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The CORRECT steps to implement an SPC chart

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Posted 17th November 2010 at 11:46 AM by bobdoering
Updated 22nd November 2010 at 05:27 PM by bobdoering

You might have had some SPC training in the past, but it probably skipped over the correct steps to implement charting on the shop floor. Check it out, here they are:

1. Develop the total variance equation (Yes! This is the very first step!)

2. Determine which variance factors are adjustable, which are noise, and which can be set as a constant.

3. Minimize the variation of each of the participating variables - get the process in a steady state and capable. This includes eliminating your "special causes".

4. Accurately determine the correct distribution of each of the remaining variances

5. Determine which of the remaining variance factors you are going to chart

6. Pick the correct chart to evaluate that variance factor (variable)

Did anyone share that with you in your SPC training? If not...you missed out on the important stuff...

Don't feel bad, it's common.
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Comments

  1. Old Comment
    Bob;

    I have to hand it to you, you always get me to think! Thanks! A terrific addition to the steps you stepped out was the additional questions asked by Dorian Shainin: Is the primary variance within part, part-to-part, or lot-to-lot! Thanks again for the post!
    Posted 18th November 2010 at 04:20 PM by Sturmkind Sturmkind is offline
  2. Old Comment
    bobdoering's Avatar
    One of the points I have made elsewhere in the cove that shows the importance of the Total Variance Equation is that it is the true origin of 6 Sigma. Sigma - the standard deviation - is the square root of the variance. So, therefore, the square root of the sum of all of the variances shows the critical importance of knowing what the factors of variance are to the proper implementation of the 6 Sigma tools. I bet you rarely see that in 6 Sigma training!

    Whats more, it shows that virtually all processes are multi-modal - unless you can eliminate or make statistically significant ALL (or all but one) of the total variance factors! Unfortunately, the ones usually not minimized (and therefore masking all others) - is measurement and gage errors. They are typically normal, giving the false facade that the underlying process is, too - and that all of the normal statistics apply.
    Posted 18th November 2010 at 06:31 PM by bobdoering bobdoering is offline
  3. Old Comment
    selena15's Avatar

    spc

    thank you bobdoring
    very interesting
    have nice week end
    selena
    Posted 25th February 2011 at 09:47 PM by selena15 selena15 is offline
  4. Old Comment
    Hi Bob,
    Can you share one particular example? To enlighten me more.. Hope you can...thanks!
    Posted 20th July 2011 at 04:33 AM by Erick Mirabel
  5. Old Comment
    bobdoering's Avatar
    Quote:
    In Reply to Parent Post by Erick Mirabel View Comment
    Hi Bob,
    Can you share one particular example? To enlighten me more.. Hope you can...thanks!
    Good idea. It will take some time to put an example together, but I will do that and add it to the blogs.
    Posted 20th July 2011 at 11:36 AM by bobdoering bobdoering is offline
  6. Old Comment
    what is the difference between ISO 9001-2008 and TS 16949?
    Posted 2nd December 2011 at 01:45 AM by bukee
  7. Old Comment
    bobdoering's Avatar
    ISO-9001-2008 is a generic quality system specification, where TS 16949 is specifically for the automotive industry.
    Posted 2nd December 2011 at 10:38 AM by bobdoering bobdoering is offline
  8. Old Comment
    understand that, our company is looking into TS 16949. Guess what I wanted to ask was, how much of an upgrading do we need to do to pass/get certified TS 16949?
    Posted 2nd December 2011 at 10:51 PM by bukee
  9. Old Comment
    bobdoering's Avatar
    The move from ISO9001 to TS 16949 is very significant, with much more documentation overhead, and many more customer specific requirements no even listed in the requirements. It is extremely comprehensive, and will take much more resources to implement and maintain. Only do it if you are required to. You may want to get a gap analysis before deciding to dive in.
    Posted 5th December 2011 at 03:54 PM by bobdoering bobdoering is offline
  10. Old Comment
    Hello,
    Can anyone help me with some excel file that is calculating Cpu, Cpk, Cp, PPM, and staff like this and is also doing a bell curve with the histogram for thinghs like flatness or perpendicularity ?
    Posted 27th February 2012 at 06:27 PM by calin.furdui
 

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