CPK analysis based on subgroup - s-chart & R-chart

WebDesignesCrow — Fri, 09 Jun 2023 00:47:54 GMT

Hello Experts,

I'm doing some Cpk calculation method validation for our process versus AIAG guidelines.

Some background, I initially run 300 samples to setup a baseline using JMP - Cpk calculated is using I-MR (based on capability analysis at distribution).

Our production line is using x-bar & R-chart for n=10 for 14 batches (with 1 batch outlier).

Means, our production sample 10 measurement for each batch & SPC chart was monitored using Excel including the Cpk.

I want to show them that they should x-bar & s-chart per AIAG guideline & what will happen if they use s-chart or what would be the Cpk if the process stable.

When I ran the data with subgroup ID using JMP, the Cpk calculated is based on I-MR (photo below):

Since R-chart, s-chart or MR are just used as std. dev estimates (using formula R-bar/d2), how can I configure JMP to calculate the capability analysis using R or s when I want to?

p/s: I don't really buy to this argument on which Cpk method is correct because all method are correct based on our own process scenario/interpretation (SPC is the champion to do improvement) but AIAG put it in their guidelines, so I need to know how to calculate the capability analysis using R or s with JMP .....

Any tips very much appreciated and I use JMP 15.

Re: CPK analysis based on subgroup - s-chart & R-chart

tonya_mauldin — Tue, 12 Apr 2022 13:08:43 GMT

You can use the Process Capability platform. Here is some code that shows how to create a capability analysis where within sigma is estimated by the average of unbiased standard deviations.

dt=Open("$SAMPLE_DATA/Semiconductor Capability.jmp");
Process Capability(
	Process Variables( :NPN1[:wafer] ),
	Within Subgroup Variation( Average of Unbiased Standard Deviations ),
	Individual Detail Reports( 1 ),
	Capability Box Plots( 1 ),
	Goal Plot( 1 ),
	Capability Index Plot( 1 ),
	Process Performance Plot( 0 )
);

topic CPK analysis based on subgroup - s-chart & R-chart in Discussions

CPK analysis based on subgroup - s-chart & R-chart

Re: CPK analysis based on subgroup - s-chart & R-chart