9) Just in Time
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Departemen Teknik Industri FTI-ITB
TI-3122 Perencanaan dan Pengendalian Produksi Just In Time
Laboratorium Sistem Produksi www.lspitb.org ©2003
Departemen Teknik Industri FTI-ITB
Hasil Pembelajaran •
Umum Mahasiswa mampu menerapkan model matematik, heuristik dan teknik statistik untuk menganalisis dan merancang suatu sistem perencanaan dan pengendalian produksi
•
Khusus Memahami konsep dan teknik dalam sistem produksi just in time
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Departemen Teknik Industri FTI-ITB
Relative Performance in Auto Industry Toyota Japan
Deliveries (percent late) 1st-tier suppliers 2nd-tier suppliers
Stocks (1 -tier suppliers)
USA
Europe
(average)
(average)
(average)
0.04 0.5
0.2 2.6
0.6 13.4
1.9 5.4
Na 248
37 81
135 69
138 45
st
Hours Stock turns (per year)
1993-94, from Womack and Jones, Lean Thinking 3
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Departemen Teknik Industri FTI-ITB
Relative Performance in Auto Industry Toyota Japan
Productivity Assembly 1st-tier suppliers
Quality (delivered defects)
100 100
Assembly (per 100 cars) 30 1st-tier suppliers (PPM) 5 2nd-tier suppliers (PPM) 400
USA
Europe
(average)
(average)
(average)
83 85
65 71
54 62
55 193 900
61 263 6100
61 1373 4723
1993-94, from Womack and Jones, Lean Thinking
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Departemen Teknik Industri FTI-ITB
Hewlett Packard’s Cupertino California plant 1982 (before JIT)
1986 (after JIT)
lead time
15 days
11.3 hours
work in process
$670,000
$20,000
no. of back orders
200
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Departemen Teknik Industri FTI-ITB
The Cost Subtraction Formula •
Cost + Profit = Selling Price there is no need for improvement there is no competing procedure consumer may have no choice
•
Profit = Selling Price – Cost the price is determined by the market profit is what remains after subtracting cost from price maximizing profit means that cost is to be minimized
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Departemen Teknik Industri FTI-ITB
The Cost Subtraction Formula •
Cost = Price – Profit setting a target cost the price is determined by the market profit required is determined by the company
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Departemen Teknik Industri FTI-ITB
United States of America Market Research Product Characteristics Design
Japan Market Research Product Characteristic Planned selling price – desired profit
Engineering Supplier pricing
Target Cost Design Engineering Supplier pricing
Cost Manufacturing Periodic cost reduction
Manufacturing Continuous cost reduction
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Departemen Teknik Industri FTI-ITB
Is JIT a Culture-based System? •
Schonberger, 1982, Japanese manufacturing techniques: Nine hidden Lessons in simplicity, Free Press, New York The forth lesson: Culture is no obstacle
•
Yoshiki Yamasaki (President of Toyo Kogyo) I would ask you never to be self-satisfied, but always to aim for a higher objective. No matter how hard you try, there is no victory if your competitors work harder. I would ask you to continue striving, not only to best the competition but also to keep on improving yourself
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ジャストインタイム Just in time Maintenance & safety
Stand. oper.
Changeover
Quality assurance
平準化
段取り 替え
level prod
Multiprocess handling 多工程 持ち
品質保 証 Kanban
流産業 Flow mfg
かん ばん
Visual management
Manpower reduction
少人化
保全・ 安全
標準 作業
自働化
目で見る管理
Jidoka
現場改善の基礎 Workplace improvement, 5 S
Introduction procedure
意義改革 Awareness revolution
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Departemen Teknik Industri FTI-ITB
The 5S’s Principle •
Seiri (整理)
=Organization (Proper arrangement)
•
Seiton(整頓)
=Neatness (Orderliness)
•
Seiso(清掃)
=Cleanliness
•
Seiketsu(清潔) =Standardization
•
Shitsuke(仕付け) =Discipline
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The 5S’s Principle •
Seiri putting things in order distinguishing between the necessary and the unnecessary getting rid of the unnecessary stratification management
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The 5S’s Principle •
Seiton having things in the right places/layout (eliminating searches) functional management
•
Seiso cleaning (is a form of inspection) eliminating waste
•
Seiketsu continually and repeatedly maintaining the above 3Ss visual management TI3122-Perencanaan dan Pengendalian Produksi - Minggu 9
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Departemen Teknik Industri FTI-ITB
The 5S’s Principle •
Shitsuke doing the right thing as a matter of course practicing good habit and discipline
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Flow Production • • • • •
Goods and material should flow in the factory much as water flows in a river But the river (the flow of in process inventory) tends to flood High water volume conceals the rocks/problems. Low water volume reveals the rocks /problems A factory needs to have a smooth flow of inventory and operations Japanese management tends to view inventory as the root of all evil and the likely cause of poor performance in any business activity
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Inventory Hides Problems
Bad Design Lengthy Setups Inefficient Layout
Poor Quality Machine Breakdown
Unreliable Supplier
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Lower Levels of Inventory to Expose Problems
Bad Design Lengthy Setups Inefficient Layout
Poor Quality Machine Breakdown
Unreliable Supplier
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Multi-process Operations •
• •
Productivity is important indeed but not as important as respecting the humanity of our workers. Productivity and humanity must coexist in the factory. The factory must find a way to satisfy both productivity and humanity People must be trained in the multiple skills to handle several processes The assignment where one worker handles 5 different machines/processes is better than the assignment where one worker handles 4 similar machines
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Multi-process Operations •
Key points:
Establish U shape manufacturing cells Abolish processing islands Make the equipment smaller Standing while working Multiple skills training Separate human work from machine work Human automation (jidoka, 自働化）and pokayoke Safety first
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Push and Pull Systems •
Push system
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Push and Pull Systems •
Pull system
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Departemen Teknik Industri FTI-ITB
Kanban System •
Kanban Card, label, signboard or visible representation The information system controlling the number of parts Synchronizing production lines and assembly lines
•
Types of Kanban: Production Kanban Withdrawal Kanban
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Samples Kanban
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Departemen Teknik Industri FTI-ITB
Part no.: 7412 Description: Slip rings
From : Machining M-2
Box capacity
25
Box Type
A
Issue No.
