Quality Control and Improvement Chapter 9 INTRODUCTION to Operation Management  4e, Schroeder Copyright © 2008 by The McGr...
Chapter Outline <ul><li>Design of Quality Control Systems </li></ul><ul><li>Process Quality Control </li></ul><ul><li>Attr...
Chapter Emphasis <ul><li>Process definition </li></ul><ul><li>Statistical quality control </li></ul><ul><li>Continuous imp...
Design of Quality Control Systems <ul><li>Break down production process into subprocesses and “internal customers.” </li><...
Steps in Designing QC Systems <ul><li>Identify critical points </li></ul><ul><ul><li>Incoming materials & services </li></...
Types Of Measurement <ul><li>Attribute measurement </li></ul><ul><ul><li>Product characteristic evaluated with a discrete ...
When the Inspector Finds a Defect… <ul><li>Containment:  Keep the defective items from getting to the customer </li></ul><...
When the Inspector Finds a Defect  e.g.  Strap on backpack comes loose <ul><li>Containment:  pull the bad backpacks from t...
Process Quality Control <ul><li>Basic assumptions (tenets) of Process Quality Control: </li></ul><ul><ul><li>Every process...
“ It’s our job to drive the randomness out.” --Bill James, statistician for the Boston Red Sox Wall Street  Journal, 20 Ju...
Process Quality Control <ul><li>Assignable (special) causes </li></ul><ul><ul><li>Can be identified and corrected </li></u...
Attributes & Variables <ul><li>Attributes are counts, such as the number (or proportion) of defects in a sample. </li></ul...
Statistical Formulas <ul><li>Mean (average), Standard deviation, Range </li></ul><ul><li>Binomial distribution ( success (...
Process Control Chart (Figure 9.1) x y Time 9-
Quality Control Chart (Figure 9.2) Stop the process; look for assignable cause Stop the process; look for assignable cause...
Formulas for SPC (3 Sigma) <ul><li>p -Chart </li></ul><ul><li>x-Bar Chart </li></ul><ul><li>R-Chart </li></ul>9-
Issues in Using Control Charts <ul><li>Sample Size </li></ul><ul><ul><li>large enough to detect defectives </li></ul></ul>...
Continuous Improvement <ul><li>Aim of continuous improvement is to reduce the variability of the product or process </li><...
Pareto Analysis Note:  40 percent of the items cause 78.6 percent of the defects 9-
Pareto Diagram (Figure 9.3) 9-
Cause-and-effect  (Fish-bone, Ishikawa)  diagram  (Figure 9.4) 9-
Process Capability Index Examples (Figure 9.5) frequency process measure process measure 9-
Computation of  C pk  (Figure 9.6) frequency process measure process measure 9-
Six-Sigma Quality <ul><li>Pioneered by Motorola in 1988 (Juran claims credit for the idea). </li></ul><ul><li>3.4 defects ...
Six Sigma Quality <ul><li>Process Improvement steps of Six Sigma (DMAIC): </li></ul><ul><ul><li>Define (process to improve...
Six Sigma Quality <ul><li>Six Sigma uses a project/team approach. </li></ul><ul><li>A process is selected for improvement ...
Lean and Six Sigma <ul><li>Are complementary approaches to improvement. </li></ul><ul><ul><li>Lean seeks to eliminate wast...
Quality Control and Improvement  in Industry <ul><li>75% use process control charts. </li></ul><ul><li>More use of variabl...
Quality Control and Improvement  in Industry <ul><li>The seven tools of quality control </li></ul><ul><ul><li>Flowcharts <...
Service Quality <ul><li>Service measures are perceptual or subjective </li></ul><ul><li>SERVQUAL  most popular measure </l...
Summary <ul><li>Design of Quality Control Systems </li></ul><ul><li>Process Quality Control </li></ul><ul><li>Attribute Co...
