justo a tiempo y kanbam

7/29/2019 Justo a Tiempo y KANBAM

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The M cGraw -H i l l Companies, Inc., 2004

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Just-in-Time and Lean Systems


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JIT Defined

The Toyota Production System

JIT Implementation Requirements

JIT in Services

OBJECTIVES


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Just-In-Time (JIT)

Defined

JIT can be defined as an integrated set of

activities designed to achieve high-volumeproduction using minimal inventories (rawmaterials, work in process, and finished

goods) JIT also involves the elimination of waste in

production effort

JIT also involves the timing of productionresources (i.e., parts arrive at the next

workstation just in time)


4/31The M cGraw -H i l l Companies, Inc., 2004

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JIT and Lean Management

JIT can be divided into two terms: Big JIT andLittle JIT

Big JIT (also called Lean Management) is aphilosophy of operations management that seeksto eliminate waste in all aspects of a firmsproduction activities: human relations, vendorrelations, technology, and the management ofmaterials and inventory

Little JIT focuses more narrowly on schedulinggoods inventory and providing service resourceswhere and when needed



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JIT Demand-Pull Logic

Customers

Sub

Sub

Fab

Fab

Fab

Fab

Vendor

Vendor

Vendor

Vendor

Final

Assembly

Here the customer starts

the process, pulling an

inventory item from

Final Assembly

Here the customer starts

the process, pulling an

inventory item fromFinal Assembly

Then sub-assembly work is

pulled forward by

that demand

Then sub-

assembly work is

pulled forward by

that demand

The process continues

throughout the entire

production process andsupply chain

The process continues

throughout the entire

production process and

supply chain

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The Toyota Production System

Based on two philosophies: 1. Elimination of waste

2. Respect for people

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Waste in Operations

1. Waste from overproduction

2. Waste of waiting time

3. Transportation waste

4. Inventory waste

5. Processing waste

6. Waste of motion

7. Waste from product defects

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Minimizing Waste:

Focused FactoryNetworks

CoordinationSystem Integration

These are small specialized

plants that limit the range

of products produced

(sometimes only one type of

product for an entire

facility)

These are small specialized

plants that limit the range

of products produced

(sometimes only one type of

product for an entire

facility)

Some plants inJapan have as

few as 30 and

as many as

1000 employees

Some plants in

Japan have as

few as 30 and

as many as

1000 employees

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Minimizing Waste: Group Technology (Part 1)

UsingDepartmental Specialization for plant layout can cause a lot of

unnecessary material movement

UsingDepartmental Specialization for plant layout can cause a lot of

unnecessary material movement

Saw Saw

Lathe PressPress

Grinder

LatheLathe

Saw

Press

Heat Treat

Grinder

Note how the flow lines are going back and forthNote how the flow lines are going back and forth

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Minimizing Waste:

Group Technology (Part 2) Revising by using Group Technology Cells can reduce movement and

improve product flow

Revising by using Group Technology Cells can reduce movement andimprove product flow

Press

Lathe

Grinder

Grinder

A

2

BSaw

Heat Treat

LatheSaw Lathe

PressLathe

1

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Minimizing Waste:

Uniform Plant Loading (heijunka)

Not uniform Jan. Units Feb. Units Mar. Units Total

1,200 3,500 4,300 9,000

Uniform Jan. Units Feb. Units Mar. Units Total

3,000 3,000 3,000 9,000

Suppose we operate a production plant that produces a single

product. The schedule of production for this product could be

accomplished using either of the two plant loading schedules

below.

Suppose we operate a production plant that produces a single

product. The schedule of production for this product could be

accomplished using either of the two plant loading schedules

below.

