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LESSON 24: JUST-IN-TIME. Outline Just-in-Time (JIT) Examples of Waste Some Elements of JIT. Just-in-time. Producing only what is needed and when it is needed A philosophy An integrated management system. Just-in-time. Theme: eliminate all waste including the ones caused by: - PowerPoint PPT Presentation
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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
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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
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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.)