Economic design of inspection strategies to monitor dispersion in short production runs

Short-run productions are common in industrial environments where flexibility is required in the manufacturing of parts and several product variants can be produced. Monitoring process stability during the production run is strategic to avoid the occurrence of an excessive number of non conforming units which can lead to excessive scrap or rework costs. The selection of the best control strategy can be obtained with respect to an economic objective by minimizing the cost associated with the implementation strategy. In this paper, several strategies including preventive maintenance, Shewhart, EWMA and CUSUM control charts are compared to monitor process dispersion. Constraints related to the line productivity and the inspection activities configuration have been included in the problem formulation. A proper optimization algorithm has been developed to cope with the investigated problem. A large benchmark of process scenarios has been investigated and the obtained results show that the selection of the best strategy is not a straightforward task due to the influence of several process operating parameters. Finally, a numerical example is detailed to get more insight about the investigated problem.