Integrated Maintenance-Quality policy with rework process under improved imperfect preventive maintenance

We consider a manufacturing system subject to an increasing random failure rate and producing conforming and non-conforming items. Two types of non-defective products are considered: high quality items noted first-rate products and substandard quality items noted second-rate products. Rework activities are proposed for second-rate and non-conforming products in order to improve their quality conditions and sell them at the best price. In order to slow down the degradation process of the manufacturing system and reduce its impact on the quality of output products, a new improved imperfect preventive maintenance (PM) policy with minimal repair at failures is established. It consists in performing a given number of imperfect PM actions before undertaking a perfect one. This study consists in developing an analytical model to determine simultaneously the optimal values of two decision variables: the number of produced batches before performing the imperfect PM, and the number of imperfect PM actions to undertake before applying a perfect one by maximizing the total expected profit taking into account the selling price and production, maintenance and reworking costs. Numerical examples and a sensitivity study are presented to illustrate the use of the proposed model and the obtained results.