How to improve competitive edges to meet rapidly changing technological innovations and dynamic customer needs is crucial for the survival and success of firms under a global competitive market. Many firms realize that a good supply chain management is a necessity in the intensive competitive international market. In consequence, it is important for a firm to provide products with a lower cost and good quality at the right time and place to maintain a competitive edge. In this paper, a joint replenishment model for multiple suppliers is developed using a mixed integer programming (MIP) to determine the optimal replenishment time and quantity. The model aims to solve the shortcomings of existing joint replenishment models and to increase the performance and customer satisfaction of the replenishment system. The proposed model is applied in a solar cell manufacturer to maintain a good integrated purchase and production plan.