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Recent Advances in Statistical Quality Control

Recent Advances in Statistical Quality Control. Prof. Fugee Tsung Hong Kong University of Science and Technology Email: season@ust.hk Quality Lab: http://qlab.ieem.ust.hk. INFORMS International, Hong Kong 2006. Outline. SPC for profiles SPC for engineering controlled processes

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Recent Advances in Statistical Quality Control

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  1. Recent Advances in Statistical Quality Control Prof. Fugee Tsung Hong Kong University of Science and Technology Email: season@ust.hk Quality Lab: http://qlab.ieem.ust.hk

  2. INFORMS International, Hong Kong 2006 Dr. Fugee Tsung, HKUST

  3. Outline • SPC for profiles • SPC for engineering controlled processes • SPC for multistage processes • Quality techniques in service industry Dr. Fugee Tsung, HKUST

  4. Ignore Robust Design Desensitize EPC Compensate SPC Reduce/ Eliminate How to Handle Variation Dr. Fugee Tsung, HKUST

  5. Define Control Measure Improve Analyze Statistical Process Control (SPC): Role in Six Sigma • SPC is emphasized as the major tool used to control and sustain a Six Sigma process Dr. Fugee Tsung, HKUST

  6. I. SPC for Profiles

  7. SPC: Basic Idea ? y In most SPC applications it is assumed that the quality of a process or product can be adequately represented by the distribution of a univariate quality characteristic or by the general multivariate distribution of a vector consisting of several quality characteristics (Woodall et al. 2004). Dr. Fugee Tsung, HKUST

  8. SPC: A Different Idea ? x y In many practical situations, however, the quality of a process or product is better characterized and summarized by a relationship between a response variable and one or more explanatory variables (Woodall et al. 2004). Dr. Fugee Tsung, HKUST

  9. A Profile Example Dr. Fugee Tsung, HKUST

  10. Another Profile Example Dr. Fugee Tsung, HKUST

  11. II. SPC for engineering controlled processes

  12. A Engineering Controlled Process ? x y Process EPC Controller Dr. Fugee Tsung, HKUST

  13. Window of Opportunity Tsung, Shi, and Wu (1999, JQT) Dr. Fugee Tsung, HKUST

  14. Dynamics and autocorrelation • To monitor the engineering controlled process, one may consider monitoring a Dynamic T2 statistic of the form where • Xt = [ yt , xt , yt-1 , xt-1 , …, yt-L , xt-L ]T •  is the covariance matrix of Xt • L is a user-specified time shift factor Tsung and Apley (2002, IIE Trans.) Dr. Fugee Tsung, HKUST

  15. ? Process EPC Controller Incoming signal confounding Model-void assignable causes Output assignable causes Input assignable causes x y Dr. Fugee Tsung, HKUST

  16. Recent results in SPC/EPC • Tsung, F., Wu, H. and Nair, V.N., "On Efficiency and Robustness of Discrete Proportional-Integral Control Schemes," Technometrics, 40, 214-222, 1998. • Tsung, F., Shi, J. and Wu, C.F.J., "Joint Monitoring of PID Controlled Processes," Journal of Quality Technology, 31, 275-285, 1999. • Tsung, F. and Shi, J., "Integrated Design of Run-to-Run PID Controller and SPC Monitoring for Process Disturbance Rejection," IIE Transactions, 31, 517-527, 1999. • Tsung, F., "Improving Automatic-Controlled Process Quality Using Adaptive Principal Component Monitoring," Quality and Reliability Engineering International, 15, 135-144, 1999 • Tsung, F., "On Three-Term Adjustment Schemes for Statistical Process Control," International Journal of Industrial Engineering, 6, 161-170, 1999. • Tsung, F., "Statistical Monitoring and Diagnosis of Automatic Controlled Processes Using Dynamic PCA," International Journal of Production Research, 38, 625-637, 2000. • Tsung, F., "A Note on Statistical Monitoring of Engineering Controlled Processes," International Journal of Reliability, Quality and Safety Engineering, 8, 1-14, 2001. • Tsung, F. and Apley, D.W., " The Dynamic T-squared Chart for Monitoring Feedback-Controlled Processes," IIE Transactions, 34, 1043-1054, 2002. • Shi, D. and Tsung, F., " Modeling and Diagnosis of Feedback-Controlled Processes Using Dynamic PCA and Neural Networks," International Journal of Production Research, 41, 365-380, 2003. • Tsung, F. and Tsui, K.-L., "A Mean Shift Pattern Study on Integration of SPC and APC for Process Monitoring," IIE Transactions, 35, 231-242, 2003. • Tseng, S.-T., Yeh, A. B., Tsung, F., and Chan Y.-Y., " A Study of Variable EWMA Controller," IEEE Transactions on Semiconductor Manufacturing, 16, 633-643, 2003. Dr. Fugee Tsung, HKUST

