Quality Plan Review

A regular review of the plan will save money

A strategy for using statistical process control .​

  1. A well set up process,                                                     (use Minitab to process data)
         accuracy and precision are vital before the process starts;  without that, there will
         be little hope of delivering today’s levels of quality

  2. … stable,                                                                  (use Infinity to process data)
         common causes must be controlled or eliminated, otherwise variability over  time
          will cause defects once more and charts will not be helpful.


  3. … which checks critical features,                                                (use process map)
         are you sure that the parameters you measure are still critical?  
         Processes  have changed significantly over the last few years.


  4. with minimum quantities of samples,                           (use Minitab to estimate n)
         what science did you use to decide on sample sizes? You may be measuring
          too many samples and wasting money, or too few and making poor decisions

  5. … at suitable frequencies,                            (use history and risk from process map)
         is the frequency of checks decided by risk, or plant convenience?

  6. … to ensure there is no significant change,                (use Infinity to process data)
         how many non-quality people realise that the qc check is not to check that
         the production is in specification; it is to check it has not changed since set-up.


  7. whilst continuously improving the process to eliminate variability.                                                                                             (use Minitab to process data)
         variability is a major cause of poor quality.                              

The key implications of this are:


  1. Manage the process by risk, controling only those parameters which truly are critical; these change from time to time.

  2. Understand how parameters influenece the process, to ensure you can stabilise the process.

  3. Use control charts as problem solving tools and later on to spot change; that is how Shewhart used them.

  4. Nurture a culture of continuous improvement.