Reliability Optimisation of FMS with Spare Tooling

Tool reliability plays an important role in the performance and justification of flexible manufacturing systems (FMS). Failure of a single tool can cause downtimes over the entire system. This results in missing due dates, and inferior products. Therefore, in order to justify the large capital investment associated with FMS, the system must perform in a reliable manner to give an acceptable or expected rate of return on capital. FMS reliability should be studied at the planning and design stages, as tool failures pose a major obstacle to achieving this objective. In this paper, a mathematical model has been developed to determine the spares requirement of the tooling system in an FMS, so that the desired system reliability is achieved and the cost is minimised. The influence of tool sharing on cost, reliability, spares requirement, and tool magazine capacity of the FMS are analysed. The tools and tool transporter are subject to general failure distributions.