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 desiredformat. 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 witha heterogeneous workforce.

In this paper, a general scheme for generating extra cuts during the execution of a Benders decomposition algorithm is presented. These cuts are based on feasible and infeasible master problem solutions generated by means of a heuristic. This article includes general guidelines and a case study with a fixed charge network design problem. Computational tests with instances of this problem show the efficiency of the strategy. The most important aspect of the proposed ideas is their generality, which allows them to be used in virtually any Benders decomposition implementation.