Supply chain models for an assembly system with preprocessing of raw materials

ii ACKNOWLEDGEMENTS I would like to express my gratitude to Dr. Bhaba R. Sarker for his guidance and support throughout this work. It has been a very rewarding experience working with him. His insights into issues other than the thesis have also been very useful. I would also like to thank Dr. Dennis Webster for providing valuable advice. His comments and suggestions have certainly improved the quality of this work. I would like to thank him, Dr. Lawrence Mann, Jr. for assisting and serving on my committee. Finally, special thanks to my parents, teachers, religious teachers, friends for their constant encouragement and best wishes. I also would like to thank my wife Asheka for her constant help and encouragement and who made my stay in USA a pleasant one. Figure 5.8. Effect of setup (order and production) cost on total cost … … … 68 Figure 6.1. A single cycle schedule of SSSCS of (Example 3.1) … … … … 71 Figure A.1. Work-in-process inventory build-up at processing stage … … … 84 Figure B.1: Assembly product inventory build-up … … … … … … … 87 vii ABSTRACT An assembly line that procures raw materials from outside suppliers and processes the materials into finished products is considered in this research. An ordering policy is proposed for raw materials to meet the requirement of a production facility, which, in turn, must deliver finish products i n a fixed quantity at a fixed time interval to the outside buyers. Two different types of raw materials, 'unfinished' and 'ready-to-use', are procured for the manufacturing system. The 'unfinished raw materials' are turned into 'processed raw materials' after preprocessing. In the assembly line, the 'processed raw materials' and the 'ready raw materials' are assembled to convert into the final products. A cost model is developed to aggregate the total costs of raw materials, Work-in-process, and finished goods inventory. Based on the product design and manufacturing requirement a relationship is established between the raw materials and the finished products at different stages of production. A non-linear integer-programming model is developed to determine the optimal ordering policies for procurement of raw materials, and shipment of assembly product, which ultimately minimize the total costs of the model. Numerical examples are presented to demonstrate the solution technique. Sensitivity analysis is performed to show the effects of the parameters on the total cost model. Future research direction is suggested …