  17. III. SPC for Multistage processes

  18. Stage 1 Stage k-1 Stage k Stage N A Multistage Process ? yk-1 yk Dr. Fugee Tsung, HKUST

  19. Exposure Black Oxide Lay-up Hot Press Cutting Drilling Inspection ……. Example: Printed Circuit Board Manufacturing From Ding, Shi, and Ceglarek (2002) Dr. Fugee Tsung, HKUST

  20. Multistage Monitoring • The use of single-stage SPC can be misleading and ineffective as its measure is confounded with the cumulative effects from previous stages. • Impact of dynamics and autocorrelation due to the cumulative effects of process dynamics and inertia of serially dependent stages. • How to make use of SPC information accessible outside of the individual process to make better quality control decisions. Dr. Fugee Tsung, HKUST

  21. Multistage Diagnosis • It is critical to trace the source of a defect found in final inspection to a root cause early in the multistage process -- Traceability (Palm et al. 1997) • How to isolate and identify the sources of an out-of-control condition by linking the current stage signal to information about earlier stages in the process • Multistage fault/fraud detection/identification through data mining and knowledge discovery. Dr. Fugee Tsung, HKUST

  22. Recent results in Multistage SPC • Tsung, F., "Impact of Information Sharing on Statistical Quality Control," IEEE Transactions on Systems, Man, and Cybernetics, 30, 211-216, 2000. • Linn, R., Au, E. and Tsung, F., " Process Capability Improvement for Multistage Processes," Quality Engineering, 15, 281-292, 2003. • Shu, L. and Tsung, F., " On Multistage Statistical Process Control," Journal of Chinese Institute of Industrial Engineers, 20, 1-8, 2003. • Shu, L., Tsung, F., and Kapur, K., " Design of Multiple Cause-Selecting Charts for Multistage Processes with Model Uncertainty," Quality Engineering, 16, 437-450, 2004. • Sun, R. and Tsung, F., " Change Pattern Discovery in Multistage Statistical Process Control," International Journal of Industrial Engineering, 11, 261-272, 2004. • Shu, L., Tsung, F., and Tsui, K.-L., " Run-Length Performance of Regression Control Charts with Estimated Parameters," Journal of Quality Technology, 36, 280-292, 2004. • Shu, L., Tsung, F., and Tsui, K.-L., " Effects of Estimation Errors on Cause-Selecting Charts," IIE Transactions, 37, 559-567, 2005. • Xiang, L. and Tsung, F., " Statistical Monitoring of Multistage Processes Based on Engineering Models ," IIE Transactions, in press, 2006. Dr. Fugee Tsung, HKUST

  23. Recent results in autocorrelated/dynamic SPC • Apley, D.W. and Tsung, F., "The Autoregressive T-squared Chart for Monitoring Univariate Autocorrelated Processes," Journal of Quality Technology, 34, 80-96, 2002. • Shu, L., Apley, D.W. and Tsung, F., " Autocorrelated Process Monitoring Using Triggered Cuscore Charts," Quality and Reliability Engineering International, 18, 411-421, 2002. • Jiang, W., Wu, H., Tsung, F., Nair, V.N. and Tsui, K.-L., " PID Charts for Process Monitoring," Technometrics, 44, 205-214, 2002. • Han, D. and Tsung, F., " A Generalized EWMA Control Chart and Its Comparison with the Optimal EWMA, CUSUM and GLR Schemes," The Annals of Statistics, 32, 316-339, 2004. • Han, D. and Tsung, F., " Comparison of the Cuscore, GLRT and CUSUM Control Charts for Detecting a Dynamic Mean Change," The Annals of the Institute of Statistical Mathematics, 57, 531-552, 2005. • Castagliola, P. and Tsung, F., " Autocorrelated Statistical Process Control for Non-Normal Situations," Quality and Reliability Engineering International, 21, 131-161, 2005. • Han, D. and Tsung, F., “A Reference-Free Cuscore Chart for Dynamic Mean Change Detection and a Unified Framework for Charting Performance Comparison,” Journal of the American Statistical Association, in press, 2006. Dr. Fugee Tsung, HKUST

