Robust design of a cellular-line production system with unreliable facilities

A cellular-line production system consists of multiple flow shops which are individual sets composed of functionally different facilities. The cellular-line production system is carefully designed and controlled so as to group facilities that perform similar operations and balance the workload among facilities considering the planned product mix and its variations. Thus, a drastic reduction in production lead time is possible as long as all of the facilities composing cellular-lines in the system are reliable. The present paper deals with a design problem of the cellular-line production system which includes unreliable facilities. We assume that the times to failure and times to repair are exponentially distributed and that the latter is not lengthy, that is, that the times to repair are at most several times the cycle time, which is the input interval for the cellular lines. A methodology for designing the system in a machine-failure environment is presented and the results of numerical experiments and simulation are shown to verify the usefulness of the proposed methodology. Finally, the practical significance of quantitative analysis and evaluation in the stochastic design problem is discussed.