Sequencing just-in-time mixed-model assembly lines under station-load and part-usage constraints

This paper deals with two most important problems, from both practical and theoretical standpoints, arising in sequencing mixed-model assembly lines. Such lines have become core components of modern repetitive manufacturing, and just-in-time (JIT) manufacturing in particular. One problem is to keep the usage rate of all parts fed into the final assembly as constant as possible (the ‘level-scheduling problem’), while the other is to keep the line's workstation loads as constant as possible (the ‘car-sequencing problem’). In this paper the combined problem is formulated as a single-integer programming model. The LP-relaxation of this model is solved by column-generation techniques. The results of an experimental evaluation show that the lower bounds are tight.