Determination of Plastic Membrane Demand Forecasting Method and Raw Material Inventory Control Policy (Case Study: PT. Kencana Tiara Gemilang)

PT Kencana Tiara Gemilang is a plastic manufacturer which accommodate the needs of agriculture, fisheries, marine, construction, and industrial sectors for plastic membrane. The main products of PT Kencana Tiara Gemilang are Geoprotec Geomembrane, Mulsa (Mulch), and Lembrane. PT Kencana Tiara Gemilang implements make-to-order production system, which means that PT Kencana Tiara Gemilang will start the production planning and production process after customer order receipt is received. The problem faced by PT Kencana Tiara Gemilang is the absence of proper product forecasts and raw material inventory management. Without an accurate forecasting method and a raw material inventory control policy, the company will not be able to estimate the future needs and demand accurately and to prepare the required resource in advance well. This research is focused on determining the proper demand forecasting method to estimate the demand in future period. The forecasting result will be used to compare four inventory control method: (s,Q) system, (s,S) system, (R,S) system, and (R,s,S) system to find the most efficient method. The result is that simple exponential smoothing is chosen as the forecasting method for three products (Mulsa-35-6-440, Mulsa-35-6-220, and PB- 80-3-3), the trend-corrected exponential smoothing is chosen for four products (Geomembrane - 500.6.50, PB-30-99-87, PB-80-7-4, and PB-80-5-4), and the SBA method is chosen for five products (Mulsa-27-6-560, DT - SGP - 30.69, Geomembrane - 300.6.50, Mulsa- 27-5-670, and PB-30-10-11). The selected raw material inventory control policy for Material 1 is the periodic review system (R,s,S) system, for Material 2 is the continuous review system (s,Q) system, for Material 3 is the periodic review system (R,S) system, and for Material 4 and Material 5 is the continuous review system (s,S) system