Abstract:
The objective of this thesis is to study demand forecasting and production planning. The case study company manufactured the product that was made to stock. The most significant problem was the decision about the merchandise procution monthly. Only experienced decision maker was counted. No previous document was statistically analyzed. This caused the problems of excessive production than demand and it increased the expenditure of inventory and product depreciation. To design the system, the sales data was studied in order to choose the appropriate forecasting technique for the sales data. Furthermore, the proposed system reduced the cost of MRP production plan which was 743,389 THB monthly or 13,381,000 THB annually whereas the current system experditure was 886,333 THB monthly or 15,954,000 THB annually. To sum up, the proposed system which is Decomposition (Additive trend plus seasonal), is more beneficial. The collection of data from July 08 till December 09 has been studied (Which was 18 months period). It revealed that the total sales numbers were 28,170,000 units where as the 28,056,000 units were forecasted by new system. The ration variant(2) was equal to 5,148x10(3)