In theory, a production process is always predictable. In practice, however, predictable operation is an achievement that has to be sustained, which is easier said than done. Predictable operation means that the process is doing the best that it can currently do—that it is operating with maximum consistency. Maintaining this level of process performance over the long haul can be a challenge. Effective ways of meeting this challenge are discussed below.

Some elements of economic operation

As argued in “What Is the Zone of Economic Production?”, to speak of the economic operation of a manufacturing process, all of the following elements are required:
Element 1: Predictable operation
Element 2: On-target operation
Element 3: Process capability achieved (Cp and Cpk ≥ 1.5)

The notions of on-target operation and process capability are inextricably linked to predictable operation—i.e., demonstrable process stability and consistency over time. Without stability and consistency over time it is impossible to meaningfully talk about either capability or on-target operation.

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