A new look at the bowl phenomenon

An interesting empirical result in the assembly line literature states that slightly unbalanced assembly lines (in the format of a bowl with central stations less loaded than the external ones) present higher throughputs than perfectly balanced ones. This effect is known as the bowl phenomenon. In this study, we analyze the presence of this phenomenon in assembly lines with integer task times. For this purpose, we modify existing models for the simple assembly line balancing problem and assembly line worker assignment and balancing problem in order to generate configurations exhibiting the desired format. These configurations are implemented in a stochastic simulation model, which is run for a large set of recently introduced instances. The obtained results are analyzed and the findings obtained here indicate, for the first time, the existence of the bowl phenomenon in a large set of configurations (corresponding to the wide range of instances tested) and also the possibility of reproducing such phenomenon in lines with a heterogeneous workforce.