In today's competitive market, time and cost are two essential factors that manufacturers should take into consideration in their supply chain management. Therefore, the selection of appropriate length of each time period is critical to ensure competitive delivery time. In this paper, a mathematical model for defective products supply chain that determines the most appropriate length of each period is proposed. In addition the model also optimizes costs and Economic Production Quantity (EPQ). In this model, defective goods are repairable and some of them are considered as scrap and after reworking the scrap goods are sold at a low price.