Quality book lecture
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Transcript of Quality book lecture
Chapter 1 1Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery. Copyright (c) 2012 John Wiley & Sons, Inc.
IE 4653/6653 Industrial Quality Control I
Lecture 1
Quality Improvement in the Modern Business Environment
Chapter 1
Chapter 1 2Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery. Copyright (c) 2012 John Wiley & Sons, Inc.
Definitions - Meaning of Quality and Quality Improvement
The Eight Dimensions of Quality1. Performance - Will the product do the intended job?
2. Reliability - How often does the product fail?
3. Durability - How long does the product last?
4. Serviceability - How easy is it to repair the product?
5. Aesthetics - What does the product look like?
6. Features - What does the product do?
7. Perceived Quality - What is the reputation of the company or its product?
8. Conformance to Standards - Is the product made exactly as the designer intended?
Chapter 1 3Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery. Copyright (c) 2012 John Wiley & Sons, Inc.
Definitions• Quality means fitness for use
– This is a traditional definition
– Quality of design
– Quality of conformance
• Quality is inversely proportional to variability– This is a modern definition of quality
Chapter 1 4Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery. Copyright (c) 2012 John Wiley & Sons, Inc.
Water Faucet Example• Target: best performance when internal diameter =
1.25cm• 100 faucets from supplier A, 100 from supplier B,
100 from supplier C• Supplier A: mean diameter 1.25cm, every faucet close
to target• Supplier B: mean diameter 2cm• Supplier C: mean diameter 1.25cm, faucets more
variable• Conclusion: A has the best quality
Chapter 1 5Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery. Copyright (c) 2012 John Wiley & Sons, Inc.
Quality Improvement• Quality improvement is the reduction of variability in
processes and products
• The water faucet example illustrates the utility of this definition
• An equivalent definition is that quality improvement is the elimination of waste. This is useful in service or transactional businesses.
Chapter 1 6Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery. Copyright (c) 2012 John Wiley & Sons, Inc.
Terminology• Quality (critical-to-quality) characteristics
– Physical: length. weight, voltage, viscosity– Sensory: taste, appearance, color– Time orientation: reliability, durability, serviceability
• Statistical methods: describe the variability– Variables data: continuous measurements
• Length• Voltage• Viscosity
– Attributes data: discrete data• # of emergency room arrivals
Chapter 1 7Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery. Copyright (c) 2012 John Wiley & Sons, Inc.
Terminology cont’d• Specifications
– Lower specification limit– Upper specification limit– Target or nominal values
• Defective or nonconforming product• Defect or nonconformity
– A specific type of failure
• Not all products containing a defect are necessarily defective
Chapter 1 8Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery. Copyright (c) 2012 John Wiley & Sons, Inc.
Statistical Methods for Quality Control and Improvement
Chapter 1 9Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery. Copyright (c) 2012 John Wiley & Sons, Inc.
Statistical Methods• Statistical process control (SPC)
– Control charts, plus other problem-solving tools– Useful in monitoring processes, reducing variability
through elimination of assignable causes– On-line technique
• Design of experiments (DOE)– Discovering the key factors that influence process
performance– Process optimization– Off-line technique
• Acceptance Sampling
Chapter 1 10Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery. Copyright (c) 2012 John Wiley & Sons, Inc.
Typing Example• Consider improvement of typing quality, which is measured by
typing accuracy and clearness. • Statistical process control (SPC) - Every hour one page is selected
and its quality is measured. Plot the measurements from each hour on a control chart. If a shift of quality is detected, the root cause of this shift (e.g., typist tiredness, lack of ink) is identified and fixed.
• Design of experiment (DOE) - Conduct experiments with combinations of different typists, typewriters, papers, working schedules. The best combination of these factors are selected to achieve optimal typing quality.
• Acceptance sampling - Several sample pages are inspected from every “lot” (e.g., every 100 typed pages). If the selected sample pages have satisfactory quality, the whole “lot” is accepted. Otherwise, the whole lot is rejected and rework should be done.
Chapter 1 11Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery. Copyright (c) 2012 John Wiley & Sons, Inc.
