9) Just in Time

(1)

TI-3122

Perencanaan dan Pengendalian Produksi

Just In Time

Laboratorium Sistem Produksi www.lspitb.org

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

(2)

TI3122-Perencanaan dan Pengendalian Produksi - Minggu 9 3

Relative Performance in Auto Industry

Toyota Japan (average) USA (average) Europe (average)

Deliveries

(percent late)

1st-tier suppliers 2nd-tier suppliers 0.04 0.5 0.2 2.6 0.6 13.4 1.9 5.4

Stocks

(1st-tier suppliers)

Hours

Stock turns (per year)

Na 248 37 81 135 69 138 45

1993-94, from Womack and Jones, Lean Thinking

Relative Performance in Auto Industry

Toyota Japan (average) USA (average) Europe (average)

Productivity

Assembly 1st-tier suppliers 100 100 83 85 65 71 54 62

Quality

(delivered defects)

Assembly (per 100 cars) 1st-tier suppliers (PPM) 2nd-tier suppliers (PPM) 30 5 400 55 193 900 61 263 6100 61 1373 4723

(3)

Hewlett Packard’s Cupertino

California plant

1982 (before JIT) 1986 (after JIT) 15 days 11.3 hours $670,000 $20,000 lead time work in process no. of back orders 200 2

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

(4)

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

United States of America Japan

Market Research Market Research

Product Characteristics Product Characteristic Design Planned selling price – desired profit

Engineering Target Cost

Supplier pricing Design Engineering Supplier pricing Cost

(5)

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

ジャストインタイム Just in time 標準作業 Stand. oper. 平準化 level prod 流産業 Flow mfg 現場改善の基礎 Workplace improvement, 5 S 少人化 Manpower reduction 目で見る管理 Visual management 保全・安全自働化段取り替え多工程持ち品質保証かんばん Jidoka Change-over Multiprocess handling Maintenance & safety Quality assurance Kanban

(6)

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

The 5S’s Principle

•

Seiri

putting things in order

distinguishing between the necessary and the unnecessary

getting rid of the unnecessary

(7)

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

The 5S’s Principle

•

Shitsuke

doing the right thing as a matter of course

(8)

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

Inventory Hides Problems

Poor Quality Unreliable Supplier Machine Breakdown Inefficient Layout Bad Design Lengthy Setups

(9)

Lower Levels of Inventory to Expose Problems

Poor Quality Unreliable Supplier Machine Breakdown Inefficient Layout Bad Design Lengthy Setups

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

(10)

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

Push and Pull Systems

(11)

Push and Pull Systems

•

Pull system

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

(12)

Samples Kanban

(13)

TI3122-Perencanaan dan Pengendalian Produksi - Minggu 9 25 Machining M-2 Assembly A-4 Part no.: 7412

Description: Slip rings

From : To:

Box capacity 25

Box Type A

Issue No. 3/5

Kanban System

(14)

Kanban System

•

Withdrawal Kanban

Dual Kanban Systems

(15)

Dual Kanbans

P

W _{Container with withdrawal kanban}

Container with production kanban

P W P X X X X X Flow of work Flow of kanban

Kanban Squares

X X _X

X X

(16)

Kanban Golden Rule

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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

Determining Number 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

No. of kanbans = mand during lead time + safety stock container size

average de

N dL S

C

(17)

Kanban Calculation Example

Problem statement:

d = 150 bottles per hour L = 30 minutes = 0.5 hours dL = (150)(0.5) = 75 S = 10% dL = 10% x 75 = 7.5 C = 25 bottles

Solution:

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

N dL S C x = + = + = + = ( . ) . . 150 0 5 7 5 25 75 7 5 25 3.3 kanbans or containers

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

(18)

Once a Month Production

Product

Week 1

Week 2

Week 3

Week 4

X (1000)

Y(600)

Z(400)

Once a Week Production

Product

Week 1

Week 2

Week 3

Week 4

X

250

250 Y

150

(19)

Once a Day Production

Product

Week 1

Week 2

Week 3

Week 4

X

50 units

a day

Y

30 units

a day

Z

20 units

a day

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

(20)

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

• 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

(21)

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

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

(22)

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

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

(23)

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

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)

(24)

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

Reasons for the accident occurrence

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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

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The equipment lacked an accident-prevention device

(25)

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

Visual Control

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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)?

•

What should be done? --- What are the

(26)

Visual Control Tools

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Make them easy to see from a distance

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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

Visual Control

Library shelf Work station Visual kanbans Tool board Machine controls 30-50 How to sensor