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Statistical Process Control
Using Control Charts to Monitor
Quality
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Walter Shewhart
www.york.ac.uk/.../ histstat/people/welcome.htm
Developer of Control Charts in the late 19!"s
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Statistical Process Control
# SPC does notrefer to a particulartechni$ue% algorith& or
proce'ure
# SPC is anoptimisation philosophyconcerne' with continuous
processimprovements% using a collection of(statistical) tools
for
* 'ata an' process analysis* &a+ing inferences a,out process
,ehaviour
* 'ecision &a+ing
http-..lorien/ncl/ac/u+.&ing.spc.spc1/ht&
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Ultimately, SPC seeks to
maximize profitby:
# i&proving pro'uct $uality
# i&proving pro'uctivity
# strea&lining process
# re'ucing wastage
# re'ucing e&issions# i&proving custo&er service%
etc/
http-..lorien/ncl/ac/u+.&ing.spc.spc1/ht&
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Control Charts
# Control charts are particularly useful for
&onitoring $uality an' giving early warnings
that a process &ay ,e going 0ut of Control
an' on its way to pro'ucing 'efective parts/
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http-..www/p$syste&s/co&.pro'ucts.SPC.C234runner.C234runnerCharting56a&ple1/php
http://www.pqsystems.com/products/SPC/CHARTrunner/CHARTrunnerChartingExample1.phphttp://www.pqsystems.com/products/SPC/CHARTrunner/CHARTrunnerChartingExample1.phphttp://www.pqsystems.com/products/SPC/CHARTrunner/CHARTrunnerChartingExample1.php
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0,7ectives
# 8e a,le to e6plain how control charts
relate to assigne' 'i&ension an'
tolerance
# State what value you get fro& control
charts
# 8e a,le to na&e several ways that control
charts in'icate that a process is out of
control
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or&al Distri,utionDefine' ,y two para&eters-
&ean an' stan'ar' 'eviation
http-..www/ca&p,ell/,erry/e'u.faculty.7grout.spclecture/ppt
Reminder:
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/:!!/!:
Example:
Suppose we specify a 'i&ension
an' tolerance as shown/
uestions:
; What 'oes the control chart loo+ li+e
