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Outline

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

LESSON 24: JUST-IN-TIME

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• Producing only what is needed and when it is needed

• A philosophy

• An integrated management system

Just-in-time

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• 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

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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

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Some Elements Of JIT

1. Focused factory networks 2. Grouped Technology: Cellular layouts 3. Quality at the source

4. Flexible resources5. Pull production system6. Kanban production control7. Small-lot production and purchase8. Quick setups9. Supplier networks

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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

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Cellular Layouts

Enter

Worker 1

Worker 2Worker

3

Exit

Key: Product routeWorker route

Machines

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Original Process Layout

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1

2

3

4

5

6 7

8

9

10

11

A B C Raw materials

Assembly

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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

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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

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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

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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

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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

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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

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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

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Cellular Layout Solution

12

12 3

4

5

6

7

8 910

11

A BCRaw materials

Cell1 Cell 2 Cell 3

Assembly

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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

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Disadvantages of Cellular Layouts

• Inadequate part families

• Poorly balanced cells

• Expanded training and scheduling of workers

• Increased capital investment

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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

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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

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Flexible Resources

• Multifunctional workers

• General purpose machines

• Study operators & improve operations

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Flexible Resources

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Flexible Resources

Worker 1 Worker 2

Worker 3

Cell 1

Cell 5Cell 3

Cell 2

Cell 4

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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.

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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

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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

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A Single-Kanban System

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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.

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A Dual Kanban System

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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

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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

XX

X

Flow of workFlow of information

Kanban Racks

407 409 410 412

408

411

Signal Kanban

407

408

409

407 408 409

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

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 =

a

wLDy

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

a

wLDy

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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

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Small-lot Production

and Purchase

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Reducing Setup Time

• Preset desired settings

• Use quick fasteners• Use locator pins• Prevent

misalignments• Eliminate tools• Make movements

easier

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Trends In Supplier Policies

1. Locate near to the customer

2. Use small, side loaded trucks and ship mixed loads

3. Consider establishing small warehouses near to the customer or consolidating warehouses with other suppliers

4. Use standardized containers and make deliveries according to a precise delivery schedule

5. Become a certified supplier and accept payment at regular intervals rather than upon delivery

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Benefits Of JIT

1. Reduced inventory

2. Improved quality

3. Lower costs

4. Reduced space requirements

5. Shorter lead time

6. Increased productivity

7. Greater flexibility

8. Better relations with suppliers

9. Simplified scheduling and control activities

10. Increased capacity

11. Better use of human resources

12. More product variety

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READING AND EXERCISES

Lesson 24

Reading: Section 7.6 pp. 387-395 (4th Ed.) pp. 377-384 (5th Ed.)

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