iSixSigma

dart chart

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  • #32489

    vidyut bapat
    Member

    I find Dart Chart is quite useful to plot data in the form of xbar / sigma. I want to know how popular is this mode of representation.
    Do you also use Dart Charts?
    Vidyut Bapat

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    #86832

    Marc Richardson
    Participant

    Vidyut,
    Years ago, I published an article in Quality Magazine titled “Qualitarget”. It looked like a target with a green bull’s eye (center) surrounded by yellow and green concentric bands. The operator plotted individual measurements on the chart and then interpretted for control. It eliminated the need for the operator to perform calculations. Does this sound similar to the dart chart? Please provide us with a description.
    Mar Richardson
    Sr. Q.A. Engineer

    0
    #86879

    vidyut bapat
    Member

     
     How to plot Dart Chart –
     Plot average on X axis and sigma on Y axis.
    Your target is zero sigma at specified average ( on X axis).
    The triangle lines with USL and LSL on x axis as base and various sigma value as height are loci for corresponding Cpk values.
    Cpk improves as triangles become smaller in height.
    Here is an example –
    (The picture is missing)
    Let me know youe e mail, where I can send details
    Vidyut Bapat
     

     
     

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    #86882

    Shree Phadnis
    Member

    Dear Vidyut,
    Thanks a lot for the input.I want to share an important thing .In one of my consulting assignments I actually stopped the prctice that was used of dart charts in the manufacturing process primarily because it provides no information on understanding variation, which is paramount in anderstanding any process.There also exists a ststistical flaw in calculating the CPK of the process based on the dart chart , that is primarily based on how the standard deveation is measured.I have seen this mistake beeg made by far too many practitions who calculate the Cp or Cpk based on sample standard dev, without using control charts.to sum, you cannot calculate cpk of a process if it is plauged by special causes and to undrestand the type of variation you will have to primarily use control charts.

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    #86939

    Marc Richardson
    Participant

    Vidyut,
    Here is my email. I’d be happy to send you more information regarding Qualitarget. Just let me know.
    [email protected]
    Marc Richardson
    Sr. Q.A. Eng.
     

    0
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