Has anybody achieved 6 Sigma?

Six Sigma – iSixSigma Forums Old Forums General Has anybody achieved 6 Sigma?

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    Thomas C. Trible

    Those who are interested in a deeper leraning should read “A Japanese Control Chart” by Don Wheeler. Dr. Wheeler describes the actual manufacturing results of Tokai Rika Co. The control chart limits were calculated in the usual manner X-bar and R. No data shown was ever out of specification limits. Periodically the process went out of control. Relative to the distribution of the manufacturing process, “The specification limits were 30 (and 30 is not a mistake here)standard deviations wide, and the process was properly centered relative to those specifications.”

    In terms of dimensions, the product specifications were 15.90mm, plus-minus 0.15mm, or from 15.75 to 16.05. However, “The spread of the natural process limits was 0.06mm.” That would correspond to a standard deviation of about 0.01mm. That would produce product from 15.87 to 15.93mm. Tokai Rika produced “0” defects – using, I might add, a control chart based on the Shewhart 3 sigma limits. These folks continually worked at keeping the process stable – and never had defects.



    Use of Poka Yoke tooling and fixtures in our mechanical assembly plane means that certain key sub assemblies are made with zero defects. Supplier integration and Poka Yoke mean we produce these assemblies and use them with no testing or inspection.

    The rules are be different for machined turned parts, due to tool wear etc. This is the best example i can give of how we have achieved Six Sigma quality on attribute products that either work or do not.

    Sam Meeuwissen
    Production Engineer.
    Six Sigma Blackbelt.

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