do the Cpk and SPC analyse

本帖最后由 baqiao2001 于 2009-9-10 18:25 编辑

As we all know, more and more companies are required to do the Cpk and SPC analysis so as to improve their qulaity capability and meet customer expectation. I think there are maybe three reasons: The first one is that Cpk is the index of a supplier’s present quality capability, do this analysis can predict a supplier’s future potential quality performance. So lots of companies define the Cpk can be accepted unless it’s above 1.33. I think there is another meaning to do the Cpk analysis, that is we can combine the Cpk with the DOE together. At the beginning, we can require the supplier to do the Cpk for some critical dimensions which come from the former experience or engineering requirement. Then if Cpk can’t meet the requirement, we can do the necessary analysis and co-work with supplier to find out the critical factors that influence the Cpk performance, in this phase DOE would be a very useful quality tool to identify the potential critical factors and can optimize the best reasonable interval of these selected factors. After that, we can define the process parameters for the worker to follow up . I believe by doing this can increase one’s Cpk and true quality performance. But as far as I know during my past limited working experience, it is a pity that most of companies only do the Cpk analyse by calculating the Cpk result but not to deeply research the reason why .The second reason to do the Cpk/SPC analysis is that most of the company define in their document that they would do the Cpk/SPC analysis both in their company and also at their supplier side . “We must do what we say in the document” so in this way, do the Cpk /SPC analysis is to meet the document requirement.The last reason is that by doing the Cpk /SPC analysis is a way to help and train the supplier to form a good habit, which is very important to supplier management.