Thesis. 1976. Ph.D.--Massachusetts Institute of Technology. Dept. of Mechanical Engineering. / Microfiche copy available in Archives and Engineering. / Vita. / Includes bibliographical references. / Ph.D.

This thesis work was carried out at a manufacturing plant in Sweden and they are producing a different kind of components for the company. This thesis work was about an assembly line in the factory where they needed a simulation model in Plant Simulation. The main goal of the thesis work was to break down different losses, building a simulation model and compare it if the results are the same as the real assembly line with similar characteristics. The assembly line consists of several workers and AGVs with three u-shaped lines. Frame of reference describes topics that are related to the project. It consists of theories about simulation, collection of data, the bottleneck of the production line, integrated manufacturing systems and flexible workers. The chapter of literature review presents researches on similar studies, in this case, simulation, bottleneck, and workers in the assembly line. In the chapter Simulation model, there will be an explanation of how data got collected, the transformation of raw data and building a simulation model of it. Also the way the model was programmed and built. Result and analysis, the focus is to analyze the throughput, lead time and work in process parameters to get a steady state graph and confidence interval. This chapter also shows how long time does the model need for warm up and how many replications it needs to be more accurate. Discussion part reviews the whole project and its progress. It covers problems that authors got through, at the same time learning and getting a new experience of tools and methods that were used in this project.

The optimal allocation of buffers in serial production systems is one of the oldest and most researched problems in Industrial Engineering. In general, there are three main approaches to the buffer allocation problem when the objective is to maximize throughput. The first is basically a systematic trial and error procedure supported either by discrete event simulation or analytical models. A second approach is to allocate buffers based on general design rules that have been established in the research literature through experimentation. And the third approach is to apply a buffer allocation optimization algorithm to a specific production line. All these approaches have limitations and could be time and resource consuming. Additionally, most of the existing research on buffer allocation only considers production systems modeled with an infinite supply of raw materials before the first workstation and an unlimited capacity for finished goods after the last workstation. In reality many production systems are designed as closed systems where an interaction between the last and the first workstations in the line is present. In a closed production system, there is a finite buffer after the last workstation and the number of "carriers" holding jobs that move through the line is fixed. The objective of this thesis was to develop efficient heuristic algorithms for the buffer allocation problem in closed production systems. Two heuristics for buffer allocation were implemented. Heuristic H 1 uses the idea that highly utilized workstation stages require any available buffer more than sub-utilized stages. Heuristic H2 uses information stored in the longest path of a network representation of job flow to determine where additional buffers are most beneficial. An experiment was designed to determine if there are any statistically significant differences between throughput values with buffer allocations obtained with a genetic algorithm, also developed in this research, and through puts with buffer allocations generated by Hi and H2. Several types of closed production systems were examined in eight different test cases. No significant differences in performance were observed. The efficiency of the heuristics was also analyzed. A significant difference between the speeds of Hi and H2 is found. The analysis performed in this research indicates that heuristic H2 is sufficiently effective and accurate for determining near optimal buffer allocations in closed production systems. / Graduation date: 2005

Report covers June 1, 1976-July 31, 1978. / Each v. has also a distinctive title. / National Science Foundation. Grant NSF/RANN APR76-12036 National Science Foundation. Grant DAR78-17826

Report covers June 1, 1976-July 31, 1978. / Each v. has also a distinctive title. / National Science Foundation. Grant NSF/RANN APR76-12036 National Science Foundation. Grant DAR78-17826

Report covers June 1, 1976-July 31, 1978. / Each v. has also a distinctive title. / National Science Foundation. Grant NSF/RANN APR76-12036 National Science Foundation. Grant DAR78-17826

Report covers June 1, 1976-July 31, 1978. / Each v. has also a distinctive title. / National Science Foundation. Grant NSF/RANN APR76-12036 National Science Foundation. Grant DAR78-17826

Report covers June 1, 1976-July 31, 1978. / Each v. has also a distinctive title. / National Science Foundation. Grant NSF/RANN APR76-12036 National Science Foundation. Grant DAR78-17826

Report covers June 1, 1976-July 31, 1978. / Each v. has also a distinctive title. / National Science Foundation. Grant NSF/RANN APR76-12036 National Science Foundation. Grant DAR78-17826

Report covers June 1, 1976-July 31, 1978. / Each v. has also a distinctive title. / National Science Foundation. Grant NSF/RANN APR76-12036 National Science Foundation. Grant DAR78-17826