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Chapter 11

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-volume production using minimal inventories (raw materials, work in process, and finished goods)

• JIT also involves the elimination of waste in production effort

• JIT also involves the timing of production resources (i.e., parts arrive at the next workstation “just in time”)

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Characteristics of JIT

• JIT is popularly known as stockless production

• Produce just enough to meet demand

• Inventory is wasteful— Labor and materials— Equipment and time— Storage and insurance— Capital, etc.

• Quality must be at the source

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JIT and Lean Management

• JIT can be divided into two terms: “Big JIT” and “Little JIT”

• Big JIT (also called Lean Management) is a philosophy of operations management that seeks to eliminate waste in all aspects of a firm’s production activities: human relations, vendor relations, technology, and the management of materials and inventory

• Little JIT focuses more narrowly on scheduling goods inventory and providing service resources where 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 from Final 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 and supply chain

The process continues throughout the entire production process and supply chain

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The Japanese Approach to Productivity

• Imported technologies

• Efforts concentrated on shop floor

• Quality improvement focus

• Elimination of waste

• Respect for people

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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 Factory Networks

• Small specialized plants

• Thinner is better— Better control— Bolsters specialization and excellence— More economical to manage

• Large vertically integrated operations are:— Bureaucratic— Difficult to manage

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11Minimizing Waste:

Focused Factory Networks

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 in Japan 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

• Identification of:— Machine cells— Part families

• Based on similarities in:— Design— Manufacture

• Saves time and effort

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Minimizing Waste: Group Technology (Part 1)

• Using Departmental Specialization for plant layout can cause a lot of unnecessary material movement

• Using Departmental 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 and improve product flow

Press

Lathe

Grinder

Grinder

A

2

BSaw

Heat Treat

LatheSaw Lathe

PressLathe

1

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Minimizing WasteUse of Other Technologies

• Robotics• Supply chain management• Value stream mapping• Flexible manufacturing systems• Computer integrated manufacturing

systems• Expert systems• Neural networks

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Minimizing Waste: Quality at the Source

Self-inspection— Limited use of QC departments

Automated inspection

Line-stopping empowerment— Quality before quantity

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Minimizing Waste: JIT Production

Produce...

...what is needed...

...when it’s needed...

...NOTHING MORE!

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Minimizing Waste: Uniform Plant Loading

This does not mean building a single product.

But maintaining a stable mix of products,

and firm monthly schedules.

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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

UniformJan. 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 through 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 inprocess queues(banks)

Changeorders

Engineering designredundancies

Vendordelinquencies

Scrap

Designbacklogs

Machine downtime

Decisionbacklogs

Inspectionbacklogs

Paperworkbacklog

Example: By identifying defective items from a vendor early in the production process the downstream work is saved

Example: By identifying defective work by employees upstream, the downstream work is saved

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Minimizing Waste:Kanban Production Control System

• Uses signaling system to regulate JIT flows

• Kanban—sign or instruction card

• Kanban system is a pull system

— Authority to produce comes from downstream

— It is a form of information system

— Production kanban--can be single card if move distance is short

— Move (withdrawal, conveyance) kanban

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Kanban Production System

• Objectives

— Lead time reduction

— Lot size reduction

— Waste elimination

• One of several tools of Lean Mfg.

— Ineffective without others

— Prerequisites must be met

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Rules of Kanban Production System

• Withdraw only the quantity needed

• Produce only the quantity given by kanban

• Kanban is withdrawal/production authority

• Move only good parts

• Smooth and level production

• Decrease number of cards to reduce inventory

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Minimizing Waste: Kanban Production Control Systems

Storage Part A

Storage Part AMachine

Center Assembly 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 the system 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 (or containers) needed

• Each container represents the minimum production lot size

• An accurate estimate of the lead time required to 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

container theof Size

stockSafety timelead during demand Expected

C

SDL

k

)(1

container theof Size

stockSafety timelead during demand Expected

k = Number of kanban card sets (a set is a card)D = Average number of units demanded over some time periodL = lead time to replenish an order (same units of time as demand)S = Safety stock expressed as a percentage of demand during lead timeC = 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 switch assemblies per hour

• The switch assembly area can produce a container of switch 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 ,75.24

5(2)(1.1))(1

container theof Size

stockSafety timelead during demand Expected

C

SDL

k

3or ,75.24

5(2)(1.1))(1

container theof Size

stockSafety timelead during demand Expected

C

SDL

k

Always round up!

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Minimizing Waste: Minimized Setup Times

What are the consequences of long setup times?— Long manufacturing lead times— Increased cost— Reduced capacity

A requirement for small-lot-size, mixed-model production?— Practice more setups to reduce time/setup— Fixed production quantity--improves setup— SMED

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Respect for People

• Strive to maintain level payrolls

• Workers as assets

• Cooperative employee unions

• Subcontractor networks

• Bottom-round management style

• Quality circles (Small Group Involvement Activities or SGIA’s)

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Toyota Production System’s Four Rules

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

2. Every customer-supplier connection must be direct, and there 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

• Design for quality and quality at the source

• Worker responsibility/quality culture

• Measure SQC and use achievable goals

• Enforce compliance

• Fail-safe methods

• Automatic inspection

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JIT Implementation Requirements: Stabilize Schedule

• Level schedule– Pull materials into final assembly in uniform

pattern

• Underutilize capacity– Realized by removing excess inventory– Inventory less likely with quality and equipment

maintenance

• Establish freeze windows– Fixed schedule with no further changes possible

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JIT Implementation Requirements: Kanban-Pull

• Demand pull

• Backflush– Used to explode end item’s BOM to determine

how many of each product went into it

• Reduce lot sizes

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JIT Implementation Requirements: Work with Vendors

• Limited number of suppliers for better control

• Reduce lead times

• Frequent deliveries

• Project usage requirements

• Quality expectations

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JIT Requirements:Planning and Control

• Plan for quality

• Uniform production rate— Smooth flow of materials— Emphasize rate not capacity— Refocused productivity

Less expensive machines Push towards lot size of one

— Less expensive machines

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JIT Implementation Requirements: Reduce Inventory More

• Look for other areas

• Stores

• Transit

• Carousels

• Conveyors

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JIT Implementation Requirements: Improve Product Design

• Standard product configuration

• Standardize and reduce number of parts

• Process design with product design

• Quality expectations

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JIT Implementation Requirements: Concurrently Solve Problems

• Root cause • Solve permanently

• Team approach

• Line and specialist responsibility

• Continual education

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JIT Implementation Requirements: 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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Performance Measurement

•Quality levels

•Customer satisfaction

•Equipment effectiveness

•Supplier performance

•Throughput time

•Inventory levels

•Setup/lead time reduction

•Layout efficiency

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Other Tools: Visual Control (5s)

• Sort—Seiri (organization; find what’s not needed)

• Set in order—Seiton (place for everything)

• Shine—Seiso (cleanliness)

• Standardize—Seiketsu (develop/maintain stds.)

• Sustain—Shitsuke (self-discipline)

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The Clean Workplace

Schedule

Returns

Problems

Store ToolsClose to thePoint of use

ProceduresPosted

Part A Part B

Post all pertinentInformation

OutgoingHolding areas

Identified