  24. Recent results in process diagnosis and improvement • Sun, R. and Tsung, F., " A Kernel-Distance-Based Multivariate Control Chart using Support Vector Methods," International Journal of Production Research, 41, 2975-2989, 2003. • Tong, J., Tsung, F., and Yen, B., " A DMAIC Approach for Printed Circuit Board Quality Improvement," International Journal of Advanced Manufacturing Technology, 23, 523-531, 2004. • Shi, D., Tsung, F., and Unsworth, P., " Adaptive Time-Frequency Decomposition for Transient Vibration Monitoring of Rotating Machinery," Mechanical Systems and Signal Processing, 18, 127-141, 2004. • Sun, R., Tsung, F., and Qu, L., " Combining bootstrap and genetic programming for feature discovery in diesel engine diagnosis," International Journal of Industrial Engineering, 11, 273-281, 2004. • Lee, N., An, Y, and Tsung, F., " Studying Effects of Screw-Fastening Process On Assembly Accuracy ," International Journal of Advanced Manufacturing Technology, 25, 493-499, 2005. Dr. Fugee Tsung, HKUST

  25. VI. Quality Techniques in Service Industry

  26. Six Sigma in Financial Service

  27. 港基應用「六個標準差」 即時見效 港基公布中期業績，港基因為應用到國際大企業最流行的管理方法︰「Six Sigma」（六個標準差，統計學用語，目的是減少生產過程中的錯誤），而在營運開支方面減少 1.4%。 究竟甚麼是六個標準差？對銀行如此有利？ 六個標準差源自 1986 年美國 Motorola 公司通訊部門提出的一項嶄新作法，使公司在 1987 至 1997 年的十年推行期：每年銷售增長五倍；節省的成本更達 140 億美元。 近年因美國通用電氣（GE）大力推行六個標準差，結果使其獲利屢創新高，更讓顧客滿意度大幅提升。也因此引起品質管理界所重視，並開始蔚為風潮。 看似神效無比，相信對近年積極開源節流的本地銀行家來說，也會對這個妙用無窮的六個標準差極有興趣… -- 香港經濟日報 2002-08-05 Dr. Fugee Tsung, HKUST

  28. Six Sigma in Insurance

  29. A Thank You Letter… Date:Wed, September 14, 2005 11:30 am Dear Fugee, I am pleased to let you know that I have joined AIA since March this year.  I am working on a Six Sigma deployment program (They call it Performance Management Program here) in AIA's six Southeast Asian operations.  Insurance operations are new to me but the underlying processes and principles are very close to banks.  My major responsibility is to drive and deliver performance metrics as well as project facilitation. I would like to thank you again for your guidance and sharing of Six Sigma knowledge.   Best regards, XXXX XX --------------------------------------------------------- AIA Performance Management Program Tel.  (852) XXXX XXXX Fax. (852) XXXX XXXX Dr. Fugee Tsung, HKUST

  30. Six Sigma in Telecommunication Service

  31. XXXXXX Project Name: Black Belt/Green Belt Leader Business Function: Project Initiation Date: DEFINE/ MEASURE ANALYZE IMPROVE CONTROL Dr Fugee Tsung SIX SIGMA PROJECT COVER SHEET NWTbb Hotline Service Support 13 Aug 05 DEFINE/MEASURE ANALYZE Initial Process Performance (Zigma): 2.64 Process Graph: Target Process (Zigma: 3 Prioritization Tool for x’s: Fishbone to determine key process input Matrix Flow & SIPOC to review the whole service process XXXXXX T-Test and DOE IMPROVE & CONTROL SUSTAIN Ending Process ‘Z’ Value: Zst 4.38 & Zlt 3.45 Business Benefit(s): $55K/mth ($333K for 6 mths) Documentation Transferred to Process Owner? Y N XXXXX Completion Dates Planned: 9 Sep 05 Oct end mid Nov mid Dec 9 Dec Actual: 31 Dec 9 Sep 05 31 Oct 05

  32. Six Sigma in the Hospitality Industry

  33. Since 2003 Six Sigma is also launched at the Sheraton Hotel in Hong Kong • Most common used Six Sigma tools at the Sheraton Hotel: • DMAIC • Process map • Fishbone diagram • Pareto charts • Hypothesistests • Training were given to staff • Evaluation of how successful six sigma program is through measurement of “return vs expense ratio” Dr. Fugee Tsung, HKUST

  34. Six Sigma in Healthcare

  35. Few references • “The Use of Control Charts in Health-Care and Public-Health Surveillance” by Woodall, April 2006, JQT – a discussion paper. • Tsung, F., Zhou, Z.H., and Jiang, W., " Applying Manufacturing Batch Techniques to Fraud Detection with Incomplete Customer Information ," IIE Transactions, in press, 2006. Dr. Fugee Tsung, HKUST

  36. Define Control Measure Improve Analyze Conclusion • SPC research for business excellence • HKUST Quality Lab: http://qlab.ieem.ust.hk • Six Sigma Quality Research Center (SSQRC) in Nansha (coming soon!) • Prof. Tsung’s email: season@ust.hk Dr. Fugee Tsung, HKUST

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