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1 Outline Just-in-Time (JIT) Examples of Waste Some Elements of JIT LESSON 24: JUST -IN-TIME 2 Producing only what is needed and when it is needed A philosophy An integrated management system Just-in-time

LESSON 24: JUST-IN-TIME

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Page 1: LESSON 24: JUST-IN-TIME

1

Outline

• Just-in-Time (JIT)• Examples of Waste• Some Elements of JIT

LESSON 24: JUST-IN-TIME

2

• Producing only what is needed and when it is needed

• A philosophy

• An integrated management system

Just-in-time

Page 2: LESSON 24: JUST-IN-TIME

3

• Theme: eliminate all waste including the ones caused by:– inventory management – supplier selection– defective parts– scheduling of production and delivery– information system

Just-in-time

4

Examples Of Waste

• Watching a machine run• Waiting for parts• Counting parts• Overproduction• Moving parts over long

distances• Storing inventory• Looking for tools• Machine breakdown• Rework

Page 3: LESSON 24: JUST-IN-TIME

5

Some Elements Of JIT

1. Focused factory networks2. Grouped Technology: Cellular layouts3. Quality at the source4. Flexible resources5. Pull production system6. Kanban production control7. Small-lot production and purchase8. Quick setups9. Supplier networks

6

Cellular Layouts

• Group dissimilar machines in a cell to produce a family of parts

• Reduce setup time and transit time• Send work in one direction through the cell (resembling

a small assembly line)• Adjust cycle time by changing worker paths

Page 4: LESSON 24: JUST-IN-TIME

7

Cellular Layouts

Enter

Worker 1

Worker 2Worker

3

Exit

Key: Product routeWorker route

Machines

8

Original Process Layout

12

1

2

3

4

5

6 7

8

9

10

11

A B C Raw materials

Assembly

Page 5: LESSON 24: JUST-IN-TIME

9

Part Routing Matrix

Parts 1 2 3 4 5 6 7 8 9 10 11 12A x x x x xB x x x xC x x xD x x x x xE x x xF x x xG x x x xH x x x

Machines

10

Part Routing Matrix - Reordered

Parts 1 2 4 3 5 6 7 8 9 10 11 12A x x x x xB x x x xC x x xD x x x x xE x x xF x x xG x x x xH x x x

Machines

Page 6: LESSON 24: JUST-IN-TIME

11

Parts 1 2 4 3 5 6 7 8 9 10 11 12A x x x x xD x x x x xB x x x xC x x xE x x xF x x xG x x x xH x x x

Machines

Part Routing Matrix - Reordered

12

Parts 1 2 4 8 3 5 6 7 9 10 11 12A x x x x xD x x x x xB x x x xC x x xE x x xF x x xG x x x xH x x x

Machines

Part Routing Matrix - Reordered

Page 7: LESSON 24: JUST-IN-TIME

13

Parts 1 2 4 8 3 5 6 7 9 10 11 12A x x x x xD x x x x xF x x xB x x x xC x x xE x x xG x x x xH x x x

Machines

Part Routing Matrix - Reordered

14

Parts 1 2 4 8 10 3 5 6 7 9 11 12A x x x x xD x x x x xF x x xB x x x xC x x xE x x xG x x x xH x x x

Machines

Part Routing Matrix - Reordered

Page 8: LESSON 24: JUST-IN-TIME

15

Parts 1 2 4 8 10 3 6 9 5 7 11 12A x x x x xD x x x x xF x x xC x x xG x x x xB x x x xE x x xH x x x

Machines

Part Routing Matrix - Reordered

16

Cellular Layout Solution

12

12 3

4

5

6

7

8 910

11

A BCRaw materials

Cell1 Cell 2 Cell 3

Assembly

Page 9: LESSON 24: JUST-IN-TIME

17

Advantages of Cellular Layouts

• Reduced material handling and transit time

• Reduced setup time

• Reduced work-in-process inventory

• Better use of human resources

• Easier to control

• Easier to automate

18

Disadvantages of Cellular Layouts

• Inadequate part families

• Poorly balanced cells

• Expanded training and scheduling of workers

• Increased capital investment

Page 10: LESSON 24: JUST-IN-TIME

19

Quality At The Source

• Jidoka is the authority to stop a production line• Andon lights signal quality problems• Undercapacity scheduling allows for planning,

problem solving & maintenance• Visual control makes problems visible• Poka-yoke prevents defects

20

Kaizen

• Continuous improvement• Requires total employment involvement• The essence of JIT is the willingness of workers to

• spot quality problems,• halt production when necessary,• generate ideas for improvement,• analyze problems, and • perform different functions

Page 11: LESSON 24: JUST-IN-TIME

21

Flexible Resources

• Multifunctional workers

• General purpose machines

• Study operators & improve operations

22

Flexible Resources

Page 12: LESSON 24: JUST-IN-TIME

23

Flexible Resources

Worker 1 Worker 2

Worker 3

Cell 1

Cell 5Cell 3

Cell 2

Cell 4

24

Pull Production System

• In a push system, a schedule is prepared in advance and as soon as one process completes its work, its products are sent to the next process.

