Analysis of Raw Material Inventory Planning Considering Uncertainty Demands (Case Study: Model Q with Back Order at PT. X)

Abstract

In the production process a variety of products owned by PT. X are very high because the company does not have the same product to make every day. In the delivery of raw materials by suppliers there is also a delay in delivery caused by the empty stock of raw materials at the supplier and also the pre-order purchasing system. Problems with PT. X are planning demand and raw material inventory by considering demand uncertainly. As a first step in choosing the right inventory policy method, the Kolmogorov-Smirnov Test for normality test and ADI (Average Demand Interval) test are the classification of raw materials based on demand patterns. Of the five types of raw materials, the ADI value is 0, 91 and 1, which means < 1, 32. So that the completion of raw material inventory planning is done by probabilistic inventory policy method Continuous Review (Q) Back Order with Hadley - Within algorithm. The results of data processing are known to be the level of service of each type of raw material with the calculation of the proposed method, the average value of the service level for the five types of raw materials studied reaches 99, 30%. Where the probabilistic method of the Continuous Review System (Q) Hadley-Within algorithm, provides savings of 7,75% of the total cost of the existing inventory of the company.