ch05 slides quality control

7/24/2019 ch05 slides quality control

1/36

Chapter 5 1Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery.

Copyright c! "#1" $ohn %iley & Sons, Inc.


2/36

Chapter 5 "Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery.


Learning Objectives


3/36

Chapter 5 'Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery.


(asic S)C *ools


4/36

Chapter 5 +Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery.


- 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


5/36


6/36



- 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


7/36



)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


8/36

Determination o/ the Control imits




9/36

Shehart Control Chart Model




10/36

:o the Shehart Control Chart %or6s

Chapter 5 1#Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery.



11/36




12/36

;ut


13/36

Chapter 5 1'Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery.


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


14/36

Chapter 5 1+Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery.


*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


15/36



@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.


16/36



'


17/36



5.3.3 Samle Si!e and Samling "re#uenc$


18/36




19/36




20/36

Chapter 5 "#Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery.



21/36

Chapter 5 "1Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery.



22/36


23/36

Chapter 5 "'Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery.



24/36

Chapter 5 "+Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery.



25/36



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


26/36



%ational Subgrous


27/36



)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


28/36


29/36



*he Cyclic )attern


30/36

Chapter 5 '#Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery.



31/36

Chapter 5 '1Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery.


5.'.0 Discussion o/ the Sensiti?ing @ules


32/36

Chapter 5 '"Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery.


1. :istogram or stem


33/36

Chapter 5 ''Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery.


Check Sheet


34/36

Chapter 5 '+Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery.


,areto Chart

C d !ff i


35/36

Chapter 5 '5Introduction to Statistical Quality Control, 7th Edition by Douglas C. Montgomery.


Cause-and-!ffect iagram


36/36

Chapter 5 '0Introduction to Statistical Quality Control 7th Edition by Douglas C Montgomery

ch05 slides quality control

Documents