Multi-criteria sequencing problem for a mixed-model assembly line in a JIT production system R. Tavakkoli-Moghaddam * , A.R. Rahimi-Vahed Department of Industrial Engineering, Faculty of Engineering, University of Tehran, P.O. Box 11365/4563, Tehran, Iran Abstract Mixed-model assembly lines (MMAL) are a type of production lines where a variety of products models similar to product characteristics are assembled in a just-in-time (JIT) production system. There is a set of criteria on which to judge sequences of product models in terms of the effective utilization of these lines. In this paper, we consider three objectives simultaneously: (i) total utility work cost, (ii) total production rate variation cost, and (iii) total setup cost. In this study, these three objectives are first weighted by their relative importance weights and then a new mathematical model is pre- sented. To solve this model, a memetic algorithm (MA) is proposed to determine suitable sequences. The performance of the MA is compared with the Lingo 6 software. A number of test problems are carried out to verify the good ability of the proposed MA in terms of the solution quality and computational time. The computational results reveal that the MA finds promising results, especially in the case of large-sized problems. Ó 2006 Elsevier Inc. All rights reserved. Keywords: Multi-criteria sequencing; Mixed-model assembly line; JIT system; Memetic algorithm 1. Introduction Mixed-model assembly lines are a type of production lines that are capable of the diversified small lot pro- duction and are able to respond promptly to sudden demand changes for a variety of models without holding large inventories. The effective utilization of a mixed-model assembly line requires solving two problems in the sequential manner: (1) design and balance the line and (2) determine the production sequence for different models. In this paper, we assume that the line has already been balanced and a sequencing problem is only considered. The sequence of introducing models to the mixed-model assembly line should be determined considering the main goals which are crucial to efficiently implement a just-in-time (JIT) production system. Numerous research efforts have been directed towards the development of computer approximation algorithms or heuristics as well as their subsequent implementation to solve mixed-model assembly lines. Monden [1] defines 0096-3003/$ - see front matter Ó 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.amc.2006.02.033 * Corresponding author. E-mail address: tavakoli@ut.ac.ir (R. Tavakkoli-Moghaddam). Applied Mathematics and Computation 181 (2006) 1471–1481 www.elsevier.com/locate/amc