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04/21/23 ENGM 720: Statistical Process Control
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ENGM 720 - Lecture 02
Introduction to Statistical Process Control
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Assignment:
Reading:• Chapter 1
• Cursory reading
• Chapter 2 & 3
• Start reading
Assignment 1:
• Review / obtain access to MS Excel• Verify access to the Data Analysis Add-In
• Make sure you can access the class website• Make a trial download of the Red Bead data spreadsheet
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Meaning of Quality and Quality Improvement Quality – one of most important consumer
decision factors in selecting products and services
Understanding / improving quality is key factor for success, growth, and competitive position
Substantial return on investment comes from:• Improved quality• Successful implementation of quality techniques as
overall business strategy
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Dimensions of Quality Performance – Will the product do the intended job? Reliability – How often does the product fail? Durability - How long does the product last? Serviceability – How easy is it to repair the product? Aesthetics – What does the product look like? Features – What does the product do? Perceived quality – What is the reputation of the company
or product? Conformance to standards – Is the product made exactly
as the designer intended?
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Quality is a multifaceted entity.
Traditional (OLD) definition of Quality:• Fitness of use
(i.e., products must meet requirements of those who use them.)
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Two Aspects of “Fitness for use”
Quality of design – • all products intentionally made in various grades of
quality. (e.g., Autos differ with respect to size, options, speed, etc.)
Quality of conformance – • how well the product conforms to specifications. (e.g.,
If diameter of a drilled hole is within specifications then it has good quality.)
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What's Wrong with "Fitness for Use" Definition of Quality?
Unfortunately, quality as “Fitness for Use” has become associated with the "conformance to specifications" regardless of whether or not the product is fit for use by customer.
Misconception: • Quality can be dealt with solely in manufacturing -
that is, by "gold plating" the product
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Modern Definition of Quality:Quality is inversely proportional to variability If variability of product decreases quality of
product increases
Quality Improvement – • Reduction of variability in processes and products
Quality Engineering – • Set of operational, managerial, and engineering
activities that a company uses to ensure that quality characteristics of a product are at nominal levels
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Statistical Methods for Quality Improvement
Relative Savings from a $1 investment in:
• Acceptance Sampling ($1)
• On-Line Process Control ($10)
• Off-Line Process Improvement ($100)
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Acceptance Sampling
Reduces bad product sent to consumer• Dodge & Romig 1930s
Sample from lot to determine acceptance
More effective than 100% inspection No feedback, prevention or improvement
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On-Line Process Control
Monitoring of manufacturing process with control charts • Shewhart 1920s
Sample & stop process if necessary
No improvement, but maintains current process quality level
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Off-Line Improvement
Designed experiments • Taguchi & Classical Statistics 1980s
If it's not broke, improve it!
Continuous improvement of product designs and manufacturing processes
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$
Defect Rate
Quality Cost
Quality Myth:Higher Quality Higher Cost
Failure Cost
Total Cost
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Manufacturing Process$20 / part
75% Conform
Very Often:Higher Quality Lower Cost
Textbook ex: Manufacture of Copier Part
$20 100 $4 15cos$22.89
90
t
good part
Re-work Process$4 / part
(15 good parts)
25% Non-conforming:
100 parts
(75 good parts)
(25 parts)(40% Scrap, 60% Re-workable)
(10 scrap parts)
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New SQC procedure implemented• NOW: manufacturing non-conformity = 5%
• SAVINGS: $22.89 – $20.53 = $2.36 / good part
• PRODUCTIVITY: 9% improvement
Study finds excessive process variability responsible for high nonconformity rate
$20 100 $4 3cos$20.53
98
t
good part
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How Quality Engineering Makes a Company More Competitive
Tactical• less inspection
• less scrap and rework
• more capacity
• easier scheduling & shorter lead time
• less inventory
• less warranty cost
Strategic• more flexibility to make
new products
• customer satisfaction
• easier to spot and solve problems
• employee involvement in continuous improvement
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Taguchi (1980) and Robust Design
New Goal: consistently good performance in a variety of operating conditions
Minimize variation in processes and products
Use Designed Experiments to achieve
robustness
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Taguchi's Example:Elasticity of Caramel
• Product X conforms to elasticity spec at 72o
• Product Y performs well in a wide variety of operating conditions
Elasticity
Temp72o
SpecProd Y
Prod X
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Total Quality Management – TQM
Although statistical techniques are critical for quality improvement:
• the management system must direct quality improvement philosophy and ensure its implementation in all aspects of business
• TQM must be implemented within a management system that is scientifically quality driven
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International Standards Organization ISO 9000 (1990s) An ISO 9000 certified company
• examined by a registered official• has an effective management system, capable of
consistent performance
Examples: • System in place to correctly identify customer needs• Staff have correct versions of documentation• Preferred suppliers selected; consistent
communication system • System to document and correct errors
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Six Sigma - Motorola
Six Sigma = 3.4 defects per million opportunities!
Every employee must show bottom line results of quality project – finance, mail room, manufacturing, etc.• identify problem;
• develop measurement;
• set goal;
• close gap
Long term process – 5 years to fully implement
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Malcolm Baldridge National Quality Award
Established by congress in 1987, for excellence in organizations
Applicant receives intense investigation NIST (National Institute of Standards and
Technology) study shows Baldrige Award recipients outperformed the Standard & Poor’s 500 by nearly 2.5 to 1.
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The Baldridge Award examines quality of organization in seven categories
1. Leadership 2. Information and Analysis 3. Strategic Planning 4. Human Resource Development and
Management 5. Process Management 6. Business Results 7. Customer Focus and Satisfaction
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Questions & Issues
On-Campus Students• Please turn in card info
Distance students:• E-mail instructor with card info, including
proctor contact information• Name
• E-mail Address
• Mailing Address