IE-OPIM Seminar: Tevhide Altekin
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IE-OPIM Seminar: Tevhide Altekin (Sabancı School of Management)

Remedial actions for disassembly lines with stochastic task times

Date: Wednesday, March 08, 2017
Time: 13:40 – 14:30
Location: FENS G035

Title: Remedial actions for disassembly lines with stochastic task times


Abstract: In lines with stochastic task times, there is a probability that some tasks may not be completed within the given cycle time. In the assembly line balancing literature, remedial actions such as stopping the line, offline repair, and hybrid line have been proposed for such task incompletions. Stopping the line allows the line to be stopped until all incomplete tasks are completed by extending the given cycle time. However, in offline repair, once the given cycle time is elapsed, all the workpieces on the line are moved to the subsequent station. Hence, at the downstream stations tasks with no precedence relation violations due to incomplete tasks are performed and the remaining incomplete tasks are skipped and completed in an offline repair area after the workpiece leaves the line. In a hybrid line both stopping the line and offline repair remedial actions are viable depending on the class of each task: The line is stopped for Finish (F-) tasks and offline assembly is executed for Pass (P-) tasks. Each of these remedial actions have a significant effect on the expected cost due to line stoppages and/or offline repair, which together make up the incompletion costs. Due to the significance of the incompletion costs, balancing stochastic lines requires the incorporation of the remedial action decision as well as quantifying the associated incompletion costs. After reviewing the approaches used in assembly lines for deriving the costs of stopping the line, offline repair and hybrid line remedial actions for a given line balance, we propose the use of these three remedial actions in stochastic disassembly lines. For hybrid disassembly lines, we formulate the problem given the line balance so as to maximize the expected profit as a Mixed Integer Programming model. A full enumeration scheme is proposed to derive the hybrid disassembly line solution. As partial disassembly is allowed, for offline disassembly and hybrid line, we also formulate and solve the task selection problem in order to determine which incomplete P-tasks to execute during offline disassembly. Our computational study aims to show the significance of incompletion costs, analyze the effect of the base cycle time and demonstrate that hybrid lines are capable of improving the expected profit as well as expected cycle time compared to the pure remedial actions. Stopping the line and hybrid line on average yield 26% higher expected profits compared to offline disassembly.


Bio:  Dr. Tevhide Altekin joined Sabancı at School of Management as an Assistant Professor of Operations Management in 2007. She received her B.S., M.S. and Ph.D. degrees in Industrial Engineering from Middle East Technical University. Her research focuses on disassembly line design, assembly line design, production planning, and design of reverse logistics networks. Currently, she is interested in designing after sales logistics networks, socially responsible logistics and solving stochastic assembly/ disassembly line balancing problems. She teaches PhD, MBA and undergraduate level courses in operations management, business process analysis and design, advanced Excel for managers, introduction to management, and business simulation and data analysis.