Machine repairing models for production systems

In this paper we consider manufacturing systems of rn identical unreliable machines producing one type of product. The operating time of each machine is exponentially distributed. The repairing process of a machine requires m ore than one phase. In each phase, the repair time is exponentially distrib uted and more than one operator may be required for fixing a broken machine . Here we consider two models of manufacturing systems. In the first model, there are r operators assigned in one server to repair a broken machine. T he repairing rate in each phase depends on the number of operators there. T his is a generalized model discussed in Buzacott and Shanthikumar [11]. We then consider a two-phase repairing model. Two groups of operators are assi gned in the two phases. Each operator can handle one broken machine in each phase individually. This model is a generalization of Eben-Chaime's model [8]. Average profits are derived for both models and can be optimized by su itable allocation of the number of machines and operators in the systems. ( C) 2001 Elsevier Science B.V. All rights reserved.