ch05 slides quality control
TRANSCRIPT
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Chapter 5 1Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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Chapter 5 "Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
Copyright c! "#1" $ohn %iley & Sons, Inc.
Learning Objectives
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Chapter 5 'Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
Copyright c! "#1" $ohn %iley & Sons, Inc.
(asic S)C *ools
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Chapter 5 +Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
Copyright c! "#1" $ohn %iley & Sons, Inc.
- process is operating ith only chance causes of variationpresent is said to
be in statistical control.
- process that is operating in the presence o/ assignable causesis said to beout of control.
5.2 Chance and Assignable Causes of Variation
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Chapter 5 0Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
Copyright c! "#1" $ohn %iley & Sons, Inc.
- control chart contains
- center line -n upper control limit
- lower control limit
- point that plots ithin thecontrol limits indicates theprocess is in control
2o action is necessary - point that plots outside the
control limits is e3idence that theprocess is out o/ control
In3estigation and correcti3eaction are re4uired to /ind andeliminate assignable causes!
*here is a close connectionbeteen control charts andhypothesis testing
5.3 Statistical Basis of the Control Chart
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Chapter 5 7Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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)hotolithography Eample
Important 4uality characteristic in hard ba6e is resist /lo idth
)rocess is monitored by a3erage /lo idth
Sample o/ 5 a/ers
)rocess mean is 1.5 microns
)rocess standard de3iation is #.15 microns
2ote that all plotted points /all inside the control limits
)rocess is considered to be in statistical control
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Determination o/ the Control imits
Chapter 5 8Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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Shehart Control Chart Model
Chapter 5 9Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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:o the Shehart Control Chart %or6s
Chapter 5 1#Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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Chapter 5 11Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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;ut
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Chapter 5 1'Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
Copyright c! "#1" $ohn %iley & Sons, Inc.
More (asic )rinciples
Control charts may be used to estimate processparameters, hich are used to determine capability
*o general types o/ control charts =ariables Chapter 0!
Continuous scale o/ measurement
Quality characteristic described by central tendency and a measureo/ 3ariability
-ttributes Chapter 7! Con/orming>noncon/orming
Counts
Control chart designencompasses selection o/sample si?e, control limits, and sampling /re4uency
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Chapter 5 1+Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
Copyright c! "#1" $ohn %iley & Sons, Inc.
*ypes o/ )rocess =ariability
Stationary anduncorrelated data 3ary around a /ied mean in a stableor predictable manner
Stationaryand autocorrelated successi3e obser3ations are dependentith tendency to mo3e in long runs on either side o/ mean
Nonstationaryprocess dri/ts ithout any sense o/ a stable or /ied mean
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Chapter 5 15Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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@easons /or )opularity
o/ Control Charts
1. Control charts are a pro3en techni4ue /or impro3ing
producti3ity.
". Control charts are e//ecti3e in de/ect pre3ention.
'. Control charts pre3ent unnecessary process
adAustment.
+. Control charts pro3ide diagnostic in/ormation.
5. Control charts pro3ide in/ormation about processcapability.
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Chapter 5 10Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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Chapter 5 17Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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5.3.3 Samle Si!e and Samling "re#uenc$
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Chapter 5 18Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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Chapter 5 19Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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Chapter 5 "#Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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Chapter 5 "1Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
Copyright c! "#1" $ohn %iley & Sons, Inc.
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Chapter 5 "'Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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Chapter 5 "+Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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Chapter 5 "5Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
Copyright c! "#1" $ohn %iley & Sons, Inc.
5.'.+ @ational Subgroups
*he rational subgroupconcept means that subgroups or samples
should be selected so that i/ assignable causes are present, chance /ordi//erences betweensubgroups ill be maimi?ed, hile chance /ordi//erence due to assignable causes withina subgroup ill beminimi?ed.
*o general approaches /or constructing rational subgroups
1. Sample consists o/ units produced at the same time
consecutiveunits )rimary purpose is to detect process shi/ts
". Sample consists o/ units that are representati3e o/ all units producedsince last sample random sample of all process output over samplinginterval ;/ten used to ma6e decisions about acceptance o/ product E//ecti3e at detecting shi/ts to out
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Chapter 5 "0Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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%ational Subgrous
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Chapter 5 "7Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
Copyright c! "#1" $ohn %iley & Sons, Inc.
)attern is 3ery nonrandom in appearance 19 o/ "5 points plot belo the center line, hile only 0 plot
abo3e Bolloing +thpoint, 5 points in a ro increase in
magnitude, a run up *here is also an unusually long run downbeginning ith
18thpoint
5.3.5 &atterns on Control Charts
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Chapter 5 "9Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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*he Cyclic )attern
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Chapter 5 '#Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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Chapter 5 '1Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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5.'.0 Discussion o/ the Sensiti?ing @ules
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Chapter 5 '"Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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1. :istogram or stem
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Chapter 5 ''Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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Check Sheet
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Chapter 5 '+Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
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,areto Chart
C d !ff i
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Chapter 5 '5Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery.
Copyright c! "#1" $ohn %iley & Sons, Inc.
Cause-and-!ffect iagram
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Chapter 5 '0Introduction to Statistical Quality Control 7th Edition by Douglas C Montgomery