Kazmer, David O, Deepak Kapoor, Christoph Roser, Liang Zhu, David Hatch, and Yanli Zhao. “Definition and Application of a Process Flexibility Index.” ASME Journal of Manufacturing Science and Engineering 125 (2003): 164–72.
A performance metric is developed for assessing the flexibility of candidate engineering designs and manufacturing processes at various stages during product development. The index is a weighted ratio that compares the likelihood of a manufacturing process to significantly alter the product quality attributes relative to the defined specifications. The process flexibility index, Cf, complements the process capability index, Cp to provide a simple and quantitative basis for assessing the agility and consistency of manufacturing processes in delivering quality product. The process flexibility index is a quantitative measure that can be used to support rational product development and manufacturing investment decisions, and clearly illustrates important concepts regarding controllability among conflicting specifications. A high Cp indicates that the 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.