Lean production is built on the explicit assumption that each step is operated predictably and capably. Predictable operation can only be achieved and maintained by using process behavior charts. But short production runs make it hard to see how to use process behavior charts in a lean environment. So what can be done? Last month I presented the zed chart for individual values. This month’s column will illustrate the difference chart for individual values.

Short run charts

Process behavior charts are primarily concerned with characterizing process behavior rather than estimating process parameters. Because of the conservative nature of three sigma limits we can make these characterizations using relatively small amounts of data. This was illustrated last month with the zed chart. This column illustrates the difference chart for individual values. 

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