THE MATHEMATICAL MODEL OF TWO TIERS SUPPLIER SELECTION UNDER MULTI SUPPLIER, MULTI PRODUCT, MULTI PERIOD, AND QUANTITY DISCOUNT (CASE STUDY OF HIJAB COMPANY)

• Main Author: Chairunisa Utari, Larissa
• Format: Theses
• Language: Indonesia
• Subjects: Teknik (Rekayasa, enjinering dan kegiatan berkaitan)
• Online Access: https://digilib.itb.ac.id/gdl/view/54354
• Institution: Institut Teknologi Bandung

This study develops a two-stage supplier selection model and calculates the amount of production at each supplier stage so that there is no excess total system costs and inventory shortages that will have an impact on the company's service level to consumers. The main reference model for selecting suppliers with multi-product, multi-supplier, multi-period and quantity discounts uses the Woarawichai, et al. (2017) model. This research adds the concept of two-stage supplier selection by considering multi-product, multi-supplier, multi-period, quantity discount on suppliers, budget per period, supplier capacity, company warehouse capacity, and fluctuating demand at each period during the planning horizon. Products 1 (one) and 2 (two) go through two stages of supplier selection (tailors and embroidery), while in Product 3 (three) only go through one stage of supplier selection (tailors). Each supplier has a supplier capacity and discount prices for various ranges of production quantities. The main reference model has been refined in order to describe the real condition of the company using the Yadollahi, et al. (2017) model regarding inventory in the zero period, the Woarawichai model (2011) regarding budget allocation, the Sambatt model, et al (2018) regarding warehouse capacity, the Ayhan and Kilic models ( 2015) regarding supplier capacity, Feylizadeh's model, et al. (2018) relates to two stages of suppliers, Soto's model, et al. (2017) relates to the selection of price breakers for suppliers. The optimal solution results for the mathematical model are for Product 1 (one), the supplier in stage 1 (one) uses tailors 2 (two) and 3 (three), while in stage 2 (two) uses embroider 1 (one). The optimal solution for Product 2 (two), the supplier in stage 1 (one) uses tailors 1 (one) and 3 (three), while in stage 2 (two) uses embroider 1 (one). The optimal solution for Product 3 (three), the supplier in stage 1 (one) uses Tailor 3 (three). Based on the results of the sensitivity analysis using a ratio approach with 26 datasets, it can be seen that the selection of suppliers (tailors and embroiders) and the size of the production lot for product i will be influenced by the capacity of the tailor, the capacity of the embroidery, sewing costs for tailor j, cost of embroidery at embroidery b, upper limit and below the tailor j, as well as the upper and lower limit of the embroidery b. The minimum total system cost is generated when using dataset 3. At computation time, if there is a change in the cost of embroidery parameters, the capacity of embroidery and tailors, the upper lower limit of embroidery and sewing, the computation time will be longer. The fastest computation time is generated when using datasets 2, 10, 13, 15, 16, and 18..