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Process capability

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  • February 16, 2009 at 5:42 pm #51865

    Arturo Mendiola
    ★ 10 Years ★
    Participant

    How can I estimate the total process capability of a series of different processes?

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    February 16, 2009 at 5:47 pm #181241

    Nolan
    ★ 10 Years ★
    Participant

    You can look up the defintion of “Process Capability” and apply it.

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    February 16, 2009 at 5:56 pm #181243

    Arturo
    ★ 10 Years ★
    Participant

    Thanks for the reply Les,
    I understand the definition of process capability, and I know how to apply it to one specific process; but I need to know how to estimate a process capability for a series of different processes, imagine I have a welding operation and then a soldering operation and then a sawing operation, all of them using the same spec limits; I know how to estimate the individual cpks for each operation but I want to estimate the cpk for the three of them, have you seen something like this before?
     
     

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    February 16, 2009 at 6:35 pm #181246

    Nolan
    ★ 10 Years ★
    Participant

    Arturo, it’s the same as calculating PC for a single step process. That is, you have spec limits for the final product – you have results for the final product – calculate Capability.
    It doesn’t matter how many processes, or steps, are involved in getting to the final product, if you want Process Capability for that “overall” process then deal with the output of that process.
    Does that make more sense?

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    February 16, 2009 at 6:53 pm #181250

    Obiwan
    ★ 20 Years ★
    Participant

    You could also apply the concept of Rolled Throughput Yield to these steps…after all, a capability analysis is nothing but an attempt to get to the number of good products coming out of a process..and RTY does the same thing.
    Obiwan

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    February 16, 2009 at 7:05 pm #181255

    Arturo
    ★ 10 Years ★
    Participant

    I was thinking something like RTY for CPks like Obiwan mentioned, how should I do it?
    should I only convert ppms from the cpks into FPY for esch operation and then calculate RTY or there is a way to do it using cpks values?
     

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    February 16, 2009 at 7:06 pm #181256

    Obiwan
    ★ 20 Years ★
    Participant

    I would not get hung up on CpK values…just figure out how many parts the process is wasting and what is causing that waste…then eliminate the cause.
    Obiwan

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    February 16, 2009 at 7:12 pm #181257

    Arturo
    ★ 10 Years ★
    Participant

    I’m looking for a way to present the picture to the customer who actually owns the process.

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    February 16, 2009 at 7:15 pm #181258

    Obiwan
    ★ 20 Years ★
    Participant

    OK…fair enough…but why CpK’s?  Why not say that this process is currently producing XXX out of XXX defective products?  Or say XX% of the products produced by the process are defective?
    Those are generally much easier to understand to people than CpK.
    Obiwan

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    February 16, 2009 at 7:23 pm #181259

    Arturo
    ★ 10 Years ★
    Participant

    I was looking for different alternatives but looks like RTY will work, I just wanted to make sure I was not missing something or a different way to do it.

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    February 16, 2009 at 7:32 pm #181261

    Schuette
    ★ 10 Years ★
    Participant

    Hi Obiwan,
    How are you? If you don’t mind me asking; are you still with BOA? How Six Sigma Program and Quality & Productivity groups are doing now at BOA?
    Best Wishes,
    Jim

     

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