Reliability optimisation of flexible manufacturing systems with spare tooling

Tool reliability plays an important role in the performance and justificati on of flexible manufacturing systems (FMSs). Failure of a single tool can c ause downtimes over the entire system. This would cause due dates to be mis sed and can result in inferior products. Therefore, in order to justify the large capital investment associated with FMSs, the system must perform in a reliable manner to give an acceptable or required rate of return on the i nvestment. In order to arrive at this objective, FMS reliability must be st udied at the planning and design stages, tool failures pose a major obstacl e to achieving this objective. In this paper, a mathematical model has been developed to determine the spare tooling requirement for the tooling syste m in an FMS, so that a desired system reliability is achieved and the cost is minimised. The influence of tool sharing on cost, reliability, spares re quirement, and tool magazine capacity of the FMS are analysed. The tools an d tool transporter are subject to general failure distributions.