lean manufacturing .H.Badkook

Lean manufacturing, sản xuất

lean manufacturing system

Toyota Production systems

( TPS )

Prepared by : Hassan Omar Badkook

2009

What is lean manufacturing?

Definitions :

► LM is a set of tools and methodologies that aims for the continuous

elimination of all waste in the production process.

► a system approach to identifying and eliminating waste (non-value added activities) through continuous improvement by flowing the product at the pull of the customer in pursuit of perfection

- The main benefits of LM are lower production costs , increased output and shorterproduction lead times

Key principles of lean manufacturing

1- Recognition of waste:

- The first step is to recognize what does and does not create value from the

customer’s perspective.

- Any material , process or feature which is not required for creating value from the

customer’s perspective is waste and should be eliminated

2- Standard processes :

- Lean requires an the implementation of very detailed production guidelines, called

(standard work)

- Clearly state the content , sequence , timing and outcome of all actions by workers.

- This eliminate variation in the way that workers perform their tasks

3- continuous flow :

- Lean aims to a continuous production flow free of bottlenecks, interruption

,backflows or waiting.

- Production cycle time can be reduced by as much as 90%

4- pull-production( also called Just-in-time)

- Aims to produce only what is needed , when it is needed.

- Production is pulled by the downstream workstation so that each workstation should only produce what is requested by the next workstation.

Key principles of lean manufacturing

5- Quality at source:

- lean aims for

- Defects to be eliminated at the source

- Quality inspection to be done by the workers as part of the in-line production process.

History of lean manufacturing

Key implications of lean manufacturing

Lean manufacturing

Traditional batch manufacturing

Customer driven Supply driven

Orientation

Orders are pulled through factory based on customer/downstream demand

Orders are pushed through factory based on production plan/forecast

Planning

Small large

Batch size

In-line inspection by workers

Checking of samples by QC inspectors

Quality inspection

Little or no work-in-progress between each production stage

Buffer of work-in-progress between each production stage

Handoff of works-in-process

Total production cycle shortens to approach time spent actually processing the materials

Total production cycle takes significantly longer than actual time spent processing the materials

Production cycle time

Lean manufacturing goals

lead times

Main kinds of waste

►Originally 7 main types of waste were identified as part of the Toyota

Production System.

►This list has been modified and expanded by various practitioners of lean manufacturing and generally includes the following :

1- Over-production waste:

▪ Unnecessarily producing more than demanded

▪ Producing it too early before it is needed

That will be:

- Increase the risk of obsolescence

- Increase the risk of producing the wrong thing

- Increases the possibility of having to sell those items at a discount or discard them asscrap

Main kinds of waste

2 - Waiting waste:

▪ Waiting is idle time for workers or machines due to bottlenecks or inefficient

production flow on the factory floor

▪ Waiting also includes small delays between processing of units

Waiting results in a significant cost insofar as it increases labor costs and

depreciation costs per unit of output

Transportation between processing stages results in prolonging

production cycle times , the inefficient use of labor and space and can also be a

source minor production stoppages

Main kinds of waste

- Include walking around the factory floor to look for a tool

- Difficult physical movements, due to poorly designed ergonomics which slowdown the workers

Main kinds of waste

▪ Production to incorrect specifications.

▪ Use of too much raw materials or generation of unnecessary scrap.

Main kinds of waste

8- Correction waste:

▪ When something has to be re-done because it wasn't done correctly the first time

▪ This not only results in inefficient use of labor and equipment but the act of

reprocessing often causes disruptions to the smooth flow of production and

therefore generates bottlenecks and stoppages

▪ Also, issues associated with reworking typically consume a significant amount ofmanagement time and therefore add to factory overhead costs

9- Knowledge disconnection:

▪ This is when information or knowledge isn't available where or when it is needed

▪ This might include information on correct procedures, specifications, ways to solveproblems, etc

▪ Lack of correct information often leads to defects and bottlenecks

▪ For example, unavailability of a mixing formula may potentially suspend the entireprocess or create defective items due to time- consuming trial-and-error tests

JIT/Lean production

Just-in-time

- A highly coordinated production system in which processing and

movement of materials and goods occur just as they are needed (perfect timing), usually in small batches.

- Developed in Toyota® by Taiichi Ohno (Vice president of

manufacturing) in the so-called Toyota Production System (TPS).

