In this article, we present an acceptance sampling plan for machine replacement problem based on the backward dynamic programming model. Discount dynamic programming is used to solve a two-state machine replacement problem. We plan to design a model for maintenance by consid-ering the quality of the item produced. The purpose of the proposed model is to determine the optimal threshold policy for maintenance in a finite time horizon. We create a decision tree based on a sequential sampling including renew, repair and do nothing and wish to achieve an optimal threshold for making decisions including renew, repair and continue the production in order to minimize the expected cost. Results show that the optimal policy is sensitive to the data, for the probability of defective machines and parameters defined in the model. This can be clearly demonstrated by a sensitivity analysis technique.
Just in time (JIT) philosophy has grown to a new high level since its evolution and has successfully been implemented in manufacturing. As it is universally accepted that manufacturing and maintenance cannot be managed as a separate function, the aim of the present study is to evaluate various elements of JIT to implement in maintenance sector which have high degree of importance in Global context. It is because now maintenance also plays an important role in optimization of business processes. Maintenance operations are much like manufacturing operations where both employ processes that add value to the basic input used to create the end products. JIT focuses on the processes, not the product. It can, therefore, be applied to any process in manufacturing or maintenance operations. For this, literature related to JIT usage and performance is reviewed. Thirty-eight elements are analyzed from sixty-five research papers of global context. With aid of theoretical analysis and brain storming with maintenance specialists of JIT elements who have implemented it for manufacturing industries, eighteen elements are selected to check the implementation of JIT philosophy in maintenance sector. Relative importance of such elements are also highlighted in the article.
This paper presents an empirical investigation to rank different factors influencing on maintenance strategies on Iranian oil terminals’ company. The study determines four main factors, production quality, reliability, cost and safety. Using fuzzy analytical process, the study determines various factors associated with each main factor and ranks them by performing pair-wise comparisons. The results indicate that reliability ranks first (0.255), followed by production quality (0.252), cost (0.25) and safety (0.244). In terms of reliability, the best utilization of resources is number one priority followed by increase access to maintenance tools, reduction in production interruption are among the most important issues. In terms of production quality, reduction in system failure as well as reworks is the most important factors followed by customer satisfaction and defects. In terms of cost items, ease of access to accessories and consulting are important factors followed by necessary software, hardware and training programs. Finally, in terms of safety factors, external, internal and employee services are the most important issues, which are needed to be considered.
It is necessary for companies and industries to select the most appropriate maintenance strategy to increase the reliability and safety level with reasonable cost. The primary objective of this paper is to assess different maintenance strategies and to select the best and the most appropriate alternatives for Saipa vehicle industry in Tehran, Iran. For this purpose, we simultaneously consider numerous conflicting objectives and constraints. In this study to counter with this conflicting and to consider the dependency among the qualitative and quantitative criteria and sub-criteria, an integration of Analytic Network Process (ANP) and fuzzy set theory are considered. Therefore, factors playing important role in selecting the best maintenance strategy are determined by reviewing the research literature and interviewing with the experts by Delphi technique. Considering the relations among different factors, a network with 4 criteria and 28 sub-criteria are proposed. In the next step, ANP technique is applied for ranking effective factors in evolution of appropriate maintenance strategy. Results reveal that the best maintenance strategy for fixture body of pride (setter) is corrective maintenance.
This paper deals with a single-machine scheduling problem with maintenance activities. Our purpose is to provide a near optimal solution using metaheuristics approach. In this problem, there are n jobs and m machines (m?n), each job must be assigned to one and only one machine, where the processing time of job (j) is (p_j). Furthermore there are M_G groups where each group has a fix periodic interval T and for each group, the maximum number of jobs processed in the machines available time interval (T) is K, (M_G=m/K). For finding the near optimal solution, we consider optimizing total cost scheduling problem. This problem has two types of costs, group cost and gap cost. In this study, first, proposed problem is formulated in a mathematical model. Next, a heuristic genetic algorithm is used to obtain the proposed problem and on example is presented to verify the efficiency of the algorithm.