PowerPoint Presentations 17

Report
17.1
Chapter 17
Quality management
Pearson Education Ltd. Naki Kouyioumtzis
17.1
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
17.2
Capacity planning and control
Operations
strategy
Design
Quality
management
Improvement
Planning and
control
The market requires…
consistent quality of
products and services
The operation supplies…
the consistent delivery of
products and services at
specification or above
17.2
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
17.3
Key operations questions
In Chapter 17 – Quality planning and control – Slack et al.
identify the following key questions:
• What is quality and why is it so important?
• How can quality problems be diagnosed?
• What steps lead towards conformance to specification?
• What is Total Quality Management (TQM)?
17.3
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
17.4
High quality puts costs down and revenue up
Quality up
Rework and
scrap costs
down
Image up
Service
costs down
Inventory
down
Inspection
and test
costs down
Sales
volume up
Price
competition
down
Processing
time down
Complaint and
warranty costs
down
Scale
economies up
Capital
costs down
Productivity
up
Operation
costs down
Revenue
up
Profits up
17.4
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
17.5
Perceived quality is governed by the gap between customers’
expectations and their perceptions of the product or service
Gap
Customers’
expectations
for the
Customers’
product or
perceptions
service
of the
product or
service
Expectations >
perceptions
Perceived quality is
poor
17.5
Gap
Customers’ Customers’
expectations perceptions
of the
for the
product or
product or
service
service
Expectations =
perceptions
Perceived quality is
acceptable
Customers’
expectations
for the
product or
service
Customers’
perceptions
of the
product or
service
Expectations <
perceptions
Perceived quality is
good
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
17.6
A ‘Gap’ model of Quality
Word of mouth
communications
Previous
Experience
Image of product
or service
Customers’
expectations
concerning a
product or service
The
customer’s
domain
Gap ?
Customers’
perceptions
concerning the
product or service
Gap 4
Customers’ own
specification of
quality
Gap 1
Management’s
concept of the
product or service
The actual product
or service
Organization’s
specification of
quality
Gap 3
Gap 2
17.6
The operation’s domain
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
17.7
17.7
The perception – expectation gap
Gap
Action required to ensure high
perceived quality
Main organizational
responsibility
Gap 1
Ensure consistency between internal
quality specification and the
expectations of customers
Marketing, operations,
product/service
development
Gap 2
Ensure internal specification meets
its intended concept of design
Marketing, operations,
product/service
development
Gap 3
Ensure actual product or service
conforms to internally specified
quality level
Operations
Gap 4
Ensure that promises made to
customers concerning the product or
service can really be delivered
Marketing
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
17.8
Quality characteristics of goods and services
Functionality – how well the product or service does the
job for which it was intended.
Appearance – aesthetic appeal, look, feel, sound and
smell of the product or service.
Reliability – consistency of product or services
performance over time.
Durability – the total useful life of the product or service.
Recovery – the ease with which problems with the
product or service can be rectified or resolved.
Contact – the nature of the person-to-person
contacts that take place.
17.8
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
17.9
Attribute and variable measures of quality
Attributes
Variables
Defective or not defective?
17.9
Measured on a
continuous scale
Light bulb works or
does not work?
Light emission of
bulb
Number of defects in a
. blade
turbine
Length of blade
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
17.10
Aspects of quality
Quality
Quality
fitness for purpose
Quality of Design
degree to which
design achieves purpose
Quality of Conformance
faithfulness with which the
operation agrees with design
Variables
things you can measure
17.10
Reliability
ability to continue
working at accepted
quality level
Attributes
things you can assess
accept/reject
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
17.11
Total Quality Management
What does Total Quality Management include?
• Includes all parts of the organization
• Includes all staff of the organization
• Includes consideration of all costs
• Includes every opportunity to get things right
• Includes all the systems that affect quality
• And it never stops!
17.11
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
17.12
Total quality management can be viewed as a natural extension
of earlier approaches to quality management
•
•
•
•
Makes quality
central and strategic
in the organization
•
•
•
•
Broadens the
organizational
responsibility for quality
Solves the root
cause of quality
problems
Prevents ‘out of
specification’ products and
services reaching market
Quality systems
Quality costing
Problem solving
Quality planning
• Statistics
• Process analysis
• Quality standards
• Error
detection
• Rectification
Inspection
17.12
Quality is strategic
Teamwork
Staff empowerment
Involves customers and suppliers
Quality
control
Quality
assurance
Total Quality
Management
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
17.13
The internal customer–supplier concept involves
understanding the relationship between processes
Process
3
External
supplier
Process
1
Process
6
Process
2
External
customer
Process
5
Process
4
17.13
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
The traditional cost of quality model
Costs
17.14
‘Optimum’ amount of
quality effort
Amount of quality effort
Cost of errors = costs
of prevention and
appraisal
17.14
Total cost of
quality
Cost of quality provision =
costs of internal and
external failure
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
The traditional cost of quality model with adjustments
to reflect TQM criticisms
Costs
17.15
‘Optimum’ amount
of quality effort
Amount of quality effort
Cost of errors = costs
of prevention and
appraisal
17.15
Total cost of
quality
Cost of quality provision =
costs of internal and
external failure
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
17.16
EFQM ‘Business excellence’ model
People
results
People
Leadership
Policy and
strategy
Processes
Partnerships
and resources
17.16
Customer
results
Key
performance
results
Society
results
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
17.17
17.17
The quality gurus
Philip Crosby
Quality is free – the optimum is zero
defects
W. Edwards Deming
Deming’s 14 points
How to use statistics
Armand Feigenbaum
Total quality control
Kaoru Ishikawa
Quality circles and cause and effect
diagrams
Joseph Juran
Quality as fitness for use, rather than
conformance to specification
Genichi Taguchi
Loss function
Minimize variation
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
17.18
The cost of rectifying errors becomes increasingly expensive the longer
the errors remain uncorrected in the development and launch process
Cost to rectify error
10, 000
1000
100
10
1
Concept
Design
Prototype
Pilot
Market use
production
Stage in the development and launch process
17.18
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
17.19
Increasing the effort spent on preventing errors occurring in the first
place brings a more than equivalent reduction in other cost categories
Total cost of quality
Costs of quality
Appraisal
Internal failure
Appraisal
Prevention
Time
17.19
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
The pattern of some TQM programmes which run out of
enthusiasm
Effectiveness of the TQM initiative
17.20
17.20
Introduction
Growth
Levelling off
Disillusionment
Repackaging
Learning and
understanding
Increasing
enthusiasm
Starting to hit the
more difficult
problems
Waning
enthusiasm
Attempts to
revitalize the
programme
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
17.21
Process control charting
Some aspect of the performance of a process is often
measured over time.
