Analysis of a conveyor queue in a flexible manufacturing system.

In a flexible manufacturing system, stations are arranged along a common conveyor that brings items for processing to the stations and also carries away the processed items. At each station, specialized robots automatically load and unload items on and off the conveyor. We examine here a single station in such a system. A new kind of queueing problem arises, with input- output dependencies that result because the same conveyor transports items both to and from the station. The paper analyzes two models of a station. Model 1 has one robot that cannot return a processed item to the conveyor while unloading a new item for processing. Model 2 has two robots to allow simultaneous loading and unloading of the conveyor. A principal goal of the analysis is the proper choice of the distance separating the two points at which items leave and rejoin the conveyor.