- JIT is characteristic of lean production systems where JIT operates with very little “fat”

Example : JIT at Hewlett-Packard

How much JIT reduced waste at Hewlett-Packard®

Scrap Setup Time

JIT/lean streamlines production

Flow with JIT

Traditional Flow

Customers Suppliers

Customers Suppliers

Production Process (stream of water)

Inventory (stagnant

(becomes like water in stream)

Lean manufacturing tools and methodology

►Standard work

►Communication of standard work to employees

►Standard work and flexibility

►Visual Management

►Quality and the source ( or “ Do it right the first time”)

►Value Stream Mapping

►The Five S’s

►Preventive Maintenance

►Total Productive Maintenance

►Changeover/setup time

►Batch size reduction

►Production Layout and point of use storage

Lean/JIT Goals and Building Blocks

Lean/JIT Building Blocks

1- product design

►standard parts

- use of standard parts leads to :

fewer parts - reduced training time and costs - routine purchasing and handling - low quality costs

1.1 standardized parts

1.2 modular design

Design modular components that can be configured into a wide variety

of end products and services

Modular Drills

1.3 quality in design

Quality function deployment (QFD) and House of quality

Voice of the customer)(

THE HOUSE OF QUALITY

X X

X

X X

Correlation:

Strong positive Positive Negative Strong negative

B A X

BA

X B

A X

B X A BXA BAX

1.4 concurrent engineering

2 - Process design

►small batch size

►setup time reduction

2.1 small batch size

Small lots also increase flexibility to meet

customer demands

Benefits of small lot size:

orders 10 Lot size = 5 & number of lots = 2 Lot 1 Lot 2

Lot size = 2 & number of lots = 5

Lot 1 Lot 2 Lot 3 Lot 4 Lot 5 Reducing Lot Sizes Increases the Number of Lots

Lot size = 10

Number of lots = 1

Small lot sizes

Effect of small lot sizes

Smaller Lot Size

TC

min

Optimal lot size

Small lots sizes increases inventory cost !

How this problem could beresolved ?

Unless setup costs are simultaneously reduced

New optimal lot size

Average inventory = (Lot size)/2

Effect of small lot sizes

Small lot sizes with frequent orders can reduce average inventory

Q2 when average order size=80,

average inventory is 40

Q1 when average order size=200,

average inventory is 100

2.2 Setup Reduction

►small lots leads to frequent setups.

►setups should be quick and inexpensive

►short setup require holding less inventory

►worker should be trained to their own setups

►use of standard (modular) fixtures for many type of parts

Standard and modular fixtures

Setup Reduction

SMED ( Single Minute Exchange Die )

►the concept arose in the late 1950s and early 1960s , when shigeo shingo , chiefengineer of Toyota, was contemplating Toyota’s inability to construct vehicles inmaximally efficient economic lots

►reduced setups – quick change over

Example: use of interrupted

screw , shigeo shingo

Setup Reduction steps by shigeo shingo

shigeo shingo recognizes 8 techniques that should be consider

in implementing SMED.

1- separate internal from external setup operations

2- convert internal to external setup

3- standardize function , not shape

4- use functional clamps or eliminate fasteners altogether

5- use intermediate jigs

6- adopt parallel operations

7- eliminate adjustments

8- mechanization

SMED / Quick Changeovers

Quick Changeover is a method of analyzing and reducing the time needed tochange a process from producing one good part to producing the next good part

Benefits of setup reduction / quick changeover techniques

Setup Reduction – Example by shigeo shingo

Machine Starts production

Changeover Time

2.3 Manufacturing cells

►JIT Objectives : reduce movement of people and material

( movement is waste!)

►JIT requires :

▪ Use work cell for product families

▪ Moveable or changeable machines

▪ Short distances

▪ Improve employee communication

▪ Little space for inventory

▪ Delivery directly to work areas

▪ Use Poka -Yoke devices

Poka – Yoke : fail – safe tools and methods to prevent mistakes

Classification of products into families and

manufacturing cells

Products into families

Work cell Vs process layout

Saw

Lathe Grinder

Heat Treat

Lathe

Lathe

Heat Treat

Grinder

Grinder Press

1 2

3

4 5

2

6

Saw

Press

input

IN

OUTTPS : Toyota Production System

2-5-Quality Improvement

►Occurrence of quality defects during the process can disrupt the orderly flow of work.

►Problem solving is important when defects occur.

►Never ending quest for quality improvement.

►focus on finding causes of problems.

Poka – yoke

Example: One way

to assemble the two

components together

www.campbell.berry.edu/pokayoke

2.6 production flexibility

►JIT Objective :

- Achieve the ability to process mix of products in a smooth flow

►Obstacle to do that:

- Bottlenecks due to overloads resulted from manufacturing some products

►Guidelines to increase flexibility in JIT:

- Reduce downtime due to changeovers by reducing changeover time

- Use preventive maintenance to reduce breakdowns

- Use many small capacities ( easier to shift capacity than small large capacities)

- Cross-train worker to help clear bottlenecks

- Use off-line buffers ( safety stock away from the production area)

- Reserve capacity for important customers

2.6 Inventory Storage

►Traditional : Inventory exists in case problems arise

►JIT objective : Eliminate inventory by eliminating problems before they

happen

►JIT inventory goal: Only have the minimum inventory needed to keep

system running

►Tactics :

- Use a pull system to reduce inventory

- Develop just-in-time delivery systems with suppliers

- Deliver directly to point of use no storage

- Perform – to – schedule

- Use group technology

Inventory is an Asset or Evil !

