1

Just-in-Time/Lean Production

A repetitive production system

in which the processing and movement of materials and goods occur

just as they are needed!

2

Pre-JIT: Traditional Mass Production

Big lot sizesLots of inventory”PUSH” material to nextstage

Lowerper unit

cost

Big purchase shipments

Big “pushes” of finished goodsto warehouses or customers

???

3

Post-JIT: “Lean Production”

Tighter coordination along the supply chainGoods are pulled along

— only make and ship what is neededSmaller lotsFaster setupsLess inventory, storage space”PULL” material to next stage

Minimalor no

inventoryholding

cost

Smaller shipments

Goods are pulled out ofplant by customer demand

4

JIT Goals(throughout the supply chain)

• Eliminate disruptions

• Make the system flexible

• Reduce setup times and lead times

• Minimize inventory

• Eliminate waste

5

WasteDefinition:

Waste is ‘anything other than the minimum amount of equipment, materials, parts, space, and worker’s time, which are absolutely essential to add value to the product.’

— Shoichiro Toyoda President, Toyota

6

Forms of Waste:

• Overproduction

• Waiting time

• Transportation

• Processing

• Inventory

• Motion

• Product Defects

7

Inventory as a Waste

• Requires more storage space

• Requires tracking and counting

• Increases movement activity

• Hides yield, scrap, and rework problems

• Increases risk of loss from theft, damage, obsolescence

8

Building Blocks of JIT

• Product designStandard partsModular designQuality

• Process design• Personnel and organizational elements• Manufacturing planning and control

MPC

Staff ORG

Process Design

Product Design

9

Process Design

• “Focused Factories”

• Group Technology

• Simplified layouts with little storage space

• Jidoka and Poka-Yoke

• Minimum setups

10

Personnel and Organizational Elements

• Workers as assets

• Cross-trained workers

• Greater responsibility at lower levels

• Leaders as facilitators, not order givers

11

Top Management

Long-term planningProduct line decisions

Expansion issues

Middle management

Planning, purchasinghiring, and capital decisions

Monitor costs

Supervisors

Control activities in specific areasMonitor quality, delivery, etc.

Direct Labor

Perform predetermined tasks

Technical Staff

Work methods, QCProcess improvements,

MIS

Planning Info

Control Info

Detailed Methods,Schedules

Classic Organizational View

12

JIT Organization View

Top Management

Long-term planningProduct line decisions

Expansion issues

Middle management

Planning, less purchasinghiring, and capital decisions

Monitor costs and assist labor

Direct Labor (self-supervising)

Task performance and schedule attainmentControl specific areas of activity

Monitor quality, delivery, etc.Participate in hiring and continuous

improvement

Technical Staff

Training and TechnicalSupport

Planning Info

Control Info

Te

chn

ica

l Id

eas

13

Planning and Control Systems

• “Small” JIT

• Stable and level schedules

– Mixed Model Scheduling

• “Push” versus “Pull”

– Kanban Systems

14

Kanban

Uses simple visual signals to control production

• Examples:

empty slot in hamburger chute

empty space on floor

kanban card

15

Kanban Example

Workcenter B uses parts produced by Workcenter A

How can we control the flow of materials so that B alwayshas parts and A doesn’t overproduce?

Workcenter A Workcenter B

16

When a container is opened by Workcenter B, its kanban card is removed and sent back to Workcenter A.This is a signal to Workcenter A to produce another box of parts.

Kanban card: Signal to produceWorkcenter A Workcenter B

Kanban Card

17

Empty Box: Signal to pull

Empty box sent back. Signal to pull another full box intoWorkcenter B.Question: How many kanban cards here? Why?

Workcenter A Workcenter B

18

How Many Kanbans?

y = number of kanban cardsD = demand per unit of timeT = lead timeC = container capacityX = fudge factor

Cx)DT(1

y

19

Example

• Hourly demand = 300 units• Lead time = 3 hours• Each container holds 300 units• Assuming no variation in lead-time or

demand (x = 0):

y = (300 3) / 300 = 3 kanban cards

20

Extending the pull system

B

A

21

Note:

• For a kanban system to work, we NEED CONSISTENT demand across the work centers

• How do we ensure this?

22

Mixed Model Sequencing

Largest integer that divides evenly into daily requirement is 10:

A: 40 / 10 = 4B: 40 / 10 = 4C: 10 / 10 = 1

Mixed model sequence: A-B-A-B-A-B-A-B-C

Product Monthly Demand

Daily Requirement

A 800 40

B 800 40

C 200 10

23

Implementing JIT

EliminateSurprises

IncreaseFlexibility

Simplify

Drive OutWaste

What about automation?

24

Putting the Squeeze on Resources

Squeeze!

– Simplify– Eliminate Uncertainty– Increase Flexibility

NO

PAIN? YES