Mia Octaviana (1), Enny Aryanny (2)
General Background: Raw material inventory control is essential in manufacturing because poor stock management can increase storage requirements, material deterioration, and operational costs. Specific Background: A knock-down furniture manufacturer experienced overcapacity in particle board storage, where accumulated remaining stock reached 3,494 sheets or 60 pallets, exceeding the available warehouse capacity of 48 pallets. Knowledge Gap: Previous inventory studies have commonly applied optimization methods to conventional stock systems, while limited work integrates Lagrange Multiplier optimization with Holt-Winters forecasting under warehouse capacity constraints for particle board materials. Aims: This study aimed to optimize particle board inventory control by minimizing total inventory cost while considering storage capacity limitations. Results: The company method required 133.21 m³ of storage space and generated total inventory cost of Rp 64,882,040. EOQ calculation produced infeasible space requirements because it did not simultaneously consider capacity constraints. The Lagrange Multiplier method reduced storage requirements to 128.59 m³ and lowered total inventory cost to Rp 61,349,841, producing savings of Rp 3,532,199 or 5.45%. Holt-Winters generated the lowest MAD values and was selected for demand forecasting, producing optimal order quantities of 425 sheets for 25 mm, 629 sheets for 15 mm, and 1,926 sheets for 12 mm particle board. Novelty: This study combines Holt-Winters forecasting and Lagrange Multiplier optimization for multi-item raw material control with limited warehouse capacity. Implications: The findings support more efficient purchasing decisions, improved warehouse utilization, and lower raw material inventory expenses.
Highlights:
Keywords: Inventory, Lagrange Multiplier, Manufacturing, Warehouse Capacity
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