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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.ejor.2008.03.037 Byline: V. Boschian (a), N. Rezg (a), A. Chelbi (b) Keywords: Simulation; Preventive maintenance; Availability; Multi-criteria analysis Abstract: This paper compares two strategies for operating a production system composed of two machines working in parallel and a downstream inventory supplying an assembly line. The two machines, which are prone to random failures, undergo preventive and corrective maintenance operations. These operations with a random duration make the machines unavailable. Moreover, during regular subcontracting operations, one of these machines becomes unavailable to supply the downstream inventory. In the first strategy it is assumed that the periodicity of preventive maintenance operations and the production rate of each machine are independent. The second strategy suggests an interaction between the periods of unavailability and the production rates of the two machines in order to minimize production losses during these periods. A simulation model for each strategy is developed so as to be able to compare them and to simultaneously determine the timing of preventive maintenance on each machine considering the total average cost per time unit as the performance criterion. The second strategy is then considered, and a multi-criteria analysis is adopted to reach the best cost-availability compromise. Author Affiliation: (a) SdP/LGIPM, Ile du Saulcy, F-57045 Metz-Cedex, France (b) Ecole Superieure des Sciences et Techniques de Tunis, Tunisia

This paper deals with imperfect preventive maintenance (PM) optimisation problem. The system to be maintained is typically a production system assumed to be continuously monitored and subject to stochastic degradation. To assess such degradation, the proposed maintenance model takes into account both corrective maintenance (CM) and PM. The system undergoes PM whenever its reliability reaches an appropriate value, while CM is performed at system failure. After a given number of maintenance actions, the system is preventively replaced by a new one. Both CM as well as PM are considered imperfect, i.e. they bring the system to an operating state which lies between two extreme states, namely the as bad as old state and as good as new state. The imperfect effect of CM and PM is modelled on the basis of the hybrid hazard rate model. The objective of the proposed PM optimisation model consists on finding the optimal reliability threshold together with the optimal number of PM actions to maximise the average availability of the system. A mathematical model is then proposed. To solve this problem an algorithm is provided. A numerical example is presented to illustrate the proposed maintenance optimisation model. [ABSTRACT FROM AUTHOR]

This study deals with the problem of dependence between production and failure rates in the context of a multi-product manufacturing system. It provides an answer about how to produce (i.e. the production rates) and what to produce (i.e. which product) over a finite horizon of H periods of equal length. We consider a single randomly failing and repairable manufacturing system producing two products Pa and Pb. The product Pa is produced to supply the strategic demand d(k) of the principal customer via a buffer stock S over k periods (k = 1, 2, ... , H). The second product Pb is produced to meet a secondary but very profitable demand. It is produced during a given interval at the end of each period k. We develop a genetic algorithm to determine simultaneously the optimal production rate of the first product during each period k and the optimal duration of the production interval of the second product, maximising the total expected profit. [ABSTRACT FROM AUTHOR]

Multi-state systems (MSS) are systems whose stochastic degradation process is characterised by several performance levels varying from nominal functioning to complete failure. MSS arise naturally in many application areas. MSS reliability evaluation and estimation has received much attention from researchers and a wide range of papers dealing with MSS have been published. In this paper, an approach based on Kronecker algebra combined with stochastic processes is proposed to evaluate the reliability of a series–parallel MSS. The main advantage of the proposed approach is that the mathematical expressions of the MSS reliability indices are derived from data of individual elementary components without generating the whole, possibly huge, MSS state space. Furthermore, the approach is well formalised and easy to implement thanks to Kronecker algebra operators. Examples are given to illustrate the proposed approach. [ABSTRACT FROM PUBLISHER]

Nowadays companies have to consider the impact of their production systems on the environment. This paper presents a condition-based maintenance policy for a production system under environmental constraints. The studied system is subject to random failures that can cause production losses and have a negative influence on the environment. Such failures cause the release of a refrigerant gas that induces a heavy penalty cost from a given threshold level. A mathematical model is developed in order to reduce environmental degradation where the average cycle cost per time unit is considered as the objective function. A numerical example and a sensitivity study are given to illustrate the proposed model. [ABSTRACT FROM PUBLISHER]

