The Integrated Research On Delay-time-based Maintenance And Production Plan

In modern companies, maintenance schedule and production plan are two important activities. The maintenance department has to ensure the proper functioning of the system through maintenance actions, whereas the production department has to make production palnning to satisfy production demands. Conflict is inevitably generated since the two departments share the same system. Some negative effects may happen if the arrangement is not appropriate, such as the reduction of system life and production delays. Researches are always separated based on the two activities, and there are only a few studies on the integrated area with some gaps needed to be filled. This paper proposes the integrated maintenance and production model based on the delay-time concept, below are the main content and innovation points:1) An integrated economic production quantity and maintenance problem is studied. Different from previous works which are restricted to the one-product case in the integrated area, this paper considers the problem of jointly determining the economic production quantity and preventive maintenance policy for a production system that can produce multiple products alternately, and construct the integrated model of expected profit per unit time. Based on reality, some setup times are selelcted as the preventive maintenance window, the optimal preventive maintenance sequence and the optimal lot sizes can be calculated by maximizing the integrated model.2) To further research the integrated economic production quantity and maintenance problem, the downtimes caused by maintenance and setup are considered in the model. The expected number of failures and defects are calculated more accurate by the actual running time of the system. In practice, the function of system is declining with the incremental system running time, so some unqualified products may be produced. Considering the downtime and unqualified products in the integrated model of expected profit per unit time, the optimal preventive maintenance sequence and the optimal lot sizes can be also obtained.3) Integrating maintenance and medium-term tactical production planning in a multi-product production system, the tactical production planning problem is different from the economic production quantity problem. At the tactical production planning level, considering the finite production planning horizon, which includes severel equal-length periods, the demands in every period are given. The preventive maintenance is carried out at the end of some periods, the model of the production capacity is constructed, unqualified product is also considered in the model. The objective is to minimize the sum of maintenance, production, inventory, backorder cost and the cost of unqualified products within the planning horizon.4) Considering sequence-dependent setup problem in the integrated maintenance and medium-term tactical production planning model. There are two types of setup structures, usually, production changeover between different products can incur setup time and setup costs, if the setup time and cost in a period are independent of the sequence, it is termed as a sequence-independent structure. Alternatively, the sequence-dependent structure refers to the case where the setup time and costs depend on the sequence of the products. This paper constructs the integrated maintenance, production and sequence-dependent setup structure model, and calculates the optimal preventive maintenance interval and the production quantity in every periods, and gets the optimal setup sequence based on some constrains.