An Integrated Mathematical Model for Selecting the First and Second Layers of Suppliers in a Supply Chain

In recent years, Supplier evaluation and selection, an important element in supply chain management, has been gaining attention in both academic literature and industrial practice. The Mixed integer multi-objective Linear programming model (MIMOLP) presented in this paper aimed to evaluate and select the appropriate set of suppliers considering quantitative and qualitative criteria and in addition to selecting the first layer's suppliers which relate directly to the organization, analyses the characteristics of second-layers suppliers, and design a network to determine the flow rate of products and materials between buyers and best suppliers in both layers. Then allocate the optimum orders to each supplier. Another important feature of this model is considering quantity discounts for the first layer's suppliers and at the same time different kinds of products and raw material can be considered. Finally, the model is solved by using goal programming approach and numerical examples are presented to test the performance of proposed model.