• In a pull system, workers take the parts or materials from the preceding stations as needed.Workers at the preceding stations may produce the next unit only after their outputs are taken by the workers in the subsequent processes.

• Although the concept of pull production seems simple, it can be difficult to implement. Kanbans are introduced to implement the pull system.

Page 13: LESSON 24: JUST-IN-TIME

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Kanban Production Control

• A kanban is a card that indicates quantity of production

• Kanbans maintain the discipline of pull production– - A production kanban authorizes production– - A withdrawal kanban authorizes the movement of

goods

MachiningM-2

AssemblyA-4

Part no.: 7412Description: Slip rings

From : To:

Box capacity 25

Box Type A

Issue No. 3/5

26

The Origin Of Kanban

Q = order quantityR = reorder point

= demand during lead time

Bin 1 Bin 2

Q - RR

Reorder Card

Kanban

a. Two-bin inventory system b. Kanban Inventory System

Page 14: LESSON 24: JUST-IN-TIME

27

A Single-Kanban System

28

A Single-Card Kanban System

Consider the fabrication cell that feeds two assembly lines.1. As an assembly line needs more parts, the kanban card

for those parts is taken to the receiving post and a full container of parts is removed from the storage area.

2. The receiving post accumulates cards for both assembly lines and sequences the production of replenishment parts.

Page 15: LESSON 24: JUST-IN-TIME

29

A Dual Kanban System

30

1. When the number of tickets on the withdrawal kanban reaches a predetermined level, a worker takes these tickets to the store location.

2. The workers compares the part number on the production ordering kanban at the store with the part number on the withdrawal kanban.

3. The worker removes the production ordering kanban from the containers, places them on the production ordering kanban post, and places the withdrawal kanbans in the containers.

4. When a specified number of production ordering kanbans have accumulated, work center 1 proceeds with production.

A Two-Card System

Page 16: LESSON 24: JUST-IN-TIME

31

5. The worker transports parts picked up at the store to work center 2 and places them in a holding area until they are required for production.

6. When the parts enter production at work center 2, the worker removes the withdrawal kanbans and places them on the withdrawal kanban post.

Kanban Squares

X X X

XXX

Flow of workFlow of information

Page 17: LESSON 24: JUST-IN-TIME

Kanban Racks

407 409 410 412

408

411

Signal Kanban

407

408

409

407 408 409

Page 18: LESSON 24: JUST-IN-TIME

Kanban Post Office

65 66 67 68 69 70 71

72 73 74 75 76 77 78

79 80 81 82 83 84 85

86 87 88 89 90 91 92

93 94 95 96 97 98 99

100 101 102 103 104 105 106

Types Of Kanbans

• Kanban Square– marked area designed to hold items

• Signal Kanban– triangular kanban used to signal production at the

previous workstation• Material Kanban

– used to order material in advance of a process• Supplier Kanban

– rotates between the factory and supplier

Page 19: LESSON 24: JUST-IN-TIME

Determining Number Of Kanbans

where– y = number of kanbans or containers– = average demand over some time period– L = lead time to produce parts– w = safety stock, usually 10% of the demand during

lead time– a = container size

avg.demand during lead time + safety stockcontainer size

No. of kanbans =

awLD

y+

=

D

Kanban Calculation Example

Problem statement:= 150 bottles per hour L = 30 minutes = 0.5 hours

= (150)(0.5) = 75 w = 10% of a = 25 bottles

Solution:

Round up to 4 (allow some slack) or down to 3 (force improvement)

D

LDLD

containers Kanban .))(.(

3325

751075=

+=

+=

awLD

y

Page 20: LESSON 24: JUST-IN-TIME

39

Small-Lot Production

• Requires less space & capital investment

• Moves processes closer together

• Makes quality problems easier to detect

• Makes processes more dependent on each other

40

Small-lot Production

and Purchase

Page 21: LESSON 24: JUST-IN-TIME

41

Reducing Setup Time

• Preset desired settings

• Use quick fasteners• Use locator pins• Prevent

misalignments• Eliminate tools• Make movements

easier

42

Trends In Supplier Policies

1. Locate near to the customer2. Use small, side loaded trucks and ship mixed loads3. Consider establishing small warehouses near to the

customer or consolidating warehouses with other suppliers4. Use standardized containers and make deliveries according

to a precise delivery schedule5. Become a certified supplier and accept payment at regular

intervals rather than upon delivery

Page 22: LESSON 24: JUST-IN-TIME

43

Benefits Of JIT

1. Reduced inventory2. Improved quality3. Lower costs4. Reduced space

requirements5. Shorter lead time6. Increased productivity

7. Greater flexibility8. Better relations with

suppliers9. Simplified scheduling

and control activities10. Increased capacity11. Better use of human

resources12. More product variety

44

READING AND EXERCISES

Lesson 24Reading: Section 7.6 pp. 387-395 (4th Ed.) pp. 377-384

(5th Ed.)Exercise: 37 p. 395 (4th Ed.), p. 384 (5th Ed.)