End of Chapter Nine 9-
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Quality Control and Improvement Chapter 9

  1. 1. Quality Control and Improvement Chapter 9 INTRODUCTION to Operation Management 4e, Schroeder Copyright © 2008 by The McGraw-Hill Companies, Inc., All Rights Reserved. McGraw-Hill/Irwin
  2. 2. Chapter Outline <ul><li>Design of Quality Control Systems </li></ul><ul><li>Process Quality Control </li></ul><ul><li>Attribute Control </li></ul><ul><li>Variables Control </li></ul><ul><li>Using Control Charts </li></ul><ul><li>Continuous Improvement </li></ul><ul><li>Six Sigma </li></ul><ul><li>Lean and Six Sigma </li></ul><ul><li>Quality Control and Improvement in Industry </li></ul>9-
  3. 3. Chapter Emphasis <ul><li>Process definition </li></ul><ul><li>Statistical quality control </li></ul><ul><li>Continuous improvement </li></ul>9-
  4. 4. Design of Quality Control Systems <ul><li>Break down production process into subprocesses and “internal customers.” </li></ul><ul><li>Identify “Critical points” where inspection or measurement should take place </li></ul><ul><li>Four steps in designing QC systems. </li></ul>9-
  5. 5. Steps in Designing QC Systems <ul><li>Identify critical points </li></ul><ul><ul><li>Incoming materials & services </li></ul></ul><ul><ul><li>Work in process </li></ul></ul><ul><ul><li>Finished product or service </li></ul></ul><ul><li>Decide on the type of measurement </li></ul><ul><ul><li>Variables (continuous scale, diameter, weight, tensile strength) </li></ul></ul><ul><ul><li>Attribute (number of defect per unit) </li></ul></ul><ul><li>Decide on the amount of inspection to be used. </li></ul><ul><ul><li>Sample size </li></ul></ul><ul><li>Decide who should do the inspection </li></ul><ul><ul><li>Worker inspection or outside inspection </li></ul></ul>9-
  6. 6. Types Of Measurement <ul><li>Attribute measurement </li></ul><ul><ul><li>Product characteristic evaluated with a discrete choice: </li></ul></ul><ul><ul><ul><li>Good/bad, yes/no </li></ul></ul></ul><ul><li>Variables measurement </li></ul><ul><ul><li>Product characteristic that can be measured on a continuous scale: </li></ul></ul><ul><ul><ul><li>Length, size, weight, height, time, velocity </li></ul></ul></ul>9-
  7. 7. When the Inspector Finds a Defect… <ul><li>Containment: Keep the defective items from getting to the customer </li></ul><ul><li>Correction: Find the cause of the defect and correct it. </li></ul><ul><li>Prevention: Prevent the cause from happening again. </li></ul><ul><li>Continuously improve the system. </li></ul>9-
  8. 8. When the Inspector Finds a Defect e.g. Strap on backpack comes loose <ul><li>Containment: pull the bad backpacks from the line. </li></ul><ul><li>Correction: sewing machine misaligned; fix it. </li></ul><ul><li>Prevention: why was it misaligned? Find out and change system to prevent it happening again. </li></ul><ul><li>Continuously monitor and improve system. </li></ul>9-
  9. 9. Process Quality Control <ul><li>Basic assumptions (tenets) of Process Quality Control: </li></ul><ul><ul><li>Every process has random variation in it. </li></ul></ul><ul><ul><li>Production processes are not usually found in a state of control. </li></ul></ul><ul><li>“ State of Control”; what does it mean? </li></ul><ul><ul><li>Unnecessary variation is eliminated. </li></ul></ul><ul><ul><li>Remaining variation is because of random causes. </li></ul></ul>9-
  10. 10. “ It’s our job to drive the randomness out.” --Bill James, statistician for the Boston Red Sox Wall Street Journal, 20 June 2007, p. D7. 9-
  11. 11. Process Quality Control <ul><li>Assignable (special) causes </li></ul><ul><ul><li>Can be identified and corrected </li></ul></ul><ul><li>Common causes </li></ul><ul><ul><li>Occur randomly </li></ul></ul><ul><ul><li>Cannot be changed unless process is redesigned </li></ul></ul>9-
  12. 12. Attributes & Variables <ul><li>Attributes are counts, such as the number (or proportion) of defects in a sample. </li></ul><ul><li>Variables are measures (mean & range or standard deviation) of critical characteristics in a sample. </li></ul>9-
  13. 13. Statistical Formulas <ul><li>Mean (average), Standard deviation, Range </li></ul><ul><li>Binomial distribution ( success (1), failure(0) ) </li></ul><ul><li>LCL(lower control limit), UCL(upper control limit) </li></ul>9-
  14. 14. Process Control Chart (Figure 9.1) x y Time 9-
  15. 15. Quality Control Chart (Figure 9.2) Stop the process; look for assignable cause Stop the process; look for assignable cause Stop the process; look for assignable cause Stop the process; look for assignable cause 9-
  16. 16. Formulas for SPC (3 Sigma) <ul><li>p -Chart </li></ul><ul><li>x-Bar Chart </li></ul><ul><li>R-Chart </li></ul>9-
