CARLOS A. MARINO DEL ROSARIO

Director Ingeniería Logística y de Transporte

Coordinador Master Supply Chain Engineering

GESTIÓN DE COMPRAS Y

PROVEEDORES

GESTIÓN DE INVENTARIOS, MODELOS DETERMINÍSTICOS Y ESTOCÁSTICOS

ABOUT MEDoctorando en Industrial and Systems Engineering, Mississippi State University (USA);

Master of Science Industrial Engineering & Operations Research, Mississippi State University (USA),

Master of Science Engineering Management, California State University East Bay (USA);

Master Transportation and Logistics Management Reverse Logistics, American Military University (USA);

Magister en Administración de Empresas, Universidad del Pacifico (PERU);

Ingeniero Industrial, Universidad de Lima (PERU).

Licenciado como Professional Industrial Engineer (P.E.) en el Estado de California (EE.UU.), ha seguido especializaciones avanzadas en proyectos en la Universidad de Stanford (EE.UU.) y Total Quality Management (Japón).

Director de la Carrera de Ingeniería Logística y de Transporte en la Universidad San Ignacio de Loyola

Coordinador de la Maestría en Supply Chain Engineering

Profesor de la Maestría UQAM-USIL

Cuenta con más de 25 años de experiencia a nivel directivo en la gestión del transporte, operaciones y logística para compañías norteamericanas como MFC Project Engineers, Índigo Piping Systems, ambas con operaciones globales en Asia, Medio Oriente, Latinoamérica, así como en empresas peruanas como la Embotelladora Latinoamericana S.A. y Nestlé Perú. Ha sido Gerente General de la RED IDI (Investigación, Desarrollo e Innovación) en Perú. Consultor de empresas como PWC, DHL y otras.

Agenda de LA SESIÓN

●Análisis ABC.●Aplicación.●Criterios.●Usos.●Análisis Lote Óptimo de Compra.●Caso de Estudio ●Conclusiones

Because the customer usually isn’t sitting at the plant exit!

Queen Elizabeth research station in Antarctica

Why do we have inventories?

Process Steps for Men’s Nylon Supplex Parka

Operations and Supply Processes

The integrated value-creation process must be managed across firms from end to end

DETERMINISTIC EOQINVENTORY MODELS

8

Inventory Costs

1. Holding (or carrying) costs• Costs for storage, handling, insurance, and

so on

2. Setup (or production change) costs• Costs for arranging specific equipment

setups, and so on

3. Ordering costs• Costs of placing an order

4. Shortage costs• Costs of running out

Independent Versus Dependent Demand

●Independent demand: the demands for various items are unrelated to each other• For example, a workstation may produce

many parts that are unrelated but meet some external demand requirement

●Dependent demand: the need for any one item is a direct result of the need for some other item• Usually a higher-level item of which it is part

Basic EOQ Model

●Demand for the product is constant and uniform throughout the period

●Lead time (time from ordering to receipt) is constant

●Price per unit of product is constant ●Inventory holding cost is based on

average inventory●Ordering or setup costs are constant●All demands for the product will be

satisfied

EOQ Assumptions

●Known & constant demand

●Known & constant lead time

●Instantaneous receipt of material

●No quantity discounts

●Only order (setup) cost & holding cost

●No stockouts

Inventory Holding Costs

Housing (building) cost 6%

Material handling costs 3%

Labor cost 3%

Inventory investment costs 11%

Pilferage, scrap, & obsolescence 3%Total holding cost 26%

% of Category Inventory Value

EOQ Model

Order Quantity

Annual Cost

Order Quantity

Annual Cost

Holding Cost

EOQ Model

Why Order Cost Decreases

●Cost is spread over more units

Example: You need 1000 microwave ovens

Purchase OrderDescription Qty.Microwave 1000

Purchase OrderDescription Qty.Microwave 1

Purchase OrderDescription Qty.Microwave 1

Purchase OrderDescription Qty.Microwave 1

Purchase OrderDescription Qty.Microwave 1

1 Order (Postage $ 0.35) 1000 Orders (Postage $350)

Order quantity

Order Quantity

Annual Cost

Holding Cost

Order (Setup) Cost

EOQ Model

Order Quantity

Annual Cost

Holding Cost

Total Cost Curve

Order (Setup) Cost

EOQ Model

Order Quantity

Annual Cost

Holding Cost

Total Cost Curve

Order (Setup) Cost

Optimal Order Quantity (Q*)

EOQ Model

How much to order

● Economic order quantity is the amount that balances the cost of ordering with the cost of maintaining average inventory• Assumes demand and

costs are relatively stable for the year

• Does not consider impact of joint ordering of multiple products

Annual Product Costs, Based on Size of the Order

H

SDEOQ

2

D = Annual demand (units)S = Cost per order ($) C = Cost per unit ($) I = Holding cost (%)H = Holding cost ($) = I x C

Economic Order Quantity

EOQ Model Equations

D = Demand per year

S = Setup (order) cost per order

H = Holding (carrying) cost

EOQ Example

You’re a buyer for SaveMart.

SaveMart needs 1000 coffee makers per year. The cost of each coffee maker is $78. Ordering cost is $100 per order. Carrying cost is 40% of per unit cost. Lead time is 5 days. SaveMart is open 365 days/yr.

What is the optimal order quantity & ROP?

SaveMart EOQ

H

SDEOQ

2

20.31$

100$10002 EOQ

D = 1000S = $100C = $ 78 I = 40%H = C x IH = $31.20

EOQ = 80 coffeemakers

1. Interest rates go up ?

2. Order processing is automated ?

3. Warehouse costs drop ?

4. Competitive product is introduced ?

5. Product is cost-reduced ?

6. Lead time gets longer ?

7. Minimum order quantity imposed ?

H

SDEOQ

2

What if …

Basic Fixed–Order Quantity Model

Place OrderLead time

Receive order

Use inventory

Ejemplo: Una ferretería vende 20.000 taladros al año. El costo anual de mantenimiento de existencias es de $5. El costo de hacer el pedido y recibir cada despacho es de $500. Por tanto, el EOQ es:

Ejercicio

Una compañía comercializadora adquiere de un proveedor externo cajas de chocolates belgas que distribuye en toda la meseta central del país. La empresa espera vender aproximadamente 100,000 cajas de estos chocolates durante el año. La demanda es relativamente constante durante el año. El costo asociado a los pedidos es de ¢25 por cada uno. La política de costo de inventario que la empresa ha utilizado tradicionalmente es cargar el 20% del costo de compra como costo anual de conservación de los inventarios, para cualquier artículo. El precio que se paga al proveedor por cada cada caja de chocolates es de ¢6.25

a) Determine la cantidad óptima de pedido y el costo total.b) Supóngase un tiempo de entrega de dos días, ¿cuál será el

punto de reorden? Utilice un año de 365 días.

Caso de Estudio:

Conclusiones

CARLOS A. MARINO DEL ROSARIO

Director Ingeniería Logística y de Transporte

Coordinador Master Supply Chain Engineering

GESTIÓN DE COMPRAS Y

PROVEEDORES

GESTIÓN DE INVENTARIOS, MODELOS DETERMINÍSTICOS Y ESTOCÁSTICOS