Walter A. Shewart (1891-1967)• Trained in engineering and physics
• Long career at Bell Labs
• Developed the first control chart about 1924
Statistical Process Control
Chapter 1 12Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery. Copyright (c) 2012 John Wiley & Sons, Inc.
Design of Experiments
Chapter 1 13Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery. Copyright (c) 2012 John Wiley & Sons, Inc.
Acceptance Sampling
• Outgoing inspection− Inspection before the
product is shipped to the customer
• Incoming inspection− Inspection after the
product is received from the supplier
• Disposition of lots
Chapter 1 14Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery. Copyright (c) 2012 John Wiley & Sons, Inc.
Variation Reduction Approaches
Chapter 1 15Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery. Copyright (c) 2012 John Wiley & Sons, Inc.
Effective management of quality requires the execution of three activities• Quality Planning
– Strategic activity
• Quality Assurance– Ensure the quality levels of products and services are properly
maintained
• Quality Control and Improvement– Ensure the products and services meet requirements and are
improved on a continuous basis
Management Aspects of Quality Improvement
Chapter 1 16Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery. Copyright (c) 2012 John Wiley & Sons, Inc.
Shewhart Cycle
Chapter 1 17Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery. Copyright (c) 2012 John Wiley & Sons, Inc.
Statistical Quality Control Procedures
Process
DecisionFormulate action Data analysis
EvaluationFaulty discovery
Diagnosis
Take actionImplementation
Data collectionObservation
Chapter 1 18Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery. Copyright (c) 2012 John Wiley & Sons, Inc.
Six Sigma• A disciplined and analytical approach to process and
product improvement• First developed by Motorola in the late 1980s• Specialized roles for people; Master Black belts, Black
Belts, Green Belts• BBs and MBBs have responsibility (project definition,
leadership, training/mentoring, team facilitation)• Involves a five-step process (DMAIC)
– Define – Measure– Analyze– Improve– Control
Chapter 1 19Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery. Copyright (c) 2012 John Wiley & Sons, Inc.
• Three sigma quality− 2700 ppm defective− (0.9973)100=0.7631
• Six sigma quality− 0.002 ppm defective− (0.999999998)100=0.9999998
• Three sigma quality− 66810 ppm defective
• Six sigma quality− 3.4 ppm defective
Chapter 1 20Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery. Copyright (c) 2012 John Wiley & Sons, Inc.
Why “Quality Improvement” is Important: A Simple Example
• A visit to a fast-food store: Hamburger (bun, meat, special sauce, cheese, pickle, onion, lettuce, tomato), fries, and drink.
• This product has 10 components - is 99% good okay?
10
4
12
{Single meal good} (0.99) 0.9044
Family of four, once a month: {All meals good} (0.9044) 0.6690
{All visits during the year good} (0.6690) 0.0080
P
P
P
10 4
12
{single meal good} (0.999) 0.9900, {Monthly visit good} (0.99) 0.9607
{All visits in the year good} (0.9607) 0.6186
P P
P
Chapter 1 21Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery. Copyright (c) 2012 John Wiley & Sons, Inc.
Three Generations of Six Sigma Implementations
• Generation I– Defect elimination and basic variability reduction
• Generation II– Emphasis on variability and defect reduction remained– Strong effort to business performance improvement
through cost reduction
• Generation III– Additional focus of creating value throughout the
organization and for its stakeholders
Chapter 1 22Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery. Copyright (c) 2012 John Wiley & Sons, Inc.
Lean Systems• Focuses on elimination of waste
– Long cycle times– Long queues – in-process inventory– Inadequate throughput– Rework– Non-value-added work activities
• Makes use of many of the tools of operations research and industrial engineering– Discrete-event simulation
Chapter 1 23Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery. Copyright (c) 2012 John Wiley & Sons, Inc.
Lean Focuses on Waste Elimination• Definition
– A set of methods and tools used to eliminate waste in a process
– Lean helps identify anything not absolutely required to deliver a quality product on time.
• Benefits of using Lean– Lean methods help reduce inventory, lead time,
and cost– Lean methods increase productivity, quality, on
time delivery, capacity, and sales