OPTIMIZATION OF INVENTORY SYSTEM WITH DEFECTS, REWORK FAILURE AND TWO TYPES OF ERRORS UNDER CRISP AND FUZZY APPROACH

In this paper, a new approach was applied to a single-item single-source (SISS) system at the "EOQ - type" mode considering imperfect items and uncertainty environment. The mentioned method was intended to produce an optimum order/pro duction quantity as well as taking care of imperfect pro-cesses. The imperfect proportion of the received lot size was described by an imperfect inspection process. That is, two-way inspection errors may be com-mitted by the inspector as separate items. Thus, this survey was aimed to maximize the benefit in the traditional inventory systems. The incorporation of both defects and defective classifications (Type-I&II errors) was illustrated, in a way that the defects were returned by the consumers. Moreover, this in-ventory model had an extra step in the scope of inspection; which occurred after the rework process with no inspection error. To get closer to the practi-cal circumstances and to consider the uncertainty, the model was formulated in the fuzzy environment. The demand, rework, and inspection rates of the inventory system were considered as the triangular fuzzy numbers where the output factors of the inventory system were obtained via nonlinear parametric programming and Zadeh's extension principle. Finally, this scenario was illus-trated through a mathematical model. The concavity of the objective function was also calculated and the total profit function was presented to clarify the solution procedure by numerical examples.