Some measure of
operations performance
Question
‘Why do we do this?’
Time
17.21
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
17.22
Process control charting (Continued)
Trend can indicate whether performance is getting
better or worse
Some measure of
operations performance
Question
‘But why is variation important?’
Time
17.22
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
17.23
Process control charting (Continued)
The last point plotted on this chart seems to be unusually low.
How do we know if this is just random variation or the result of
some change in the process which we should investigate?
Some measure of
operations performance
Some kind of ‘Guide lines’ or ‘Control limits’ would be useful.
Time
17.23
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
17.24
Process control charting (Continued)
Sampling over a period of time…
0.8
2.2
3.6
After the first
sample
2.2
0.8
3.6
After the second
sample
2.2
3.6
Fitting a normal
distribution to the
histogram of sampled
call times
0.8
0.8
17.24
2.2
3.6
By the end of the
day
0.8
2.2
3.6
By the end of the
second day
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
17.25
The chances of measurement points deviating from the
average is predictable
in a control
normal charting
distribution
Process
99.7% of points
–3 standard
deviations
+3 standard
deviations
–2 standard
deviations
95.4% of points
Frequency
–1 standard
deviation
+2 standard
deviations
+1 standard
deviation
68% of points
A standard
deviation
S=
sigma
40
100
160
Elapsed time of call (seconds)
17.25
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
17.26
Process control charting
If we understand the normal distribution which describes
random variation when the process is operating normally, then,
we can use the distribution to draw the control limits.
Some measure of
operations performance
In this case, the final point is very likely to be caused by an
‘assignable’ cause, i.e. the process is likely to be out of control.
Time
17.26
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
17.27
Process variability
AP
X
AX
P
Off target ACCURACY : P
Scatter
PRECISION : P
AX
P
X
17.27
AP
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
Low process variation allows changes in process
performance to be readily detected
17.28
Process
distribution A
A
A
B
B
TIME
17.28
Process
distribution A
Process
distribution B
Process
distribution B
TIME
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
17.29
In addition to points falling outside the control limits other
unlikely sequences of points should be investigated
UCL
C/L
LCL
Alternating and erratic behaviour – Investigate.
17.29
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
17.30
In addition to points falling outside the control limits other
unlikely sequences of points should be investigated (Continued)
UCL
C/L
LCL
Suspiciously average behaviour – Investigate.
17.30
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
17.31
In addition to points falling outside the control limits other unlikely
sequences of points should be investigated (Continued)
UCL
C/L
LCL
Two points near control limit – Investigate.
17.31
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
17.32
In addition to points falling outside the control limits other
unlikely sequences of points should be investigated (Continued)
UCL
C/L
LCL
Five points one side of centre line – Investigate.
17.32
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
17.33
In addition to points falling outside the control limits other
unlikely sequences of points should be investigated (Continued)
UCL
C/L
LCL
Apparent trend in one direction – Investigate.
17.33
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
17.34
In addition to points falling outside the control limits other
unlikely sequences of points should be investigated (Continued)
UCL
C/L
LCL
Sudden change in level – Investigate.
17.34
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
Process variation and its effect on process Defects per
Million Opportunities (DPMO)
17.35
Process
variation
LSL
17.35
Process
variation
USL LSL
USL
Process
variation
LSL
Process
variation
USL LSL
USL
3 sigma process
variation
4 sigma process
variation
5 sigma process
variation
6 sigma process
variation
= 66,800 Defects
per million
opportunities
= 6200 Defects
per million
opportunities
= 230 Defects per
million
opportunities
= 3.4 Defects per
million
opportunities
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
17.36
Ideal and real operating characteristics
In this ideal operating characteristic, the
probability of accepting the batch if it
contains more than 0.04% defective
items is zero, and the probability of
accepting the batch if it contains less than
0.04% items defective is 1.
Producer’s risk (0.05)
Probability of accepting the batch
1.0
0.9
0.8
0.7
In this real operating characteristic
(where n = 250 and c = 1), both
type 1 and type 2 errors will occur.
0.6
0.5
0.4
Type 1 error
0.3
Type 2 error
0.2
0.1
AQL
Consumer’s risk (1.0)
LTPD
0
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
Percentage actual defective in the batch
17.36
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010

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