Integrated production, quality and maintenance models for multistage production-inventory systems.

Abstract

Multi-stage production-inventory systems (MS-PIS) are very common in any manufacturing environment. The research in this area is really challenging both from modelling and application point of view. Production, quality and maintenance are three important and interrelated functions in any industrial process. These aspects are traditionally treated as three separate problems even for single stage production systems which is likely to render sub-optimal solutions. Here we give an overall review of research literature dealing with lot sizing decisions in series MS-PIS with its deficiencies and limitations to facilitate the scope of future research and applications. We formulate various mathematical models so as to integrate quality and maintenance with the lot sizing decisions for series MS-PIS. Both uniform lot sizing and variable lot sizing models are considered. In the case of imperfect production processes, the screening of defective items between stages and errors in screening inspections are also considered. In uniform lot sizing model, the effect of maintenance-inspection and process restorations is taken into account. A fractional factorial experiment is designed and analysed to check the sensitivity of various response variable against various system parameters. While, in the case of variable lot sizing model, the effect of preventive maintenance is also considered beside process restorations. Mathematical models are coded in 'C' for comparison purposes. Several numerical examples are used to demonstrate the usefulness of the developed models.