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    I would like to move from conducting batch release to spc on my process. this would reduce the number of samples and cost. do i need to validate the process in any way before i swithc. i gave run data for 20 batches and have calculated my control limits from this using minitab. should i use the mean and 3 sd for the control limits.
    any tips watch outs would be appreciated. how do i calculate the sample size for testing. my bach size is ypocally 150 units.


    vincent Piccirelli

    Usually the customer wants to see a capable process, 1.33 Cpk minimum. If it is a special characterisits then it could be 1.50 to 1.67.
    Either way, A capable process is a big step to get away from batch hold/release.
    Do you have a Exit Stratagey/Plan with team members and action plans? If not you can bet the customer will be asking for one. If they don’t then you can make one up and impress them with it.
    I hope this helps some.



    Look under the Tool and Template heading on the big blue bar to your left under control charts, it will give you good information. Points to note:

    Chart type depends on data type and sample size constantcy
    Number of samples (k) should be around 25 or more
    There is no hard rule on sample size (n)…depends on several factors
    The key is to minimize the variation within samples in order to see the variation between them….this usually entails small samples using consecutive observations
    Chose the chart based on data type and what makes sense relative to the characterisitcs of your data set
    Good luck.

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