A Study of the Effects of Operational Time Variability in Assembly Lines with Linear Walking Workers
Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
In the present fierce global competition, poor responsiveness, low flexibility to meet the uncertainty of demand, and the low efficiency of traditional assembly lines are adequate motives to persuade manufacturers to adopt highly flexible production tools such as cross-trained workers who move along the assembly line while carrying out their planned jobs at different stations . Cross-trained workers can be applied in various models in assembly lines. A novel model which taken into consideration in many industries nowadays is called the linear walking worker assembly line and employs workers who travel along the line and fully assemble the product from beginning to end . However, these flexible assembly lines consistently endure imbalance in their stations which causes a significant loss in the efficiency of the lines. The operational time variability is one of the main sources of this imbalance  and is the focus of this study which investigated the possibility of decreasing the mentioned loss by arranging workers with different variability in a special order in walking worker assembly lines. The problem motivation comes from the literature of unbalanced lines which is focused on bowl phenomenon. Hillier and Boling  indicated that unbalancing a line in a bowl shape could reach the optimal production rate and called it bowl phenomenon.
This study chose a conceptual design proposed by a local automotive company as a case study and a discrete event simulation study as the research method to inspect the questions and hypotheses of this research.
The results showed an improvement of about 2.4% in the throughput due to arranging workers in a specific order, which is significant compared to the fixed line one which had 1 to 2 percent improvement. In addition, analysis of the results concluded that having the most improvement requires grouping all low skill workers together. However, the pattern of imbalance is significantly effective in this improvement concerning validity and magnitude.
Place, publisher, year, edition, pages
2012. , 76 p.
assembly system, discrete event simulation, cross training workers, walking worker assembly line, bowl phenomenon, operational time variability, coefficient of variation imbalance, arrangement of workers
Production Engineering, Human Work Science and Ergonomics
IdentifiersURN: urn:nbn:se:hj:diva-17877OAI: oai:DiVA.org:hj-17877DiVA: diva2:512191
Subject / course
JTH, Production Systems
2012-03-31, 15:30 (English)