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XBar-R Chart Usage

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  • #46274

    Lee
    Participant

    I’m teach an introductory class on quality, in an industrial setting and teaching production workers, and am interested in understanding the degree of coverage I have for specific areas.
    In the area of control charts I cover the use (not generation) of XBar-R charts.  That covers about 95+% of the applications in this plant.  Any estimates of how adequately that prepares the participants for work in other plants?  In other words, of all of the forms of control charts, do you have an estimate of how often xBar-R charts are used compared to the total of all options for plants in general?  I suspect that hard numbers do not exist, so your input is valued.

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    #152714

    Krishnam Raju PV
    Participant

    Hai
    This is Krishnam Raju
    When to use X-bar R charts
     
    If any process 6 six sigma (standard deviation) = Tolerance     use X-bar R charts
     
    Example
     
    Shaft Outer diameter Spec. 15.00 to 20.00mm (Tolerance = 5.00 mm)
     
     Collect 30 parts and measure Outer diameter and calculate standard deviation.
     
    Assume that standard deviation found 0.80mm
     
    Calculate six sigma (6 standard deviation) = 6×0.80 = 4.80mm
    Therefore Six sigma (6 standard deviation) = less than tolerance (4.80 is less than 5.00mm) then use X bar R charts.
     
    I hope the above information your question answered.
    If any question please ask me.
    Krishnam Raju

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    #152715

    Darth
    Participant

    Your post was babbling nonsense.  As for the original post, xbar/r charts are the most common in high volume manfacturing processes since rational subgroups are pretty easy to identify.  Depending on what you are measuring and the frequency in which data occurs, you will find that I/MR charts are quite popular as well.  It might be useful for you to also cover the basic attribute control charts like the p-chart.  It is also quite popular and allows for the distinction between measuring continuous data and attribute/discrete data.

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    #152722

    D D
    Participant

    As Darth says, this is utter babbling nonsense.  Forget six sigma, go back to basics:
     http://www.spcpress.com/pdf/Wh_Make_PBC_Work.pdf

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    #152724

    Mike Carnell
    Participant

    Darth,
    I take about a month off (from the Forum) and come back to find the same silver tongued devil posting. Glad to see you are still spreading wisdom.
    Regards

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    #152734

    Lee
    Participant

    What I was looking for was something of the below format (but have not yet seen it):
    IMHO, XBar-R charts : 80% of the time, Attribute charts: 15% of the time, ImR Charts 5% of the time. 
    So, in practical across the industries in the US/World, what is your humble estimates of the percentages?

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