Mathematical Modeling and Analysis of Flexible Production Lines

We present a model and analysis of a production line that processes different part types on unreliable machines which operate according to a priority rule. The production line consists of machines separated by storage areas in which parts flow in a fixed sequence. A machine operates on the highest priority part whenever possible, and only operates on lower priority parts when unable to produce the higher priority parts. Part priorities are static and are a function only of part type. The purpose of this thesis is to present mathematical formulations and algorithms for estimating production rates and average inventory levels for each part type in a flexible production line. The qualitative behavior of the multiple-part-type line under different supply and demand scenarios is described. Thesis Supervisor: Stanley B. Gershwin Title: Senior Research Scientist, Department of Mechanical Engineering Acknowledgments I believe that I am one of fortunate people whose professional and personal lives have been benefited by outstanding people. I would like to express my gratitude to all those who gave me the possibility to complete this thesis. My colleagues in the Manufacturing Systems Engineering Community at MIT including Irvin Schick, Baris Tan, and Chiwon Kim, supported me in my research work. I want to thank them all for their help, support, interest, and valuable hints. I want to thank Shinsung ENG, Ltd., Co. for providing me with valuable information and data about the current semiconductor and LCD industries. Mr. Jae Myung Yoo and Dr. Gi-Han Choi in Shinsung ENG shared their knowledge with me in the current issues in industry. Particularly, I am bound to the President Joo-Hun Kim in Shinsung ENG for supporting me throughout my graduate years in various ways. Being a student of Dr. Stanly B. Gershwin, my research thesis advisor, is one of the luckiest things in my life. Stan taught, trained, and directed me toward the world of manufacturing systems. However, our relationship was not limited to the academic interest. We shared our view of nature, life, philosophy, and pretty much everything we could think of. I have been proud of being his student. I also would like to thank his wife, Fran Gershwin, for generously inviting me their summer house in New Hampshire every summer as well as letting be a welcomed guest in her house whenever I needed a temporary accommodation during my graduate years. In shaping and molding my life and personality, there is no one who deserves more credit and thanks than my parents. Their love has sustained me and nourished me. They sacrificed a great deal for me, tolerated my shortcomings. My dad taught me how to be a strong person while my Mom showed me how to be a loving and sharing person. I want to thank my wife, Yujin Lee. She has been more than my wife. Her love has been my inspiration. She has been patiently trusted me all the time. I could not have been completed my study successfully without her inspiration and love. Finally, thank you, God.