Unilateral Tolerance Capability - Shaft Runout - Which capability index to use?

A

Al Dyer

#1
Does anyone have some ideas on which capability index (s) should be used when monitoring runout on a shaft with a unilateral?
 
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S

sbnorris

#2
Al:
I have run into the same question. I think using (mean+3s)divided by the allowable tolerance is a valid way of expressing the capability of such a process. But I am not sure if this a valid approach.

Originally posted by Al Dyer:
Does anyone have some ideas on which capability index (s) should be used when monitoring runout on a shaft with a unilateral?

ASD...

 
D

Don Watt

#3
Hi Al,
I tend to use PpU / CpU ;
(Upper spec limit - double bar X) divided by 3 sigma to give capability of making parts within maximum tolerance.

Does anybody know if there is a "target figure" for this index, e.g. Cpk >1.33 / Ppk >1.67 ?
 
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