Inventory Management

Introduction Basic definitions ? An inventory is an accumulation of a commodity that will be used to satisfy some future demand. Inventory appears in several forms : raw material, work in process, finished product

Why Inventory Management ? May have significant impact on customer service level and system widecost Distribution and inventory (logistics) costs are quite substantial Example : Value of inventories in U.S.~ $ 1 trillion (1993) Approximately 16 % of total assets are tied in inventories(1986) Spare parts (service parts) inventories of a typical manufacturer ~ $ 5 million - $ 15 million Service industries hold stocks for supplies

Introduction Why hold inventory ? Unexpected changes in customer demand Uncertainty in the quantity and quality of the supply, cost, delivery Economies of scale offered by transportation cost Two important issues in inventory management 1.Demand forecasting 2.Order quantity calculation

Decision making in production and inventory management involves dealing with large number of items, with very diverse characteristics and with external factors. We want to resolve: (1)How often the inventory status (of an item) should be determined ? (2)When a replenishment order should be placed ? (3)How large the replenishment order should be ? Goals

Factor affecting The key factor affecting inventory policy : Customer demand (forecasting, variability) Replenishment lead time The number different product The length of planning horizon Cost 1. order cost : cost of product + transportation cost 2. inventory holding cost

Type of inventory Functional classification Cycle Inventories: produce or buy in larger quantities than needed. –Economies of scale –Quantity discounts –Restrictions (technological, transportation,…) inventory time cycle stock a cycle

Type of inventory Safety Stock: Provides protection against irregularities and uncertainties. Anticipation stock: low demand in one part of the year build up stock for the high demand season. Persediaan yang dibutuhkan untuk mengantisipasi kenaikan permintaan Hedge inventories : expect changes in the conditions (price, strike, supply, etc.) Pipeline (or work-in-process) inventories: goods in transit, between levels of a supply chain, between work stations. Persediaan yang muncul karena lead time pengiriman dari satu tempat ke tempat lain.

Alat ukur persediaan Ukuran kinerja persediaan 1.Inventory turnover : kecepatan barang mengalir dibanding jumlah rata-rata persediaan 2.Inventory days of supply jumlah hari, dimana operasi masih dapat berlangsung dengan tingkat persediaan yang ada 3.Fill rate persentase jumlah persediaan yang tersedia untuk memenuhi permintaan pelanggan

Klasifikasi Persediaan Bentuk persediaan berdasarkan klasifikasi 1.Bentuk 2.Fungsi 3.Ketergantungan

TUGAS Buatlah beberapa model persediaan yang Anda ketahui Presentasi dua minggu yang akan datang Model Persediaan