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EWMA – Jim

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  • #29270

    Mike Carnell
    Participant

    Jim,
    I am glad someone finally got the message that it wasn’t about the best tool academically. Unfortunately you hit right as the string fell off the list.
    Good Luck

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    #74571

    Annonymous
    Participant

    Jim and Mike –
     I think the EWMA discussion provides a great example of one of my recent favorite sayings. Useful in 6 Sigma work, too.  Especially when it comes time to actually implement and control process changes.
    “In theory, there is no difference between theory and practice.  In practice, there is.”

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    #74573

    Mike Carnell
    Participant

    Annonymous,
    I like that. Can I use it? (do I need to cite someone so I don’t get sued?)

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    #74575

    Anonymous
    Participant

    EWMA, along with other advanced tools such as Multiivariate SPC can (and has been) successfully implemented in practice if the following are in place:
    1. Automated procedures in software. For engineers, Minitab or JMP macros need be written to make it as simple as a button push.  For production, the algorithms need to be be ported into the production SPC software.
    2. Simplified training – you don’t have to tell the operators what the formulas are. They just have to know how to respond.
    3. Current SPC should be in place – this should be an improvement to an existing system.
    In my experience the operators (when trained properly) prefer an EWMA system over a classical Shewhart + WE rules system – its easier to use. Engineers (when trained properly) love the flexibility of the EWMA.
    Just my 2 cents.  Oh and speaking of money, EWMA saved my client several hundred K due to improved response time.

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    #74578

    Annonymous
    Participant

    I first borrowed it from a lawyer / psychologist who said it came from her favorite professor.  She did not name the professor, or the field or school in which he/she taught.  So I think it’s one of those sayings that can be used by anyone without formal attribution.  
    Please use it wherever you find it relevant.  It handily encapsulates the value of actually DOING almost anything.  I find it’s sometimes necessary to emphasize the need for direct experience vs.perpetual analysis.
     

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    #74579

    Mike Carnell
    Participant

    Annonymous,
    I can buy into most of this but I think the criticality of point #3 needs to be stressed. It isn’t a chart I would use in a moderately successful program.
    You might even be able to launch a program that started with this easier than trying to upgrade a shakey system.
    In terms of an automated SPC system, I really have never seen one that runs as well as the one that still does the calculations by hand. It lets people ignore the system to easily.
    I had a factory in Chicago once that had an automated system. The chart proliferation was insane – 1200 charts when I got there. Over 4000 OOC points per week. It was impossible to react to anything (many of the charts were just set up incorrectly). If this was done without the system then it would have never happened.
    I got a report (printout) of every point on every chart weekly – like I could do anything with that. What I did find was a lady who entered in under the comments section “Does anyone read this ___ report?”
    With afew hours of training she was an SPC auditor and we started investigating poorly designed charts. Got it down to 900 before I left – still to many.
    After that lengthy diatribe on automated SPC – I think it is dangerous. As you did say it enables a more sophisticated type of chart.
    The other point is since it is sensitive to small changes the measurement system must be able to make the measurement in a shop floor environment and still pass an MSA.

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    #74583

    Annonymous
    Participant

    Look out, Mike. There are two anonymous participants int his discussion now.
     

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    #74600

    Mike Carnell
    Participant

    Annonymous,
    Thanks for the warning. I know there is another consultant that uses the same “nn.” He participates under several names.

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