Introducción al Planeamiento agregado - Teoría y ejemplo

• A large variety of products:

• Example 1: IBM (desktops, laptops, mainframes, special-purpose computers, etc; furthermore, many models for each of the above categories)

• Example 2: Ford (sedans, SUV’s minivans, trucks, etc; again, many models and variations in each category)

• Product structure: An assembly of a number of components and subassemblies

• Example:

• (Desktop) Computer

• Motherboard

• CPU-card

• I/O card

• Modem card

• Power supply unit

• Ventilator

• etc.

• Monitor

• Keyboard

• Mouse

• (other peripherals)

• Some components and subassemblies are produced in-house, and some are procured from outside.

Bill of Materials (BOM)

Raw

Material

& Comp.

Inventory

Finished

Item

Inventory

S1,2S1,1 S1,n

S2,1 S2,2 S2,m

Assembly Line 1: Product Family 1

Assembly Line 2: Product Family 2

Backend Operations

Dept. 1 Dept. 2 Dept. k

S1,i

S2,i

Dept. j

Aggregate Planning

Master Production Scheduling

Materials Requirement Planning

Aggregate Unit

Demand

End Item (SKU)

Demand

Corporate Strategy

Capacity and Aggregate Production Plans

SKU-level Production Plans

Manufacturing

and Procurement

lead times

Component Production lots and due dates

Part process

plans

(Plan. Hor.: 1 year, Time Unit: 1 month)

(Plan. Hor.: a few months, Time Unit: 1 week)

(Plan. Hor.: a few months, Time Unit: 1 week)

Shop floor-level Production Control(Plan. Hor.: a day or a shift, Time Unit: real-time)

• Effective Data Collection and Maintenance/Data Integrity: There is a need for a monitoring tool that will provide a centralized, correct and efficient representation of the system status at any point in time.

• Industry Solution: Manufacturing Execution Systems (MES)

• e.g., SAP, Oracle, PeopleSoft

• Efficient and Coherent Computerized Planning Tools: There is a need for a suite of computationally efficient planning tools that will effectively address the problems arising at the various levels of the decomposition framework, while maintaining plan consistency across the different levels.

• Industry Solution: Product and Supply Chain Planning Software

• e.g., I2 Technologies, BAAN, Manugistics

•Items (or Stock Keeping Units - SKU’s): The final products delivered to the

(downstream) customers

•Families: Group of items that share a common manufacturing setup cost;

i.e., they have similar production requirements.

•Types: Groups of families with production quantities that are determined in a

single aggregate production plan.

•Aggregate Unit: A fictitious item representing an entire product type.

•Aggregate Unit Production Requirements: The amount of (labor) time

required for the production of one aggregate unit. This is computed by

appropriately averaging the labor time requirements over the entire set of

items represented by the aggregate unit.

•Aggregate Unit Demand: The cumulative demand for the entire set of items

represented by the aggregate unit.

Remark: Being the cumulate of a number of independent demand series, the

demand for the aggregate unit is a more robust estimate than its constituent

components.

Washing machine

Model Number

Required labor time

(hrs)

Item demand as % of

aggregate demand

A5532 4.2 32

K4242 4.9 21

L9898 5.1 17

3800 5.2 14

M2624 5.4 10

M3880 5.8 06

Aggregate unit labor time = (.32)(4.2)+(.21)(4.9)+(.17)(5.1)+(.14)(5.2)+

(.10)(5.4)+(.06)(5.8) = 4.856 hrs

Plan Agregado

Demanda en U.Q

Disponibilidad de

Unidades Equiva.

(Situación del

Invenario actual)

Plan Agregado de

producción

Capacidad

de Producción

Requerida

Requerimiento de laProducción en U.Q

Estrategia Corporativa

Plan Agregado de Producción:

•Niveles de la Producción Agregada

•Niveles del Inventario Agregado

•Niveles de los Pedidos pendiente Agregados

Plan de Capacidad de Producción:

•Nivel(es) Fuerza Laboral

•Nivel(es) Sobretiempo

•Cantidad de Subcontratados

1. Caza de la demanda: Variar el nivel de Fuerza Laboral

D(t) P(t) = D(t)

W(t)

PC WC HC FC

•D(t): Demanda Agregada

•P(t): Nivel de Producción Agregada

•W(t): Nivel de Fuerza de Trabajo Requerida

•Costos involucrados:

•PC: Costos de Producción

•Fijos(maquinaria, Gastos generales)

•Variable(materiales, consumibles, etc.)

•WC: Costo de trabajo regular

•HC: Costos de contratación: e.g., anuncios, entrevistas, capacitación

•FC: Costos de despidos: e.g., compensación, costo social

Estrategias de Planeamiento Agregado Puro

2. Variando la Capacidad para producir con empleados constantes.

D(t) P(t)

O(t)

PC WC OC UC

U(t)

S(t)

SC

W = ct•S(t): Cantidades subcontratadas (compradas a terceros)

•O(t): Número de horas extras.

•U(t): Undertime levels


•PC, WC: como lo anterior

•SC: Costo por subcontratar (tercerizar): e.g., purchasing, transport, quality, etc.

•OC: overtime costs: incremental cost of producing one unit in overtime

•(UC: undertime costs: this is hidden in WC)


3. Accumulating (Seasonal) Inventories:

D(t) P(t)

I(t)

PC WC IC

W(t), O(t), U(t), S(t) = ct

•I(t): Nivel de Inventario Acumulado


•PC, WC: como la anterior.

•IC: Costo por mantener Inventario: e.g., interest lost, storage space,

pilferage, obsolescence, etc.



4. Backlogging:

D(t) P(t)

B(t)

PC WC BC

W(t), O(t), U(t), S(t) = ct

•B(t): Niveles de Atrasos Acumulados


•PC, WC: igual que el anterior.

•BC: costos por atrasos (servicio, rotura de stock) : e.g., costos de agilización,

penalidades, ventas perdidas (actuales), insatisfacción de los clientes.

D(t)

P(t)

I(t-1)

PC WC

S(t)

SC

W = constante•D(t): Demanda Agregada


•I(t): Nivel de Inventario Acumulado

•B(t): Niveles de Atrasos Acumulados


•PC: Costos de Producción




•BC: costos por atrasos (servicio, rotura de stock)

Esquema general: Restricción 1

BC

I(t)

B(t)

B(t-1)

W(t-1)

H(t)


•H(t): Nivel de nuevos contratos

•F(t): Nivel de despidos laborales






W(t)

F(t)

5P(t)



•O(t): Numero de horas extra.

•WD(t): Número de días laborales en el mes t.


8*WD(t) *W(t)

O(t)

Introducción al Planeamiento agregado - Teoría y ejemplo

Engineering

Transcript of Introducción al Planeamiento agregado - Teoría y ejemplo