3/5
To: Assembly A-4
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Kanban System •
Production Kanban
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Kanban System •
Withdrawal Kanban
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Dual Kanban Systems •
Upstream and downstream operations
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Dual Kanbans P
W
X X X
P
X
X
W
Container with withdrawal kanban
Flow of work
P
Container with production kanban
Flow of kanban
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Departemen Teknik Industri FTI-ITB
Kanban Squares
X
X
X
X X
X
Flow of work Flow of information TI3122-Perencanaan dan Pengendalian Produksi - Minggu 9
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Departemen Teknik Industri FTI-ITB
Kanban Golden Rule • • • • • •
Do not move nonconforming parts to a downstream process Ensure that downstream processes withdraw parts from upstream processes in the correct quantity at the right time Do not let upstream processes produce more than the quantity of parts withdrawn by downstream processes Ensure that production is leveled Do not attempt to transmit large demand variation with the Kanban system Balance cycle times for smooth production, and constantly improve cells and workstations TI3122-Perencanaan dan Pengendalian Produksi - Minggu 9
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Departemen Teknik Industri FTI-ITB
Determining Number Of Kanbans average demand during lead time + safety stock container size dL + S N= C
No. of kanbans =
where N = number of kanbans or containers d = average demand over some time period L = lead time to produce parts S = safety stock C = container size TI3122-Perencanaan dan Pengendalian Produksi - Minggu 9
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Kanban Calculation Example Problem statement: d = 150 bottles per hour dL = (150)(0.5) = 75 C = 25 bottles
L = 30 minutes = 0.5 hours S = 10% dL = 10% x 75 = 7.5
Solution: dL + S (150 x0.5) + 7.5 = C 25 75 + 7.5 = = 3.3 kanbans or containers 25
N=
Round up to 4 (allow some slack) or down to 3 (force improvement)
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Level Production • • •
Making production of various product model and volume completely even Production scheduling methods: once a month production, once a week production, once a day production, and level production Suppose a factory should process the following products – Product X: 1000 units per month – Product Y: 600 units per month – Product Z: 400 units per month
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Once a Month Production Product X (1000) Y(600) Z(400)
Week 1
Week 2
Week 3
Week 4
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Once a Week Production Product X Y Z
Week 1 250 150 100
Week 2 250 150 100
Week 3 250 150 100
Week 4 250 150 100
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Once a Day Production Product X Y Z
Week 1
Week 2 50 units 30 units 20 units
Week 3 a day a day a day
Week 4
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Departemen Teknik Industri FTI-ITB
Leveling Production • Working minutes in day: 8 hours x 60 minutes = 480 • • •
minutes Product X: 480 minutes/50 units = 9.8 minutes per unit Product Y: 480 minutes/30 units = 16 minutes per unit Product Z: 480 minutes/20 units = 24 minutes per unit
• The number of products to be processed in day: (50+30+20) units
• Tact time (the time it takes to produce one piece of product): 480 minutes/100 units = 4.8 minutes
• X: 5 units; Y: 3 units; Z: 2 units ===== 10 units every 48 minutes
• Schedule: X-Y-X-Z-X-Y-X-Z-X-Y (repeated this sequence 10 times)
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Quality Assurance • • •
•
Quality assurance is the starting point in building products Elements where defects most often occur： Operator, material, machine, method, and information Overall plan for achieving zero defects – – – – – –
Operator: Basic training and multiple skills training Material: Preventive inspection Machine: Pokayoke and preventive maintenance Method: Flow production and standard operations Information: Visual control Basic strategy for zero defects: The 5S’s
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Pokayoke (Mistake-proofing) • The pokayoke system possesses two functions: it can carry out 100% inspections and, if abnormalities occurs, it can carry out immediate feed back and action:
When there is a working mistake, the material will not fit the tool If there is irregularity in the material, the machine will not start If there is a working mistake, the machine will not start the machining process When there are working mistakes or steps left out, corrections are made automatically and machining continues Irregularities in the earlier processes are checked in the later process to stop the defective products When a step is forgotten, the next process will not start
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Setup • • • • •
