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EPQ model for imperfect production processes with rework and random preventive machine time for deteriorating items and trended demand

Economic production quantity (EPQ) model is analyzed for trended demand and the units which are subject to constant rate of deterioration. The system allows rework of imperfect units and preventive maintenance time is random. The proposed methodology, a search method used to study the model, is validated by a numerical example. Sensitivity analysis is carried out to determine the critical model parameters. | Yugoslav Journal of Operations Research 25 (2015), Number 3, 425-443 DOI: 10.2298/YJOR130608019S EPQ MODEL FOR IMPERFECT PRODUCTION PROCESSES WITH REWORK AND RANDOM PREVENTIVE MACHINE TIME FOR DETERIORATING ITEMS AND TRENDED DEMAND Nita H. SHAH Department of Mathematics, Gujarat University, India 1 nitahshah@gmail.com Dushyantkumar G. PATEL Department of Mathematics, Govt. Poly.for Girls, India dushyantpatel_1981@yahoo.co.in Digeshkumar B. SHAH Department of Mathematics, L. D. College of Engg., India digeshshah2003@yahoo.co.in Received: July 2013 / Accepted: July 2014 Abstract: Economic production quantity (EPQ) model is analyzed for trended demand and the units which are subject to constant rate of deterioration. The system allows rework of imperfect units and preventive maintenance time is random. The proposed methodology, a search method used to study the model, is validated by a numerical example. Sensitivity analysis is carried out to determine the critical model parameters. It is observed that the rate of change of demand and the deterioration rate have a significant impact on the decision variables and the total cost of an inventory system. The model is highly sensitive to the production and demand rate. Keywords: EPQ, Deterioration, Time-dependent Demand, Rework, Preventive Maintenance, Lost Sales. MSC: 90B05. 1. INTRODUCTION Due to out-of-control of a machine, the produced items do not satisfy the codes set by the manufacturer, but can be recovered for the sale in the market after reprocessing. This 426 N.H.Shah, D.G.Patel, D.B.Shah / EPQ Model For Imperfect Production Proces phenomenon is known as rework, Schrady(1967). At manufacturer‟s end, the rework is advantageous because this will reduce the production cost. Khouja (2000) modeled an optimum procurement and shipment schedule when direct rework is carried out for defective items. Kohet al. (2002) and Dobos and Richter (2004) discussed two optional production models in which either opt to order