Presented as a paper in IISE annual conference and expo 2021 named "An Integrated Maintenance and Production Planning Optimization Model Considering Downtime Reduction "
Production planning and maintenance planning are often in tactical opposition. In this paper we present an integrated framework and optimization model to find the optimal scheduling of production and maintenance processes and production quantity over a finite planning horizon. The method is intended to be compatible with traditional MRP planning process as well as the increasing use of Industrial IoT (IIoT) and Digital Twin technologies. We assume equipment digital twins are providing us with failure risk assessments over the planning horizon. The model balances conducting or postponing maintenance activities (which control unplanned equipment failure and downtime risks) versus system production capacity reductions due to maintenance activity. We develop a mixed integer optimization model with a goal of concurrently minimizing production and maintenance related costs. The model is built for multiple product and machines, and the production strategy is based on make-to-inventory. Since the effects of time and budget limits are not negligible, we considered the effect of these two in our mathematical model to make it closer to a real-life problem. We provide a numerical study to illustrate the performance of the proposed model, including a sensitivity analysis on model parameters.