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Chapter 4: Six Sigma for Process and Quality Improvement
1
Chapter 4
Six Sigma for Process and Quality Improvement
Chapter 4: Six Sigma for Process and Quality Improvement
2
Quality Management and Six Sigma in Perspective
Two primary sets of costs are involved in quality: control costs failure costs
Costs broken into four categories: Prevention costs Appraisal costs Internal costs of defects External costs of defects
Chapter 4: Six Sigma for Process and Quality Improvement
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Japanese Approaches to Quality
In 1950 the Japanese government invited W. Edwards Deming (then a professor at New York University) to give a series of lectures on quality control to help Japanese engineers reindustrialize the country.
Chapter 4: Six Sigma for Process and Quality Improvement
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W. Edwards Deming
Major source of poor quality is variation
Quality improvement the responsibility of top management
All employees should be trained in use of problem solving tools and especially statistical techniques
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Deming’s 14 Points
1. Create constancy of purpose
2. Adopt the new philosophy
3. Cease dependence on mass inspection
4. End practice of awarding business on basis of price tags
5. Improve constantly and forever
6. Institute modern methods of training
Chapter 4: Six Sigma for Process and Quality Improvement
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Deming’s 14 Points continued
7. Institute modern method of supervision
8. Drive out fear
9. Breakdown organizational barriers
10.Eliminate arbitrary numerical goals
11. Eliminate work standards and quotas
12.Remove barriers that reduce pride of workmanship
Chapter 4: Six Sigma for Process and Quality Improvement
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Deming’s 14 Points continued
13. Institute a vigorous program of education and training
14. Push the 13 points everyday
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Total Quality Management (TQM)
Better to produce item right the first time than to try to inspect quality in
Quality at the source - responsibility shifted from quality control department to workers
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History of TQM
Dr. Shewart began using statistical control at the Bell Institute in 1930s
Military standards developed in 1950s After World War II, Japanese Union of
Scientist and Engineers began consulting with Deming
Deming Prize introduced in Japan in 1951
Chapter 4: Six Sigma for Process and Quality Improvement
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History of TQM continued
Quality assurance concept proposed in 1952 Juran makes first trip to Japan in 1954 Quality becomes Japan’s national slogan in
1956 First quality circles created in 1957 10,000 quality circles by 1966 100,000 quality circles by 1977 First U.S. quality circle 1974
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Five Steps in TQM
Determine what customers want Develop products and services Develop production system Monitor the system Include customers and suppliers
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Joseph Juran
Quality Control Handbook (1951) Employees speak in different languages Quality Trilogy
Quality Planning Quality Control Quality Improvement
Need to place more emphasis on planning and improvement
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Joseph Juran continued
Organizations progress through four phases Minimize prevention and appraisal costs Appraisal costs increased Process control introduced increasing
appraisal costs but lowering internal and external failure costs
Prevention costs increased in effort to lower total quality costs
Chapter 4: Six Sigma for Process and Quality Improvement
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A Brief History of Six Sigma
The Six Sigma concept was developed by Bill Smith, a senior engineer at Motorola, in 1986 as a way to standardize the way defects were tallied.
Sigma is the Greek symbol used in statistics to refer to standard deviation which is a measure of variation.
Adding “six” to “sigma” combines a measure of process performance (sigma) with the goal of nearly perfect quality (six).
Chapter 4: Six Sigma for Process and Quality Improvement
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A Brief History of Six Sigma continued
In the popular book The Six Sigma Way, Six Sigma is defined as: a comprehensive and flexible system for
achieving, sustaining and maximizing business success. Six Sigma is uniquely driven by close understanding of customer needs, disciplined use of facts, data, and statistical analysis, and diligent attention to managing, improving, and reinventing business processes. (p. xi)
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The DMAIC Improvement Process
Six Sigma projects generally follow a well defined process consisting of five phases. define measure analyze improve control pronounced dey-MAY-ihk
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The DMAIC Improvement Process
Chapter 4: Six Sigma for Process and Quality Improvement
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Chapter 4: Six Sigma for Process and Quality Improvement
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The Define Phase
The define phase of a DMAIC project focuses on clearly specifying the problem or opportunity, what the goals are for the process improvement project, and what the scope of the project is. Identifying who the customer is and their requirements is also critical given that the overarching goal for all Six Sigma projects is improving the organization’s ability to meet the needs of its customers.
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Defining and Measuring Quality
Conformance to specifications Performance Quick response Quick-change expertise Features Reliability Durability Serviceability Aesthetics Perceived quality Humanity Value
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Benchmarking
Benchmarking involves comparing an organization's processes with the best practices to be found. Benchmarking is used for a variety of purposes, including: Comparing an organization's processes
with the best organization's processes. Comparing an organization's products and
services with those of other organizations.
