Determining Maintenance Opportunity Window (MOW) in Job-Shop Systems by Considering Manpower of Maintenance

Nowadays, production systems seek to integrate production and maintenance activities. An effective maintenance plan can improve maintenance stability and system performance. Machines that stop for repairing operation impose a high cost on the system. On the other hand, there are always some intangible situations during a production process in which repairing activities can be carried out. If they are detected, system productivity can be improved. The main purpose of this study is specifying Maintenance Opportunity Window (MOW) in job-shop production systems. For this purpose, mathematical models and formulae were developed in order to determine the MOW in a way that they could provide maximum repairing time for the machine and, as a result, the lowest disturbance occurring in production. This model also determines the number of lost products during PM. Considering the manpower of maintenance and M/M/1//k queueing model, the terms required for repairs are addressed. Finally, numerical experiments on and sensitivity analysis of critical parameters of the model, such as the initial level of the buffers and processing rates of the machines, are considered. Model validation is carried out by comparison of the results with a simulation model. In this study, some suggestions for improving the system are proposed.