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Die Switchover Control Chart

Six Sigma – iSixSigma Forums General Forums Tools & Templates Die Switchover Control Chart

This topic contains 5 replies, has 4 voices, and was last updated by  Chris Seider 1 year ago.

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  • #55887

    Boris Jarcevic
    Participant

    Hi everyone, cuurrently I am constructing individual and moving range Control chart for time consumed during exchange of die in Extruder line. As current state is highly unstreamlined and unpredictable there happens to be wide Control limits for individuals due to high range average. Consequently all points drop within control limits. How How to evaluate that kind of process? Poor but stable?

    #202033

    Strayer
    Participant

    It appears that your control chart is confirming something you already knew. A basic principle is to use DMAIC. Control charts are most useful during C. In short, find out why the range is so wide and do something to narrow it.

    #202034

    Chris Seider
    Participant

    @Straydog Hope you were trying to generate blog traffic. There are some very passionate folks that LOVE using SPC as an investigation tool in the Measure/Analyze phases.

    I have used it in the M,A,C phases myself. I find the use in measure phase QUITE useful when the folks have no ideas about variation causes or sources in their process.

    Thanks for the banter as always.

    #202040

    Strayer
    Participant

    @cseider You might convince me that SPC is useful in the A phase, after you have reasonably reliable data. Before that a control chart with questionable data can lead you down the garden path.

    #202043

    Ahiru-san
    Participant

    For this sort of thing, I like to just use the average time. The system isn’t IN control yet, so a control chart won’t be able to tell you when it goes OUT of control. In that case, some good old descriptive stats might get the attention of your audience.

    * The Range is 45 minutes with some changes taking 10 minutes, and others taking 55 minutes.
    * The Mean time is 30 minutes.
    * The Standard Deviation is 18 minutes.
    * The Future State goal is 9 minutes.

    Descriptive Statistics are pretty easy for most folks to understand.

    #202044

    Chris Seider
    Participant

    Interesting perspective…

    I don’t understand the statement “SPC won’t tell you when the system is out of control”.

    I suspect I know your intent but SPC is a tried and true technique to know when things are statistically showing evidence of being out of control (with an alpha error of course).

    Yes, your statement that descriptive statistics are great but don’t forget that time series plots and histograms are super also to help understand.

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