A multi-period analysis to minimize the total number of operators in labor-intensive production lines

Cellular Manufacturing (CM) is widely recognized as one of the most popular production lines. In the context of labor-intensive cells, hierarchical phases have been adopted in many previous papers, despite its shortcomings. However, integrating the hierarchical phases is difficult because the problem is non-linear. This paper proposes a new model without phases and compares it with the hierarchical model. Firstly, the integrated model based on hierarchical phases is redefined using two new decision variables. The first considers products, operations, cells and operators simultaneously, while the second uses cycle time instead of production rate. Secondly, the proposed model is solved by linearizing the non-linear equation that multiplies continuous and binary variables. Through numerical experiments, we demonstrate instances where the proposed model results in fewer operators than the hierarchical model. The proposed model has also the potentials to be extended to production lines with both “cobots” and operators.