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Help with Spec Calculation

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  • December 1, 2005 at 5:44 pm #41601

    Clowers
    ★ 10 Years ★
    Participant

    Hi all, I have a question. 
    I have an assembly machine that records data readings (pressure measurements) on specific parts.
    The Engineering spec for the parts produced says the specification on the machine  is to be X-bar +/- 4 Sigma.
    If I take 30 or 50 readings from the machine and find X-bar, how do I calculate the UCL and LCL.  with the +/- 4 sigma.
    Thanks,
    Kathy
     
     

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    December 1, 2005 at 6:27 pm #130594

    Akram
    ★ 10 Years ★
    Participant

    Control charts usualy use 3 instead of 4.

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    December 1, 2005 at 7:09 pm #130597

    Andejrad Ich
    ★ 10 Years ★
    Participant

    Regarding your question, please refer to my response to a similar, neighboring topic.
    https://www.isixsigma.com/forum/showmessage.asp?messageID=84292

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    December 1, 2005 at 7:52 pm #130603

    Ron
    ★ 10 Years ★
    Member

    You are mixing specified limits with control limits.

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    December 1, 2005 at 8:06 pm #130607

    Andejrad Ich
    ★ 10 Years ★
    Participant

    …please read again;  I’m the one distinguishing specified limits from control limits. 
    Andejrad

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    December 1, 2005 at 8:35 pm #130610

    Clowers
    ★ 10 Years ★
    Participant

    Thanks for the help all.
    If I understand it right I need to multiply the standard deviation by 4 then add and subtract by X-bar.
    Thanks again

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    December 1, 2005 at 8:59 pm #130611

    Williams
    ★ 10 Years ★
    Member

    That’s all!

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    December 2, 2005 at 1:21 am #130621

    Ron
    ★ 10 Years ★
    Member

    You afre right, Sorry for the mistake.

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