Equilibria, stability, and transients in re-entrant lines under FBFS and LBFS dispatch and constant release

A model of a re-entrant line, consisting of the bottleneck workcenter and time delays representing other workcenters, is considered. Its mathematical description is provided and performance metrics are introduced. The steady states of this model and their stability properties are investigated under two dispatch policies-first buffer first served (FBFS) and last buffer first served (LBFS)-and under constant release rate. The transients due to machine downtime are also analyzed. It is shown that, although LBFS may be viewed as having superior steady-state characteristics, it induces longer and more volatile transients than FBFS and, in some cases, periodic and chaotic regimes.