การปรับปรุงการพยากรณ์ความต้องการวัตถุดิบและนโยบายการเติมเต็มวัตถุคงคลังสำหรับโรงงานผลิตขึ้นรูปเหล็กหล่อแบบออกแบบตามคำสั่งซื้อ / อัจฉรา จันวดี = Improvement of demand forecasting and replenishment policy of raw materials for an engineer-to-order cast iron manufacturer / Auschara Junvadee
A cast iron manufacturer designs and manufactures products to serve customer’ orders almost exclusively as machinery spare parts. Most of the orders are Engineer-to-Order products which require both designing and manufacturing services. The demand is often unpredictable in the sense that its variation. To ensure on-time delivery and to improve customer service, the cast iron manufacturer must maintain adequate stock of raw materials. This paper examines a case study of a cast iron manufacturer and the shortage of raw materials and overstocking of inventory issues it often faces. The objective of this study is to improve the efficiency of its inventory management system of raw materials to avoid excess or shortage of inventory. The research is conducted in two phases which are forecasting raw materials demands and determining the replenishment policies. We develop demand forecasting models to minimize forecasting errors using time series method. The accuracy of the forecast is then measured in terms of Mean Absolute Percentage Error (MAPE) and Mean Squared Error (MSE). Found that Autoregressive Integrated Moving Average method (ARIMA) has given best results as reducing forecasting error by 34%. The replenishment policy found that best result is to develop and determine Ordering point and Quantity by mathematics model. And the results are increment of service level to 94%, decrement of shortage by 23% and reducing overall cost by 19%.
