Cpk/Ppk for A exceeds e.g. 1.33, the capability indices for B and C will become low (because B and C will not be centred). Same thing happens if we adjust for B or C.

So we are struggling to submit to customer Cpk/Ppk > 1.33 for all 3 characteristics.

What is a strategy that is in practice used for such correlated characteristics?

Thank you,

Vit

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