Posts: 70
From:Notts,United Kingdom
Registered: Mar 2000

posted 06 April 2000 05:59 PM               

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Hi,
I'm relatively new to Quality in Manufacturing and I'm trying to establish how often we need to do a confirmation check on parts from a grinding process.
Is there any recognised correlation between process capability indices and inspection.
e.g. for a Cpk <1.33 recommended minimum inspection frequency = 1 in 50 ?

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Posts: 4119
From:West Chester, OH, USA
Registered:

posted 08 April 2000 09:26 PM               

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Not that I know of - maybe one of the experts can comment on this.

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Posts: 244
From:
Registered: Sep 1999

posted 10 April 2000 08:50 AM               

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No expert here,but,I will make the assumption that you are using SPC charting. If so, and the process is in statistical control, then there is no defined interval. Watch the chart for trends and act accordingly.
On the other hand ,if you are asking how many times do you check and record on the chart; minimum of once per shift. IMO I would use sampling based on number of parts produced to determine how many times to take a subgroup.
Don has some excellent articles on his web site for sampling.

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Posts: 498
From:Tullahoma, TN
Registered:

posted 10 April 2000 09:53 AM               

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Is there any recognised correlation between process capability indices and inspection. e.g. for a Cpk <1.33 recommended minimum inspection frequency = 1 in 50 ?

As far as I know, there is not a recognized relationship between process capability and sample frequency. This is probably best defined by your process.

Regards,
dWizard

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