Al,
I believe formula needs to be modified as below since it misses "absolute" value. Am I correct?
cpk = abs(mean - closest_limit) / (3 * sigma)
abs = absolute value
mean = average of the measurements
sigma = standard deviation
Best Regards,
Shahed
-----Original Message-----
From: [log in to unmask] [mailto:[log in to unmask]]
Sent: Friday, December 03, 2004 7:52 AM
To: [log in to unmask]
Subject: Re: [TN] Cpk calculation for registration
Parial,
Don't know enough about your process, but from a statistical point of
view, simply - Cpk is equal to the distance from the process mean to the
nearest spec limit divided by three times the standard deviation:
Cpk= (process mean - nearest spec limit) / (3 std. dev)
That being said, Cpk should always be greater than 1.0, or you have a
problem.
So, if you can measure the registration of the drilled holes, and have a
spec, you're set to go.
Good luck,
Al Kreplick
Sr. Mfg. Eng.
Teradyne, Inc.
500 Riverpark Drive
Mail Stop NR500 1-1
North Reading, MA 01864
Tel: 978-370-1726
Parial Swati <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
12/02/2004 11:06 PM
Please respond to TechNet E-Mail Forum; Please respond to Parial Swati
To: [log in to unmask]
cc:
Subject: [TN] Cpk claculation for registration
Dear friends,
Any ideas about the ways to calculate the Cpk value for registration of
the
drilled holes with the inner layers.
Regards,
Swati...
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