►lower inventory level ( sea water level )

Uncover hidden problems (Rocks)

Effect of inventory levels

Scrap

Work in process inventory level (hides problems)

High water level (inventory) hides rocks (problem)

Effect of inventory levels

Scrap

.

A lower water level ( inventory ) Uncover rocks ( problem) ROCKS (problem)- Late deliveries

- process downtime

- Bottlenecks

- Poor quality

- waste

3.Personal / organization elements

►worker as assets

►cross-trained workers

►continuous improvement

- kaizen : continuous improvement

- Andon : system of lights used at each workstation to signal problems or

slowdowns

►cost accounting

- activity-based costing:

▪ allocation of overhead to specific jobs based on their % activities

►leadership/ project management

Maximum height before Kaizen

Maximum height after Kaizen

Production methods & Kaizen

Layout before Kaizen

Layout after kaizen

Change-better

4 Manufacturing planning and control

►Level capacity loading

►Use pull systems

►Use visual systems

►Keep close vendor ( supplier ) relationships

►Reduce transaction processing

►Apply preventive maintenance

Andon Board

Green light – Normal operationYellow light – Assistance neededRed light – Line has been stopped

4.1 level capacity loading

►JIT focuses on achieving stable , smooth production with leveled daily mixed-model schedule

Given : Daily quantity requirements of different models

JIT requires to determine :

►sequencing

►number of cycles per day

►use of small lots

►number of units per cycle for each model

Assume the system is required to process 4 models

(A,B,C,D)

D C

B A

Model

45 50

120 100

Daily Quantity

Let the sequence is ( A-B-C-D)

Assume number of cycles = 20 cycles /day

D C

B A

Model

45 50

120 100

Daily quantity

1 3

6 5

Number of units per cycle

15 10

0 0

Extra units (inventory)

What if :

- Number of cycles = 25 or 22 or 23 ?

- Daily quantity has changed by 10 % ? Can you do any better ?

4.2 pull /push systems

- system for moving work where output is pushed to

the next station as it is completed

Push and pull systems

Station 1 Station 2 Station 3 Station 4 Station 5

►parts enter the system from one side and exits from the other side

►when station finishes the part, it pushes it to the next workstation

irrespective is that station free ( idle, or blocked )

►if, for example , T3<T4, parts will begin to build up causing station 4

to be blocked as time passes

Push and pull systems

Station 1 Station2Order part production from station 1 (POK)Station 3 Station 4 Station 5

Order part Retrieval from station 1 (WLK)

ProductionKANBAN

RetrievalKANBANPart processing time = Ti

PULL SYSTEM

►to prevent blocking , the successor station requests parts from the

predecessor station The predecessor station starts processing based on

that order the order is called a production ( Kanban ) ( POK ) After

processing the part, it may be ordered to move to the successor station by a

Retrieval Kanban ( WLK )

Pull system example

4.3 Visual systems (KANBAN)

erialscard or other device that communicates demand for worker or mat

KANBAN:

►

from the preceding station

►KANBAN is the Japanese word meaning “signal” or “visible record

►Paperless production control system

►Authority to pull, or produce comes from a downstream process

Kanban System

4.4 traditional and tiered supplier network

►suppliers do not cooperate

►each works directly with the company

►supplier have no motivation for improvement

►no distribution of responsibility

Traditional

Tiered supplier network

First Tier Supplier

Second Tier Supplier

Third Tier Supplier

Tiered

What a tiered system would provide ?

4.5 reduce transaction processing

4.6 preventive maintenance

►maintaining equipment in good operating conditions

►replacing parts that have tendency to fail before they actually fail

►housekeeping

▪ maintaining a workplace that is clean and free of unnecessary materials

5 S’s ( workplace organization )

Self discipline

Sort

StraightenSweep

Standardize

Clean machines,

floors, walls ,and

looking for sources

Keep everything that is needed in

an orderly fashion

so that things can

be accessed easily

Example : good housekeeping

www archive official-documents co uk

Standardized Work

Establishing precise procedures for

each operator’s work in a production

process, based on three elements:

products must be made in a process

in order to meet customer demand

2 The precise work sequence, in which

an operator performs tasks within

takt time

3 The standard inventory, including

units in machines, required to keep

the process operating smoothly

Standard Work Board