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Benchmarking continued
Identifying the best practices to implement.
Projecting trends in order to be able to respond proactively to future challenges and opportunities.
Chapter 4: Six Sigma for Process and Quality Improvement
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Quality Function Deployment (QFD)
Two key drivers of an organization’s long-term competitive success are the extent to which its new products or services meet customers’ needs, and having the organizational capabilities to develop and deliver such new products and services.
Tools for helping translate customer desires directly into product service attributes.
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Four Houses of Quality
Customer requirements Technical requirements Component requirements Process deployment requirements
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House of Quality Details
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The Measure Phase
The measure phase begins with the identification of the key process performance metrics.
Once the key process performance metrics have been specified, related process and customer data is collected.
Two commonly used process performance measures, namely, Defects per Million Opportunities (DPMO) and Process Sigma.
Chapter 4: Six Sigma for Process and Quality Improvement
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Defects Per Million Opportunities
Earlier it was noted that a literal interpretation of Six Sigma is 3.4 defects per million opportunities (DPMO). This may have caused some confusion for more statistically inclined readers, which we shall now attempt to reconcile.
Chapter 4: Six Sigma for Process and Quality Improvement
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Defects Per Million Opportunities
Chapter 4: Six Sigma for Process and Quality Improvement
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Process Sigma
How sigma itself can be used to measure the performance of a process. One way to measure the performance of
a process is to calculate the number of standard deviations the customer requirements are from the process mean or target value.
Chapter 4: Six Sigma for Process and Quality Improvement
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DPMO for Alternative Process Sigma Levels
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Motorola’s Assumption the Process Mean Can Shift by as Much as 1.5 Standard Deviations
Chapter 4: Six Sigma for Process and Quality Improvement
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Comparison of 3 Sigma Process and 6 Sigma Process
Chapter 4: Six Sigma for Process and Quality Improvement
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The Analyze Phase
In this phase our objective is to utilize the data that has been collected to develop and test theories related to the root causes of existing gaps between the process’ current performance and its desired performance.
See next slide Table 4.3 Common tools and methodologies in the Six Sigma toolset.
Chapter 4: Six Sigma for Process and Quality Improvement
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Brainstorming
The brainstorming approach: Do not criticize ideas during the
brainstorming session. Express all ideas no matter how radical,
bizarre, unconventional, ridiculous, or impractical they may seem.
Generate as many ideas as possible. Combine, extend, and/or improve on one
another’s ideas.
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Brainstorming: Actions to Enhance Team Creativity
Create diversified teams. Use analogical reasoning. Use brain writing. Use the Nominal Group Technique. Record team ideas. Use trained facilitators to run the brainstorming
session. Set high standards. Change the composition of the team. Use electronic brainstorming. Make the workplace a playground.
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Cause and Effect Diagrams
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Process Capability Analysis
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Process Capability Analysis continued
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The Improve Phase: Design of Experiments (DOE)
OFAT and 1FAT - one factor at a time. Shortcomings
Not typically possible to test one factor at a time and hold all the other factors constant.
Not possible to account for interactions or joint variation between variables (Figure 4.16).
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Design of Experiments (DOE)
Chapter 4: Six Sigma for Process and Quality Improvement
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DOE: continued
Chapter 4: Six Sigma for Process and Quality Improvement
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DOE: continued
Chapter 4: Six Sigma for Process and Quality Improvement
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DOE continued
Some of the major considerations associated with DOE include: Determining which factors to include in
the experiment. Specifying the levels for each factor. Determining how much data to collect. Determining the type of experimental
design.
Chapter 4: Six Sigma for Process and Quality Improvement
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Taguchi Methods
Design for Manufacturability (DFM) Procedure for statistical testing to
determine best combination of product and transformation system design that will make output relatively independent of normal fluctuations in the production system
Chapter 4: Six Sigma for Process and Quality Improvement
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Statistical Quality Control
Chapter 4: Six Sigma for Process and Quality Improvement
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Chance Versus Assignable Variation
Chance variation is variability built into the system.
Assignable variation occurs because some element of the system or some operating condition is out of control.
Quality control seeks to identify when assignable variation is present so that corrective action can be taken.
Chapter 4: Six Sigma for Process and Quality Improvement
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Control Based on Attributes and Variables
Inspection for Variables: measuring a variable that can be scaled such as weight, length, temperature, and diameter.
Inspection of Attributes: determining the existence of a characteristic such as acceptable-defective, timely-late, and right-wrong.
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Control Charts
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Control Charts
Developed in 1920s to distinguish between chance variation in a system and variation caused by the system’s being out of control - assignable variation.
