A DYNAMIC TOOL REQUIREMENT PLANNING-MODEL FOR FLEXIBLE MANUFACTURING SYSTEMS

Despite their strategic potential, tool management issues in flexible manufacturing systems (FMSs) have received little attention in the lit erature. Nonavailability of tools in FMSs cuts at the very root of the strategic goals for which such systems are designed. Specifically, th e capability of FMSs to economically produce customized products (flex ibility of scope) in varying batch sizes (flexibility of volume) and d elivering them on an accelerated schedule (market response time) is se riously hampered when required tools are not available at the time nee ded, On the other hand, excess inventory of tools in such systems repr esents a significant cost due to the expensive nature of FMS tool inve ntory. This article constructs a dynamic tool requirement planning (DT RP) model for an FMS tool planning operation that allows dynamic deter mination of the optimal tool replenishments at the beginning of each a rbitrary, managerially convenient, discrete time period. The analysis presented in the article consists of two distinct phases: In the first phase, tool demand distributions are obtained using information from manufacturing production plans (such as master production schedule (MP S) and material requirement plans (MRP)) and general tool life distrib utions fitted on actual rime-to-failure data. Significant computationa l reductions are obtained if the tool failure data follow a Weibull or Gamma distribution. Tn the second phase, results from classical dynam ic inventory models are modified to obtain optimal tool replenishment policies that permit compliance with such FMS-specific constraints as limited tool storage capacity and part/tool service levels. An impleme ntation plan is included.