Modelling the allocation of protective capacity to design unbalanced production lines

This paper highlights the effective design of production capacity as a means to improve productivity of paced lines and ultimately to gain a better competitive position. After a literature review, a model focused on the role of imbalance at the paced line design stage is introduced; then the performances of the model are tested via simulation and results are discussed. Protective capacity is useful to prevent the line productivity from dropping below an unsatisfactory level of return on invested capital even under an environment perturbed by several sources of variance, such as failures, operation time variance and production mix, that increases setups number and time, and ultimately extend task time over the cycle time. While the majority of literature studies treat the design of paced lines with the purpose of balancing, this research shows that a balanced line is both hard to attain and also undesirable, since a source of variance at a given station disrupts the cycle time of the entire line in that the bottleneck dynamically shifts to another station, either upstream or downstream.