Layer modelling for the inspection allocation problem in re-entrant production systems

Abstract

In the past two decades, re-entrant production systems have received a great deal of attention. One of the most important characteristics of re-entrant production systems is that the work units are manufactured layer-by-layer, so that some defects are more difficult to inspect after they are covered by the next layer. In this research, a mathematical model considering layered fabrication is developed to find the optimal solution for allocating inspections in re-entrant production systems. Workstations of variables data and inspections of quality characteristics measurement are modelled. In addition, this study considers three possibilities for the treatment of detected non-conforming units, namely repair, rework and scrap. Moreover, a heuristic algorithm is proposed in order to improve the optimization method based on complete enumeration, which suffers from a large amount of computation time, especially as the number of workstations increases. The model is highly extensible and applicable, so it can serve as a production-planning tool to solve the inspection allocation problem in re-entrant production systems.

Keywords:

• Inspection allocation problem
• Re-entrant production system
• Layered fabrication
• Workstation of variables data

Acknowledgements

Work was supported in part by the National Science Council of Republic of China under grants NSC 91-2213-E-033-027 and NSC-93-2213-E-033-032.