JIT Lean Production

8/12/2019 JIT Lean Production

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Just-in-Time/Lean Production

A repetitive production systemin which the processing and movement

of materials and goods occur

just as they are needed!


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Pre-JIT: Traditional Mass Production

Big lot sizes

Lots of inventory

PUSH material to next

stage

Lower

per unitcost

Big purchase shipments

Big pushes of finished goods

to warehouses or customers

???


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Post-JIT: Lean Production

Tighter coordination along the supply chain

Goods are pulled along

only make and ship what is needed

Smaller lots

Faster setups

Less inventory, storage space

PULL material to next stage

Minimal

or no

inventory

holding

cost

Smaller shipments

Goods are pulled out of

plant by customer demand


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JIT Goals(throughout the supply chain)

Eliminate disruptions

Make the system flexible

Reduce setup times and lead times

Minimize inventory

Eliminate waste


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Waste

Definition:

Wasteis anything other than the minimum

amount of equipment, materials, parts,

space, and workers time, which are

absolutely essential to add value to the

product.

Shoichiro Toyoda

President, Toyota


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Forms of Waste:

Overproduction

Waiting time

Transportation

Processing

Inventory

Motion

Product Defects


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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


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Building Blocks of JIT

Product design

Standard parts

Modular design

Quality

Process design

Personnel and organizational elements

Manufacturing planning and control

MPC

Staff ORG

Process Design

Product Design


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Top Management

Long-term planningProduct line decisions

Expansion issues

Middle management

Planning, purchasinghiring, and capital decisions

Moni tor costs

Supervisors

Control activities in specific areasMonitor qual i ty, del ivery, etc.

Direct Labor

Perform predetermined tasks

Technical Staff

Work methods, QCProcess improvements,

MIS

Planning Info

Control Info

Detailed Methods,

Schedules

Classic Organizational View


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JIT Organization View

Top Management

Long-term planningProduct line decisions

Expansion issues

Middle management

Planning, less purchasinghiring, and capital decisionsMoni tor cos ts and assis t 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

TechnicalIdeas


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Planning and Control Systems

Small JIT

Stable and level schedules

Mixed Model Scheduling

Push versus Pull

Kanban Systems


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Kanban Example

Workcenter B uses parts produced by Workcenter A

How can we control the flow of materials so that B always

has parts and A doesnt overproduce?

Workcenter A Workcenter B


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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 produce


Kanban Card


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Empty Box: Signal to pull

Empty box sent back. Signal to pull another full box into

Workcenter B.

Question: How many kanban cards here? Why?



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How Many Kanbans?

y = number of kanban cards

D = demand per unit of time

T = lead timeC = container capacity

X = fudge factor

C

x)DT(1y


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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


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Note:

For a kanban system to work, we NEED

CONSISTENTdemand across the work

centers

How do we ensure this?


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Mixed Model Sequencing

Largest integer that divides evenly into daily

requirement is 10:

A: 40 / 10 = 4

B: 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


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Implementing JIT

Eliminate

Surprises

Increase

FlexibilitySimplify

Drive Out

Waste

What about

automation?


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Putting the Squeeze on Resources

Squeeze!

Simplify

Eliminate Uncertainty

Increase Flexibility

NO

PAIN? YES

Documents

JIT Lean Production