This article, inspired by an industrial problem, develops efficient maintenance and just-in-time production policies in a subcontracting environment according to two orientations. The first invokes subcontracting with the objective of satisfying a constant customer demand knowing that our production system, composed of a machine M1, cannot satisfy the totality of demand. Subcontracting is represented by a machine M2 which has a constant failure rate, while three maintenance policies for M1 are tested and evaluated. The second orientation takes the perspective of our production system as a supplier which is obliged to allocate part of its production capacity to subcontracting so as to satisfy a constant demand. We consider a production system made up of two machines, both of which produce a single type of product, are subject to breakdowns and can carry out subcontracting tasks. The objective of this part of the article is to prove the efficiency of the so-called integrated maintenance policy, which combines production and maintenance decisions in a subcontracting environment. [ABSTRACT FROM AUTHOR]

In this paper, we develop a joint quality control and preventive maintenance policy for a randomly failing production system producing conforming and non-conforming units. The considered system consists of one machine designed to fulfil a constant demand. According to the proportion l of non-conforming units observed on each lot and compared to a threshold value lm, one decides to undertake or not maintenance actions on the system. In order to palliate perturbations caused by the stopping of the machine to undergo preventive maintenance or an overhaul, a buffer stock h is built up to ensure the continuous supply of the subsequent production line. A mathematical model is developed and combined with simulation in order to determine simultaneously the optimal rate, [image omitted] and the optimal size h* which minimize the expected total cost per time unit including the average costs related to maintenance, quality and inventory. [ABSTRACT FROM AUTHOR]

In this paper, we deal with the problem of joint maintenance and production management under a subcontracting constraint. We will study a system with a machine M which undergoes corrective maintenance actions together with preventive maintenance actions, both of which have random durations. A stock S with a capacity h is developed at a rate α = Umax - d, where Umax = production rate, d = constant demand, and Umax > d. In addition, machine M is allocated to carry out subcontracting tasks (ST) at a frequency A1, for an effective duration A2, during which time it cannot be used to fulfil our system's demand d. We initially study the system analytically when the machine M is forced to carry out a single subcontracting task during each cycle T. We thereafter present a generalization of the subcontracting constraint which entails assigning the machine M to subcontracting several times during each cycle. [ABSTRACT FROM AUTHOR]

This paper investigates an integrated strategy of inventory control and preventive maintenance for a randomly failing production unit subject to a minimum required availability level. The production unit is submitted to a maintenance action as soon as it reaches a certain age m or at failure, whichever occurs first. A buffer stock h is built up at time A from the start of a production cycle in order to allow a continuous supply of the subsequent production unit at a constant rate during repair and preventive maintenance actions whose respective durations are random. A mathematical model and a numerical procedure are developed to find simultaneously the optimal values of the three decision variables (m*, h*, A*) which minimize the total average cost per time unit and satisfy the availability constraint. [ABSTRACT FROM AUTHOR]

The paper describes a new preventive maintenance approach for manufacturing systems under environment constraints. The manufacturing system under consideration consists of a machine M1 that produces a single product in a Just-in-Time context. To satisfy a constant demand d, the system called upon another machine M2 (the subcontractor), comprising the so-called environment, which produces at a certain rate the same type of product as M1. Both machines are subjected to random failures. Whereas machine M2 is uncontrollable from the maintenance point of view, an age-limit policy is used for preventive maintenance of machine M1. It is proved that the best age to perform preventive maintenance depends on the history of machine M1 and the state of M2. A numerical example is used to illustrate the proposed approach. [ABSTRACT FROM AUTHOR]

A marked graph-based control synthesis method is proposed for discrete event systems. The proposed approach solves the forbidden state problems characterized by a set of General Mutual Exclusion Constraints (GMEC) and takes into account unobservable transitions. It exploits the structural dependence of places involved in GMEC constraints. For each case, analytical expression of the GMEC in its worst case, in terms of reachable marking, is given according to the observable firing sequence of the system. These constraints are then evaluated on-line by the supervisor. The proposed approach is illustrated on a real example. [ABSTRACT FROM AUTHOR]

This paper proposes an integrated method for preventive maintenance and inventory control of a production line, composed of n machines (n ≥ 1) without intermediate buffers. The machines are subject to failures and an age-dependent preventive maintenance policy is used. Approximate analytical results are proposed for the one machine case. Simulation software is used to model and simulate the behaviour of the production line of n machines under various maintenance and inventory control strategies. A methodology combining the simulation and genetic algorithms is proposed jointly to optimize maintenance and inventory control policies. Results are compared with the analytical solutions. [ABSTRACT FROM AUTHOR]