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چكيده انگليسي :

Simultaneous lot sizing and scheduling in small foundries Reza Jafari re jafari@in iut ac ir Date of Submission 2014 11 12 Department of Industrial and Systems Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language PersianSupervisor Mehdi Bijari bijari@cc iut ac irAbstract After steel industry and oil industry casting industry is one of the most important industries Casting parts trading is a large market and it has large amount in international trade A suitableproduction planning is an important problem in the foundries Production planning helps to goodoperations like appropriate response to the needs of customers reduce the production costs in thefoundries In this dissertation simultaneous lot sizing and scheduling in small foundries is studied The properties of small foundries include only one furnace is usually operating at any point intime the preparation of sand molds is a manual process slight use of automation and the existenceof finishing step for correction of casting parts In recent decade one of the significant visions ismajor increase in level of customer service in Just In Time JIT in make to order systems According to this vision reducing the cost of delay orders and holding products as one of the goalsof this dissertation is considered In this study according to the existing constraints in theproduction system of small foundries a mathematical model for the simultaneous lot sizing andscheduling in small foundries on the basis of GLSP is developed The objective function of thismodel is minimizing the total costs of preparing the furnace work in process and final productholding and delay orders Features of this model include decision making about the entire processof production simultaneously considering constraints on production system and coordinatingbetween molding and pouring steps So far in the literature production planning in foundries withall of mentioned features has not yet been considered Since this is a NP Hard problem so themathematical model cannot solve large size problems Two heuristic algorithms based on fixingand optimizing and a heuristic algorithm based on rolling horizon are developed to solve the largescale problems These algorithms are evaluated by solving 120 instances The average time to solvethese problems in the algorithm based on rolling horizon is 40 22 seconds and in the first andsecond algorithms based on fixing and optimizing is 62 13 and 48 18 respectively Computationalresults show while these algorithms reduce solution time significantly the solutions quality issuitable In terms of the solution quality the average distance the solutions obtained by thealgorithm based on rolling horizon and the first and second algorithms based on fixing andoptimizing from solution obtained by implementation of the proposed mathematical model in theduration 7200 seconds is 4 47 2 52 and 2 73 in percentage respectively So in terms of solutiontime the algorithm based on rolling horizon and in terms of the solution quality the first algorithmbased on fixing and optimizing have a better performance Key words small foundry lot sizing scheduling due date holding cost

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تعيين همزمان اندازه ي دسته و زمان بندي توليد در ريخته گري هاي كوچك

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