The preliminary design or reconfiguration of modular manufacturing lines is addressed. The modules are multi-spindle units. Each unit executes a subset of operations. The set of all available spindle units and their costs are known. The problem is to select the right spindle units and to arrange them into linear workstations. The objective is to design such a line respecting technological constraints and minimizing the investment cost. In this paper, some efficient formulations of linear integer programming (IP) models and specific techniques to reduce the calculation time are proposed. Experiments were carried out which highlight the performance of the models.