  17. 17. Issues in Using Control Charts <ul><li>Sample Size </li></ul><ul><ul><li>large enough to detect defectives </li></ul></ul><ul><ul><li>variables can use smaller sample sizes </li></ul></ul><ul><li>How often to sample? </li></ul><ul><ul><li>Depends upon cost </li></ul></ul><ul><li>Control limits vs. product specifications </li></ul><ul><ul><li>Is the process capable of producing to specs? </li></ul></ul><ul><ul><li>Are the specifications appropriate? </li></ul></ul>9-
  18. 18. Continuous Improvement <ul><li>Aim of continuous improvement is to reduce the variability of the product or process </li></ul><ul><li>Techniques for continuous improvement </li></ul><ul><ul><li>Pareto analysis </li></ul></ul><ul><ul><li>Cause-and-effect (fish-bone) diagrams </li></ul></ul><ul><ul><li>Process capability indicies </li></ul></ul>9-
  19. 19. Pareto Analysis Note: 40 percent of the items cause 78.6 percent of the defects 9-
  20. 20. Pareto Diagram (Figure 9.3) 9-
  21. 21. Cause-and-effect (Fish-bone, Ishikawa) diagram (Figure 9.4) 9-
  22. 22. Process Capability Index Examples (Figure 9.5) frequency process measure process measure 9-
  23. 23. Computation of C pk (Figure 9.6) frequency process measure process measure 9-
  24. 24. Six-Sigma Quality <ul><li>Pioneered by Motorola in 1988 (Juran claims credit for the idea). </li></ul><ul><li>3.4 defects per million </li></ul><ul><li>Six sigma criterion is equivalent to C pk = 1.5 </li></ul><ul><li>Sample size rules become unusable </li></ul><ul><li>Most process are 4 sigma, e.g. payroll, prescriptions, baggage handling, journal vouchers, restaurant bills. (.62%) </li></ul><ul><li>Airline fatalities are 6.4 sigma </li></ul><ul><li>IRS tax advice is less than 2 sigma ( > 31%) </li></ul><ul><li>Criticism: accepts 3.4 defects/million. Is not zero defects. </li></ul>9-
  25. 25. Six Sigma Quality <ul><li>Process Improvement steps of Six Sigma (DMAIC): </li></ul><ul><ul><li>Define (process to improve, project specification) </li></ul></ul><ul><ul><li>Measure (quality variables, goals) </li></ul></ul><ul><ul><li>Analyze (find root causes and alternatives) </li></ul></ul><ul><ul><li>Improve (process change, check for improvement) </li></ul></ul><ul><ul><li>Control (ensure improvement is not lost over time) </li></ul></ul>9-
  26. 26. Six Sigma Quality <ul><li>Six Sigma uses a project/team approach. </li></ul><ul><li>A process is selected for improvement </li></ul><ul><li>A cross-functional team is formed. </li></ul><ul><li>A six sigma ‘black belt’ is chosen to head the team. </li></ul><ul><li> champion, master black belt, black belt </li></ul><ul><li>The team uses the DMAIC method for finding root causes and improving the process. </li></ul>9-
  27. 27. Lean and Six Sigma <ul><li>Are complementary approaches to improvement. </li></ul><ul><ul><li>Lean seeks to eliminate waste. </li></ul></ul><ul><ul><li>Six sigma seeks to eliminate defects. </li></ul></ul><ul><li>Six sigma organization is more formal and training intensive. </li></ul><ul><li>Six sigma is project focused; lean is more broad based. </li></ul>9-
  28. 28. Quality Control and Improvement in Industry <ul><li>75% use process control charts. </li></ul><ul><li>More use of variable (x-bar and R) charts than attribute (p) charts because of sample size requirements. </li></ul><ul><li>“ The Seven Tools of Quality Control” (see Figure 9.7) </li></ul><ul><li>Quality control in the service industry (SERVQUAL) </li></ul>9-
  29. 29. Quality Control and Improvement in Industry <ul><li>The seven tools of quality control </li></ul><ul><ul><li>Flowcharts </li></ul></ul><ul><ul><li>Pareto charts </li></ul></ul><ul><ul><li>Cause-and-effect diagrams </li></ul></ul><ul><ul><li>Run (trend) charts </li></ul></ul><ul><ul><li>Histograms </li></ul></ul><ul><ul><li>Control charts </li></ul></ul><ul><ul><li>Scatter diagrams </li></ul></ul>9-
  30. 30. Service Quality <ul><li>Service measures are perceptual or subjective </li></ul><ul><li>SERVQUAL most popular measure </li></ul><ul><ul><li>Tangibles ( 유형 , 치과 : 인테리어 , 기계 ) </li></ul></ul><ul><ul><li>Reliability ( 신뢰성 , 예약 , 자리지킴 ) </li></ul></ul><ul><ul><li>Responsiveness ( 반응 , 방문시 인사 , 처치 후 ) </li></ul></ul><ul><ul><li>Assurance ( 보장 , 실력 , 치료성과 ) </li></ul></ul><ul><ul><li>Empathy ( 공감 , 꼼꼼함 , 덜 아픔 , 자세한 설명 ) </li></ul></ul>
  31. 31. Summary <ul><li>Design of Quality Control Systems </li></ul><ul><li>Process Quality Control </li></ul><ul><li>Attribute Control </li></ul><ul><li>Variables Control </li></ul><ul><li>Using Control Charts </li></ul><ul><li>Continuous Improvement </li></ul><ul><li>Six Sigma </li></ul><ul><li>Lean and Six Sigma </li></ul><ul><li>Quality Control and Improvement in Industry </li></ul>9-
  32. 32. End of Chapter Nine 9-
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