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Control Charts continued
Repetitive operation will not produce exactly the same outputs.
Pattern of variability often described by normal distribution.
Random samples that fully represent the population being checked are taken.
Sample data plotted on control charts to determine if the process is still under control.
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Control Chart with Limits Set at Three Standard Deviations
Chapter 4: Six Sigma for Process and Quality Improvement
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Control Charts for Variables
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Two Control Charts
Sample Means Chart Range Chart
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Sample Data of Weights of Tacos (Ounces)
Sample Scenario 1 Scenario 2
1 4, 5, 6 4, 5, 6
2 6, 7, 8 3, 5, 7
3 7, 8, 9 2, 5, 8
Chapter 4: Six Sigma for Process and Quality Improvement
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Analysis of Scenario 1
Sample Mean Range
1 5 2
2 7 2
3 8 2Sample means show problem having increased from 5 ounces to 8 ounces. Sample ranges have not changed from sample to sample.
Chapter 4: Six Sigma for Process and Quality Improvement
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Analysis of Scenario 2
Sample Mean Range
1 5 2
2 5 4
3 5 6Sample ranges show problem having increased from 2 ounces to 6 ounces. Sample means have not changed from sample to sample.
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Patterns of Change in Process Distributions
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Control Limits
Sample Means Chart:
RAXLCL
RAXUCL
2X
2X
Range Chart:
RDLCL
RDUCL
3R
4R
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Calculating the Grand Mean and the Average Range
N
RR
N
XX
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Mean Age of Ice Cream
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Range in Ice Cream Age
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Control Charts for Attributes
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Fraction-Defective (p) Charts
pp
pp
p
zp
zp
n
pp
p
LCL
UCL
)1(
sampled units ofnumber total
defects ofnumber total
Chapter 4: Six Sigma for Process and Quality Improvement
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Number-of-Defects (c) Charts
cc
cc
c
zc
zc
c
c
LCL
UCL
sampled units ofnumber
observed incidents ofnumber
Chapter 4: Six Sigma for Process and Quality Improvement
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Six Sigma in Practice
Six Sigma Roles: Master Black Belts. Black Belts. Green Belts. Yellow Belts.
Supporting Roles: Champions/Sponsors. Process owners.
Chapter 4: Six Sigma for Process and Quality Improvement
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Quality in Services
Measuring is difficult Training in standard procedures often
used to improve quality One way to measure quality of services
is to use customer satisfaction surveys J.D. Power and Associates uses
surveys to rate domestic airlines, hotel chains, and rental car companies.
Chapter 4: Six Sigma for Process and Quality Improvement
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Rating the Performance of Domestic Airlines
On-time performance (25%) Airport check-in (11%) Courtesy of flight attendants (11%) Seating comfort (11%)
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Service Defections
Organizations should monitor customer defections feedback from defecting customers can
be used to identify problem areas can determine what is needed to win
them back changes in defection rate can be used as
early warning signal
Chapter 4: Six Sigma for Process and Quality Improvement
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Quality Awards/Certifications
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The Malcolm Baldrige National Quality Award
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ISO 9000
Guidelines for designing, manufacturing, selling, and servicing products.
Selecting an ISO 9000 certified supplier provides some assurance that supplier follows accepted business practices in areas covered by the standard
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Elements of ISO 9000
Management Responsibility Quality System Contract Review Design Control Document and Data Control Purchasing Control of Customer Supplied
Product Product Identification and Traceability Process Control Inspection and Testing
Control of Inspection, Measuring, and Test Equipment
Inspection and Test Status Control of Nonconforming
Product Corrective and Preventive
Action Handling, Storage,
Packaging, Preservation, and Delivery
Internal Quality Audits Training Servicing Statistical Techniques
Chapter 4: Six Sigma for Process and Quality Improvement
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ISO 14000 Series of standards covering environmental
management systems, environmental auditing, evaluation of environmental performance, environmental labeling, and life-cycle assessment.
Intent is to help organizations improve their environmental performance through documentation control, operational control, control of records, training, statistical techniques, and corrective and preventive actions.
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Copyright Copyright John Wiley & Sons, Inc. All rights reserved.
Reproduction or translation of this work beyond that named in Section 117 of the United States Copyright Act without the express written consent of the copyright owner is unlawful. Requests for further information should be addressed to the Permissions Department, John Wiley & Sons, Inc. Adopters of the textbook are granted permission to make back-up copies for their own use only, to make copies for distribution to students of the course the textbook is used in, and to modify this material to best suit their instructional needs. Under no circumstances can copies be made for resale. The Publisher assumes no responsibility for errors, omissions, or damages, caused by the use of these programs or from the use of the information contained herein.
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