Shortening setup time could minimize lot sizes, therefore reduce the stock of intermediate and finished products Through small lot sizes, the manufacturing lead times (MLT) of various kinds of products (mixed scheduling) can be shortened Through short MLT, the company can adapt to customer orders and demand changes very promptly SMED (single minute exchange of dies) is not only a technique but also a concept. It was developed by Shigeo Shingo Single minute means that the setup should be performed within 9 minutes 59 seconds TI3122-Perencanaan dan Pengendalian Produksi - Minggu 9
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The Concept of SMED •
In order to shorten the setup time using SMED, there are 4 major concepts, and 6 techniques for applying the concepts
•
These concepts are: Separate the internal setup (requires that the machine be stopped) from the external setup (while the machine is operating) Convert as much as possible of the internal setup to the external setup Eliminate adjustment process Abolish the setup itself
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The Techniques of SMED •
The techniques are: Standardize the external setup actions: made into routines and standardize Standardize only the necessary portions of the machine: since it is very expensive Use a quick fastener: sliding guide block Use a supplementary tool: revolving table Use parallel operations Use a mechanical setup system: air or oil pressure
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Standard Operations •
•
• •
Standard operations is an effective combination of workers, materials and machines for the sake of making high quality products cheaply, quickly, and safely Basic elements of standard operations: – Cycle time – Work sequence – Standard in process inventory
The principles of motion economy and 3Ms are very useful tools for establishing improving standard operations 3M: Muda ( 無駄) or waste, Mura (斑) or inconsistency, and Muri (無理) or irrationality TI3122-Perencanaan dan Pengendalian Produksi - Minggu 9
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Departemen Teknik Industri FTI-ITB
JIDOKA •
•
Jidoka (自動化) means automation, i.e., a mechanism where the machine operates by itself once the switch is thrown but has no feedback control for detecting errors and no device for stopping the process if a malfunction occurs. Jidoka (自働化) means autonomation, i.e., a mechanism to detect abnormalities or defects and to stop the line or machine when abnormalities or defects occur
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Maintenance and Safety •
• •
Total productive maintenance (TPM) treating the causes of breakdowns before the breakdowns actually happen is the key to achieving zero breakdowns Accidents happen because of deterioration Stages on the path to breakdown: latent minor defects, apparent minor defects, performing below expectations, stops intermittently, and completely stop (breaks down)
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Maintenance •
• •
Four basic maintenance activity: – – – –
Maintenance prevention (MP) Preventive maintenance (PM) Corrective Maintenance (CM) Independent maintenance and improvement
The maintenance cycle: MP-PM-CM The CCO (cleanliness, checking and oiling) habit must be an integral part of the routine tasks
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Reasons for the accident occurrence • • • •
The worker was not adequately trained The safety saying was put into the book but not into the mind of the worker Safety has not been built into the operational procedure The equipment lacked an accident-prevention device
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Shojinka(少人化) •
•
Shojinka means to alter (decrease or increase) the number of workers at a shop when the production demand has changed (decrease or increase) The prerequisite for realizing shojinka: – Proper design of machinery layout (U-shaped layout) – Well-trained and multifunctional workers – Continuous evaluation and revision of the standard operations
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Visual Control •
What is being managed and where should people look? ---- What are the important points
•
What constitutes an abnormality ----- What are the standards?
•
It is discernible? ----- What are the tools used for inspection, and is the inspections easy to do (including easy of evaluation)?
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What should be done? ----- What are the emergency procedures and what are long term remedies? TI3122-Perencanaan dan Pengendalian Produksi - Minggu 9
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Departemen Teknik Industri FTI-ITB
Visual Control Tools • • • • • • •
Make them easy to see from a distance Put the displays on the things they are for Make them so that anyone can tell what is right and what is wrong Make them so that anybody can use them easily and conveniently Make them so that anybody can follow them and make them the necessary correction easily Make them so that using them makes the workplace brighter and more orderly Example: kanban/label, display, marks, andon, color TI3122-Perencanaan dan Pengendalian Produksi - Minggu 9
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Departemen Teknik Industri FTI-ITB
Visual Control Tool board
Visual kanbans
Work station
Library shelf
How to sensor
30-50
Machine controls
Good
Better
Best
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