本研究將在允許缺貨下，探討不良品重製(Rework)對經濟生產批量的影響。生產系統通常是不完美的，難免會產生部分少數不符合品質標準的產品。不良品的重製或丟棄不僅增加額外的成本，亦會影響整個生產作業的速度和良品存貨的控制。有鑑於此，本研究針對不完美之生產系統，將不良品重製的成本和速度納入制定生產批量的策略中，考慮所生產之不良品於整批生產結束後採用重製的處理方式，使其產品符合品質標準後，再出售給消費者，其不良品比例為一機率密度函數已知的隨機變數。在上述前提下，試建立一個缺貨數量為部分欠撥及部分銷售損失之混合存貨模式，並試以找出最佳生產策略，使其總相關成本最低。 In this study, we investigate the effect of reworking of defective items owing to imperfect processes on the economic production quantities. Some poor-quality products are made because of failure- prone production facility or man-made factors in the production system. When defective items are reworked, there will be no rework cost, but the production rate of the system and the level of the on- hand inventory are also influenced. Therefore, we focus on an imperfect production system and consider the proportion of defective items in the accepted lot is a random variable with known probability distributions. Furthermore, defective items are assumed to be reworked at a constant rate, when production stops. The demand for initial perfect items and the perfect items being reworked is continuous during the inventory cycle. In such conditions, this study develops a mixture inventory model with backorders and lost sales. The objective is to find the optimal strategy in production quantity and in turn minimize the total inventory cost.