1. Dr. RAVI SHANKAR
Professor
Department of Management Studies
Indian Institute of Technology Delhi
Hauz Khas, New Delhi 110 016, India
Phone: +91-11-26596421 (O); 2659-1991(H); (0)-+91-9811033937 (m)
Fax: (+91)-(11) 26862620
Email: r.s.research@gmail.com
http://web.iitd.ac.in/~ravi1
SESSION#5a: Just-in-Time Systems (CFVG: 2012)
JUST IN TIME SYSTEMS IN
OPERATIONS MANAGEMENT
2. The philosophy of JIT can be traced back to
Henry Ford, but formalized JIT originated in
Japan as the Toyota Production System. W.
Edwards Deming’s lesson of variability
reduction was a huge influence.
The focus of JIT is to improve the
system of production by eliminating
all forms of WASTE.
Just-In-Time Philosophy
JIT is a long-term approach to process improvement. It uses
timeliness as a lever to lower costs, improve quality and improve
responsiveness. However, JIT requires enormous commitment. It
took Toyota more than 25 years to get right!
3. The Seven Zeros: To identify waste
• Zero Defects: Quality at the source
• Zero Lot Size: To avoid batching delays
• Zero Setups: To minimize setup delay and allow production in
small lots
• Zero Breakdowns: To avoid stopping tightly coupled line
• Zero Handling: To promote flow of parts
• Zero Lead Time: To ensure rapid replenishment of parts
• Zero Surging: Necessary in system without WIP buffers.
Waste exists unless all the following goals are achieved
4. 4
Lean Production
Lean Production 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)
Lean Production also involves the elimination of
waste in production effort
Lean Production also involves the timing of
production resources (i.e., parts arrive at the
next workstation “just in time”)
5. 4/10/20125 (c) Dr. Ravi Shankar, AIT (2008) 5
Just-in-Time (JIT) Mfg.
Producing just what is needed, when it is needed,
in the amount needed, with only the minimum
required materials, equipment, labor, and space.
6. 6
Pull System
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
7. 7
Features of Lean 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
8. 8
The Toyota Production System (TPS)
Based on two philosophies:
• 1. Elimination of waste
• 2. Respect for people
9. 9
Some Examples of Waste
• Watching a machine run
• Waiting for parts
• Counting parts
• Over-runs in production
• Moving parts over long distances
• Storing inventory
• Looking for tools
• Machine breakdown
• Rework
10. 10
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
11. 11
How Basic Elements of JIT
Contribute to the “system”
Pull (Kanban) production control system
• Produce only what is needed - only when it is needed
Small-lot production
• Faster through-put, greater flexibility
Quick setups
• Facilitates economical small-lot-size production
Flexible resources
• Facilitates cellular layouts, TPM, and Kaizen
Cellular layouts
• Retain relevant flexibility of job shop, obtain efficiency of
production line
12. 12
How Basic Elements of JIT
Contribute to the “system”
Uniform production
• Create and maintain a stable production system
Quality at the source
• Facilitates removal of “buffers” and contributes to
stability of the “system”
Total productive maintenance
• Contributes to stability of the “system”
Supplier networks
• Facilitates frequent, small quantity delivery of
materials
13. 13
Minimizing Waste: Inventory
Hides Problems
Work in
process
queues
(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 vendor
early in the
production process
the downstream work
is saved
Example: By
identifying defective
work by employees
upstream, the
downstream work is
saved
15. 15
To Expose Problems:
Reduce Inventory Levels
Poor
Quality
Unreliable
Supplier
Machine
Breakdown
Inefficient
Layout
Bad
Design
Lengthy
Setups
16. 16
Remove Sources of Problems and Repeat the
Process
Poor
Quality
Unreliable
Supplier
Machine
Breakdown
Inefficient
Layout
Bad
Design
Lengthy
Setups
17. 17
JIT Production:
Total Quality Control
Worker responsibility
Measure SQC
Enforce compliance
Fail-safe methods
Automatic inspection ....
18. 18
Quality At The Source
Jidoka is authority to stop production line
Andon lights signal quality problems
Under-capacity scheduling allows for planning,
problem solving & maintenance
Visual signals for production control makes
problems apparent to everyone
Poka-yoke (mistake-proofing) prevents defects
19. 19
Kaizen
Continuous improvement
Requires total employee involvement
Essence of JIT is willingness of workers to
• spot quality problems
• halt production when necessary
• generate ideas for improvement
• analyze problems
• perform different functions
20. 20
JIT Production:
Work with Vendors
Reduce lead times
Frequent deliveries
Project usage requirements
Quality expectations ....
21. 21
JIT Production:
Minimize Setup Times
What are the consequences of long setup times?
A requirement for small-lot-size, mixed-model
production? ....
22. 4/10/201222 (c) Dr. Ravi Shankar, AIT (2008) 22
JIT Production? Pull Systems? Kanban? … How does it all
relate?
“Kanban”
• Means “card” in Japanese
• It is a “pull” production system and used as the
means of production control in JIT
How kanbans work:
• When an order to produce a finished product is issued to the plant,
workers withdraw components from a “standard container” and
build the product.
• Each container has a kanban on it, which is sent to the upstream as
an authorization to produce.
• This in turn activates kanbans at that operation, sent to the next
operation upstream, and so on. The process goes all the way to
kanbans issued to the vendor to produce and/or ship.
• Computer control is unnecessary:
23. 23
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
24. 24
Kanban Card
46-281247p1
27” Al Rim
Qty
23
Stock Loc:
RIP 1
Line Loc:
Asm. 1
Unique Part #
Description
Kanban Qty
Where to find
part when bin
is empty Where to return
filled Kanban
25. 4/10/201225 (c) Dr. Ravi Shankar, AIT (2008) 25
Characteristics of Systems
Well-suited to JIT
Discrete parts produced in a highly
repetitive environment.
Fairly smooth demand pattern throughout
the year.
Setup times/costs that can be reduced.
High worker flexibility - solve problems
Close proximity to vendors.
26. 4/10/201226 (c) Dr. Ravi Shankar, AIT (2008) 26
JIT Philosophy Requires Strong Partnerships with Suppliers
Characteristics of true JIT buyer-supplier partnerships
• JIT requires fast and regular supply
• Cost not only factor in vendor selection: quality, flexibility and
delivery are also key factors.
• Preferred vendors offer small lot sizes, frequent deliveries
• JIT requires few to single suppliers to solidify partnerships
Typical Supplier Concerns
• Erratic schedules from customer
• Impact of small lot sizes - additional transportation costs.
• Proximity
28. The Lessons of JIT
•The production environment itself is a control
•Operational details matter strategically
•Controlling WIP is important
•Speed and flexibility are important assets
•Quality can come first
•Continual improvement is a condition for
survival
29. 29
Just-In-Time Production
• Management philosophy
• Pull system though the plant
• Management philosophy
• Pull system though the plant
WHAT IT IS
• Employee participation
• Industrial engineering/basics
• Continuing improvement
• Total quality control
• Small lot sizes
• Employee participation
• Industrial engineering/basics
• Continuing improvement
• Total quality control
• Small lot sizes
WHAT IT REQUIRES
• Attacks waste (time, inventory,
scrap)
• Exposes problems and bottlenecks
• Achieves streamlined production
• Attacks waste (time, inventory,
scrap)
• Exposes problems and bottlenecks
• Achieves streamlined production
WHAT IT DOES
• Stable environment• Stable environment
WHAT IT ASSUMES
....
