การจัดการสินค้าคงคลังของบริษัท ศูนย์อะไหล่ยนต์ ลำพูน จำกัด

Abstract

This independent study aimed to improve inventory management of Lamphun Spare Parts Center Company Limited in order to keep full costing the lowest with appropriate quantity of inventory. This study applied the ABC Analysis to classify the inventory; the Economic Order Quantity (EOQ) to calculate the quantity for each order; and the Reorder Point (ROP) to identify period of time to place a new order to replenish an inventory stock. In this study, spare parts listed in the engine category were selected to be analyzed. According to the ABC Analysis, the selected spare parts were divided into 3 groups: Group A, Group B, and Group C, of which the ratio was presented as 75:20:5. Group A consisted of 207 product items, which costed 581,074.54 Baht in total. According to the EOQ calculation on the basis of product demands as acquired by the Coefficient of Variation Analysis, 197 of them were the items with the fixed-order demand and could be calculated for the EOQ. The order quantities of these items were modified according to the lot size of actual purchase and the quantity discount condition. The ROP and the safety stock of these items were, then, calculated under the consideration of 4 selected service levels: 84%, 90%, 95%, and 99%. Since the selection of service level was based upon the full costing, this study, thus, chose the service level at 84% as it could keep the full costing the lowest. This selected service level was, however, lower than the level of retailed business service standard due to product redundancy caused by diversity of product qualities and brands. According to the calculation, the inventory quantity was averagely cut down to 994,087.19 Baht; the carrying cost was decreased to 113,744.31 Baht; and the ordering cost was reduced to 174,713.01 Baht. Consequently, after this study was conducted, the full costing was 288,457.32 Baht, which was lower than the previous full costing at 84,105.73 Baht.