การปรับปรุงประสิทธิภาพการจัดการสินค้าคงคลังของบริษัทผลิตชิ้นส่วนยานยนต์

Abstract

Inventory management is essential for all businesses because having too few or too many raw materials can have negative effects on the business, such as stock-outs or product deterioration. The data gathered from the case study indicates that the case study company had ordered more raw materials than was used and had a high inventory holding period. This resulted in excess inventory and high inventory costs. This study aims to improve inventory management effectiveness by examining the order quantity for 112 raw material items in group AA, derived from level 2 of the ABC classification method of the case study company. Then, the variation coefficient (VC) of demand for raw materials was used to determine the ordering volume of raw materials based on the assumptions of the Peterson-Silver theory, which found that 86 items of the stable demand for raw materials were analyzed using the Economic Order Quantity (EOQ) method. For unstable demand, 17 items used the Silver-Meal (SM) method, and 9 items used the Part-Period Balancing (PBB) method. In addition, we analyzed safety stock levels and reorder points with order quantity analysis to prevent and avoid shortages. The total inventory cost of the case study was then calculated and compared to the company’s actual total inventory cost from 2019 to 2021, showing that this study could minimize total inventory costs. It also analyzes how the situation has changed. We performed the sensitivity analysis using the Monte Carlo simulation to find the critical inputs that will affect the total inventory cost (output) in an abnormal situation, such as the Coronavirus Disease (COVID-19). As a result, the total cost of raw materials in group AA that uses methods decreased by 44.58 percent in 2019, 44.52 percent in 2020, and 45.55 percent in 2021. The case study company’s conditions show that there is no shortage of raw materials.