In this paper, the balancing problem of assembly lines with skilled and unskilled workers while there the possibility of installing multi-manned workstations is addressed. In such a system, the skilled workers are hired permanently while the unskilled ones can be hired temporarily in order to meet the seasonal demands. A mixed integer programming formulation is presented to solve this problem. The objective is to minimize the number of temporary workers as the first objective and the number of workstations as the second one. The proposed formulation has been used to solve some experimental instance found in the literature. The results validate the effectiveness of installing multi-manned workstations in comparison to single-manned ones proposed in literature.
