Definition and Application of a Process Flexibility Index

Abstract

A performance index, Cf, is developed for assessing the flexibility of candidate engineering designs and manufacturing processes at various stages during product development. The index is a ratio of the range of the feasible space to the range of the specification or measured process variation. The process flexibility index complements the process capability index, Cp, to provide a simple and quantitative basis for practicing the principles of axiomatic design. This quantitative measure can be used to support rational product development and manufacturing investment decisions, and clearly illustrates important concepts regarding controllability across conflicting specifications. A high Cp indicates that the design or process can consistently manufacture the product within precisely defined performance specifications. A high Cf indicates that the process can be easily changed to meet diverse performance specifications. The evaluation of Cf requires the mapping of the global feasible space, the solution to which is also discussed.