THE DETERMINATION OF INVENTORY AND QUALITY INSPECTION POLICIES FOR SOLAR WATER HEATER RAW MATERIALS WITH CONSIDERING COMPONENT COMMONALITY AND DEFECTIVE FRACTION (Case Study: PT. Wijaya Karya Industri Energi)

• Main Author: Illona Siregar, Bella
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/36896
• Institution: Institut Teknologi Bandung

PT. Wijaya Karya Industri Energi (PT.WINNER) is one of the subsidiaries of PT. Wijaya Karya (Persero) Tbk which is engaged in the renewable energy industry. The products produced by the company are energy-based products by utilizing sunlight as their energy source. Solar Water Heater (SWH) is a superior product that provides the largest percentage of product sales to the company. The main components that make up SWH products are tanks and panels. Both of these components have different raw material structures. In this study the raw material reviewed was the raw material of SWH panel. This is because the problem of decreasing sales faced by the company in one of the SWH products (SWH 130L) is found in the performance of the panel, which produces less hot water. As a solution, the company's engineering bureau develops the raw material of SWH panels by considering the strategy of using common components in the structure of the raw material making up the product, known as the component commonality concept. The company also experiences problems related to the arrival of raw materials, namely the late delivery of raw materials by suppliers. This delay has caused the company to experience under stock raw material conditions resulting in line stop production. Problems become more complex with quality imperfections in the lot of raw materials received from suppliers. In 2017, it was known that there was a product defect of 4.25% of total sales which then resulted in losses for the company in the form of the cost of replacing new products in the amount of Rp. 914,906,201.00. The escape of this defective raw material as a result of the inspection process applied in the company has not been effective. The problems faced by PT. WINNER is very closely related to inventory management systems. Therefore, it is necessary to do an assessment related to the planning of raw materials in order to obtain effective policies. In this research, VMI (Vendor Managed Inventory) supply chain system will be studied to answer the problems faced by PT. WINNER. The characteristic of the VMI supply chain system is the coordination between suppliers and buyers in the supply chain. The successful implementation of the VMI system can be achieved by the existence of good cooperation and coordination between the two parties and the trust to share information. Calculation of optimal inventory policy will be carried out by considering the degree of communality of the component and the presence of defective fractions in the ordering lot. There are 5 (five) development models that represent the production method quality inspection methods. The objective function of the five models is to minimize the combined total cost of VMI inventory and quality inspection. The search for the optimum solution was done with the help of Lingo 12.0 software with a development model namely Non Linear Programming (NLP). Model of Inventory VMI and inspection integration which is chosen in order to minimize total inventory VMI and quality cost is Inventory Model of Acceptance Sampling without Replacement with the expectation of total cost is Rp 9.080.203.513,60 per year. This policy results in 20,90% holding-cost saving, 57,51% shortage-cost saving, 53,08% quality-cost saving, and 98.26% order-cost increasing compared to existing costs at PT. WINNER. This cost saving is obtained because in the VMI supply chain system with considering component communality it is possible for a shorter lead time to occur which reduces inventory costs in the form of decreasing the cost of storing security reserves and the possibility of shortages of raw materials.