Recent Advances in Statistical Quality Control
Prof. Fugee TsungHong Kong University
of Science and TechnologyEmail: [email protected]
Quality Lab: http://qlab.ieem.ust.hk
Dr. Fugee Tsung, HKUST 2
INFORMS International, Hong Kong 2006
Dr. Fugee Tsung, HKUST 3
Outline
I. SPC for profilesII. SPC for engineering
controlled processesIII. SPC for multistage processesIV. Quality techniques in service
industry
Dr. Fugee Tsung, HKUST 4
Ignore
DesensitizeRobust Design
CompensateEPC
Reduce/Eliminate
SPC
How to Handle Variation
Dr. Fugee Tsung, HKUST 5
Statistical Process Control (SPC): Role in Six Sigma
SPC is emphasized as the major tool used to control and sustain a Six Sigma process
Define
Improve Analyze
MeasureControl
I. SPC for Profiles
Dr. Fugee Tsung, HKUST 7
SPC: Basic Idea
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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).
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Dr. Fugee Tsung, HKUST 8
SPC: A Different Idea
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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).
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Dr. Fugee Tsung, HKUST 9
A Profile Example
Dr. Fugee Tsung, HKUST 10
Another Profile Example
II. SPC for engineering controlled processes
Dr. Fugee Tsung, HKUST 12
A Engineering Controlled Process
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Process
EPC Controller
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Dr. Fugee Tsung, HKUST 13
Window of Opportunity
(a) (b)
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
tTt
Lt XXDT 1
Tsung and Apley (2002, IIE Trans.)
Dr. Fugee Tsung, HKUST 15
Incoming signal confounding
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EPC Controller
Input assignable causes Output assignable causes
Model-void assignable causes
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.
III. SPC for Multistage processes
Dr. Fugee Tsung, HKUST 18
A Multistage Process
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Dr. Fugee Tsung, HKUST 19
Example: Printed Circuit Board Manufacturing
Exposure
Black Oxide
Lay-up
Hot Press
Cutting
Drilling
Inspection
…….
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.
VI. Quality Techniques in Service Industry
Six Sigma in Financial Service
Dr. Fugee Tsung, HKUST 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
Six Sigma in Insurance
Dr. Fugee Tsung, HKUST 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 XXXXFax. (852) XXXX XXXX
Six Sigma in Telecommunication Service
Dr. Fugee Tsung, HKUST
SIX SIGMA PROJECT COVER SHEET
CompletionDates Planned:
Actual:
DEFINE/ MEASURE ANALYZE IMPROVE CONTROL
Project Name:Black Belt/Green Belt LeaderBusiness Function:Project Initiation Date:
DEFINE/MEASURE ANALYZE
IMPROVE & CONTROL SUSTAIN
Initial Process Performance (Zigma): 2.64
Process Graph:
Target Process (Zigma: 3
Prioritization Tool for x’s:
Ending Process ‘Z’ Value:
Business Benefit(s):
Documentation Transferred to Process Owner? Y N
XXXXXX Dr Fugee Tsung
NWTbb Hotline Service Support
13 Aug 05
Fishbone to determine key process input
Matrix Flow & SIPOC to review the whole service process
T-Test and DOE
Vital X What ToolPrevioussetting New Setting
ControlProcedure
1Workflow review
(11 actions) Details of actions & control mechanism in page 2-3)
2Saff skill set(3 actions) Details of actions & control mechanism in page 3)
3 Testing tools Details of actions & control mechanism in page 3)
Zst 4.38 & Zlt 3.45
$55K/mth ($333K for 6 mths)
XXXXX
9 Sep 05
9 Sep 05 31 Oct 05
Oct end
9 Dec
mid Nov mid Dec
31 Dec
XXXXXX
Six Sigma in the Hospitality Industry
Dr. Fugee Tsung, HKUST 33
Most common used Six Sigma tools at the Sheraton Hotel:
DMAIC Process map Fishbone diagram Pareto charts Hypothesis tests
Training were given to staff Evaluation of how successful six sigma program is
through measurement of “return vs expense ratio”
Since 2003 Six Sigma is also launched at the Sheraton Hotel in Hong Kong
Six Sigma in Healthcare
Dr. Fugee Tsung, HKUST 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
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: [email protected]
Define
Improve Analyze
MeasureControl