Miktar İndirimli Stok Modeli İçin Döviz Kuru Tahmini: Ar-Ge Projelerinde Bir Uygulama

Abstract

The first action to be taken before making a production decision is to determine a budget in a production facility. Some problems arise if the budget is set incorrectly. It will be a waste of time, such as searching for a budget again, and at the same time, wrong production decisions can be made. While the incomplete determination of the budget causes loss of time, such as the creation of a budget again, overdetermination leads to the purchase of products that are not needed. The important thing to avoid such situations is to use a good cost estimation method. If planning personnel can accurately estimate production costs during the planning phase of production, it can provide the right resource allocation for productions as well as it will prevent high-cost products from being kept in excess stock since it can see the monetary value of surplus production . This will reduce stock costs and enable the business to better use its liquid resources. In this study, it is aimed to make cost estimations of the items procured from Sub-Contractors in R&D activities. These supply items are used in the assembly of various systems and subsystems within the enterprise. When needed during the purchasing process, offers are requested from the Subcontractor companies for the relevant items and, companies prepare price offers for these items. After, offers are considered and, an order is placed to a company determined according to availability. In this study, it is aimed to make a production plan by considering the costs of these products while determining the products to be produced in the planning stage before the proposal stage. Since the offers received from the subcontractors for the supply items are based on USD, it will be possible to decide whether to keep stock or not to keep stock. Thus, the need to estimate the costs of procurement items. The variable that most affects the cost of procurement items is the exchange rate. Increases in exchange rates are directly reflected in costs. For this reason, the exchange rate must be one of the determined variables in a forecasting model to be established. In order to predict the change in the exchange rate, the stages of the Box Jenkins model were examined first. Within the scope of literature research AR, MA, ARMA, ARIMA, ARCH, GARCH, EGARCH, TARCH univariate models and, ARDL, NARDL multivariate prediction models have been investigated. Among these models ARIMA, EGARCH and, NARDL models used in applications. When comparing established models, NARDL model was determined as the model with the highest explanatory power. Another variable is the quantity of the supply item to be ordered. Companies that sell some products sell higher volumes by providing price discounts in some periods. Thus, they may want to reduce their stocks or balance their production plans. For this purpose, they report that they will make a higher discount as the sales volume increases. In this study, Economic Order Quantity Model with Quantity Discount was examined and compared with the forecast model.