How does the uniform loading help save labor costs?How does the uniform loading help save labor costs?

or

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Minimizing Waste: Just-In-Time

Production

Management philosophy

Pull system though the plant

WHAT IT IS

Employee participation Industrial engineering/basics

Continuing improvement

Total quality control Small lot sizes

WHAT IT REQUIRES

Attacks waste Exposes problems and bottlenecks

Achieves streamlined production

WHAT IT DOES

Stable environment

WHAT IT ASSUMES

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Minimizing Waste: Inventory

Hides Problems

Work in

processqueues

(banks)

Change

orders

Engineering design

redundancies

Vendor

delinquencies

Scrap

Design

backlogs

Machine

downtime

Decision

backlogs

Inspection

backlogs

Paperwork

backlog

Example: By

identifying defective

items from a vendorearly in the

production process

the downstream work

is saved

Example: Byidentifying defective

work by employees

upstream, the

downstream work issaved

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Minimizing Waste: Kanban Production

Control Systems

Storage

Part A

Storage

Part AMachine

CenterAssembly

Line

Material Flow

Card (signal) Flow

Withdrawal

kanban

Once the Production kanban is

received, the Machine Center

produces a unit to replace the

one taken by the Assembly Line

people in the first place

This puts thesystem back

were it was

before the item

was pulled

The process begins by the Assembly Line

people pulling Part A from Storage

Production kanban

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Determining the Number of Kanbans

Needed Setting up a kanban system requires

determining the number of kanbans cards (orcontainers) needed

Each container represents the minimumproduction lot size

An accurate estimate of the lead time requiredto produce a container is key to determining

how many kanbans are required

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The Number of Kanban Card Sets

C

SDL

k

)(1

containertheofSizestockSafetytimeleadduringdemandExpected

+=

+=

k = Number of kanban card sets (a set is a card)

D = Average number of units demanded over some time

period

L = lead time to replenish an order (same units of time asdemand)

S = Safety stock expressed as a percentage of demand

during leadtime

C = Container size

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Example of Kanban Card Determination:

Problem Data A switch assembly is assembled in batches of 4 units

from an upstream assembly area and delivered in

a special container to a downstream control-panel

assembly operation

The control-panel assembly area requires 5 switchassemblies per hour

The switch assembly area can produce a container ofswitch assemblies in 2 hours

Safety stock has been set at 10% of needed inventory

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Example of Kanban Card

Determination: Calculations

3or,75.2

4

5(2)(1.1))(1

containertheofSize

stockSafetytimeleadduringdemandExpected

==+

=

+

=

C

SDL

k

Always round up!

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Respect for People

Level payrolls

Cooperative employee unions

Subcontractor networks

Bottom-round management style

Quality circles (Small Group InvolvementActivities or SGIAs)

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Toyota Production Systems Four Rules

1. All work shall be highly specified as to content,sequence, timing, and outcome

2. Every customer-supplier connection must be direct, andthere must be an unambiguous yes-or-no way to send

requests and receive responses

3. The pathway for every product and service must be

simple and direct

4. Any improvement must be made in accordance with the

scientific method, under the guidance of a teacher, at the

lowest possible level in the organization

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JIT Implementation Requirements:

Design Flow Process

Link operations

Balance workstation capacities

Redesign layout for flow

Emphasize preventive maintenance

Reduce lot sizes

Reduce setup/changeover time

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JIT Implementation Requirements: Total

Quality Control

Worker responsibility

Measure SQC

Enforce compliance

Fail-safe methods

Automatic inspection

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Stabilize Schedule

Level schedule

Underutilize capacity

Establish freeze windows

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Kanban-Pull

Demand pull

Backflush

Reduce lot sizes

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JIT Implementation Requirements: Work

with Vendors

Reduce lead times

Frequent deliveries

Project usage requirements

Quality expectations

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Reduce Inventory More

Look for other areas

Stores

Transit

Carousels

Conveyors

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Improve Product Design

Standard product configuration

Standardize and reduce number of parts

Process design with product design

Quality expectations

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Concurrently Solve Problems

Root cause

Solve permanently

Team approach

Line and specialist responsibility

Continual education

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Measure Performance

Emphasize improvement

Track trends

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JIT in Services (Examples)

Organize Problem-Solving Groups

Upgrade Housekeeping

Upgrade Quality

Clarify Process Flows

Revise Equipment and Process Technologies

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JIT in Services (Examples)

Level the Facility Load

Eliminate Unnecessary Activities

Reorganize Physical Configuration

Introduce Demand-Pull Scheduling

Develop Supplier Networks

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