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Unpaced production lines with three simultaneous imbalance sources

Tom McNamara (Department of Finance and Operations, ESC Rennes School of Business, Rennes, France)
Sabry Shaaban (Department of Economics, Strategy and Organization, Groupe ESC La Rochelle – Cerege, La Rochelle, France)
Sarah Hudson (Department of Finance and Operations, ESC Rennes School of Business, Rennes, France)

Industrial Management & Data Systems

ISSN: 0263-5577

Article publication date: 27 September 2011




The purpose of this paper is to investigate the performance of unpaced reliable production lines that are unbalanced in terms of their mean operation times, coefficients of variation and buffer capacities.


Simulations were carried out for five‐ and eight‐station lines with various buffer capacities and degrees of means imbalance. Throughput, idle time and average buffer level performance indicators were generated and statistically analysed.


The results show that an inverted bowl allocation of mean service times, combined with a bowl configuration for coefficients of variation and a decreasing order of buffer sizes results in higher throughput and lower idle times than a balanced line counterpart. In addition, considerable reductions in average inventory levels were consistently obtained when utilizing a configuration of progressively faster stations, coupled with a bowl‐shaped pattern for coefficients of variation and an ascending buffer size order.

Research limitations/implications

The results for these specific experiments imply that resources expended on trying to achieve a balanced line could be better used by seizing upon possible enhanced performance via controlled mean time, variability and buffer imbalance. Results are valid for only the line type and parameter values used (simulation results are specific and not general).

Practical implications

Guidelines are provided on design strategies for allocating labour and capital unevenly in unpaced lines for better performance in terms of increased throughput or lowered idle time or average buffer levels.


This paper might be viewed as one of the first simulation investigations into the performance of unpaced production lines with three sources of imbalance.



McNamara, T., Shaaban, S. and Hudson, S. (2011), "Unpaced production lines with three simultaneous imbalance sources", Industrial Management & Data Systems, Vol. 111 No. 9, pp. 1356-1380.



Emerald Group Publishing Limited

Copyright © 2011, Emerald Group Publishing Limited

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