| dc.description.abstract | In spite of the implementation of modern technology and an efficient control procedure to improve equipment, the deterioration of the production process is unavoidable in most manufacturing industries. Inspections and maintenance activities are performed in virtually every production system. In this study, we construct models that allow us to economically determine the optimal inspection/disposition strategy for a batch of items produced by a machine that is subject to random breakdowns. We use the proposed mathematical framework to explore the issues relating to inspection errors, rework, preventive maintenance level, and minimal repair. The operational implications of the optimal strategy are then analyzed with a selected set of numerical results.
We formulate dynamic programming of optimal strategy for two types of inspection activities: inspection of products and inspection of production systems. For inspection of products, we develop models of off-line inspection for a deterioration process having general shift distribution with an increasing hazard rate. To have an off-line inspection following an unreliable process is an appropriate quality assurance tactic in certain systems. Previous work has dealt exclusively with finding the point where the process shifts away from its in-control state to an out-of-control state. Our models incorporate the economic aspects of the inspection activity and of the two types of product inspection errors. Ignoring the true economics of quality assurance can result in unnecessary costs and time delays. We determine the first unit inspected and the average number to be inspected in a batch. We also study the effect of allowing rework on the optimal inspection strategy.
For inspection of production systems, we generalize the classical economic production quantity model to consider possibilities of preventive maintenance errors and minimal repair. Our model solves simultaneously the optimal number of inspections, the duration of the first inspection interval, the economic production quantity, and the preventive maintenance level.
Despite the strong interdependence between production, quality and maintenance, these three main aspects of any manufacturing system are traditionally modeled as separate problems. Few attempts have been made to integrate them in a single model that captures their underlying relationships. Our study essentially explores models for the joint optimization of production quantity, quality assurance inspections, and maintenance level. Our results demonstrate that these different but interrelated aspects of a manufacturing system can be captured rigorously in a united framework. Numerical simulations also illustrate the importance of viewing all theses decisions concerning core manufacturing processes in an integrated manner, rather than as a set of separate decisions. | en_US |