PPT 03 Process Capability and CPK Index

5/20/2018 PPT 03 Process Capability and CPK Index

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Process Capability,Process Capability,Capability Index andCapability Index and6 Sigma6 Sigma

Sanjay Choudhari

Indian Institute of ManagementIndore


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Process Capability

Nominal

value

800 1000 1200

Upper

specification

Loer

specification

Process distribution

!a" Process is capable


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Process Capability

Nominal

value

Upper

specification

Loer

specification

Process distribution

!b" Process is not capable

800 1000 1200


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Process Capability

Loer

specification

#ean

Upper

specification

Si$ si%ma

&our si%ma

'o si%ma

Nominal value


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Process Capability (atio !Cp"

Cp=Upper specification - Lower specification

6

Process Capability RatioProcess Capability Ratio

CP ) 1*++ , Si%ma

CP )2*0 - Si%ma


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Process Capability .nalysis !Cp"

The process is centered at the target of 200 andthe Cp= 2.00. All is well.


7/16


The process has shifted to an average of 205, butCp is still at 2.00.


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Real problems eist !! the process is centered at2"0. #ow, even though Cp = 2.00, much of the

output is defective.


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Process Capability /nde$ !Cp"

Cpk= Minimum of

Upper specification -x

3

x- Lower specification

3,


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Process Capability /nde$ !Cp"


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Problems 1

Upper specification ) 1200 hours

Loer specification ) 800 hours.vera%e life ) 00 hours s ) ,8 hours

Light-bulb Production

Cp)

Upper specification Loer specification

-s



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Problems 1

Upper specification = 1200 hours

Lower specification = 800 hoursAverae !ife = "00 hours = #8 hours

Cp=

1200 - 800

6$#8%


) 1*+

CP ) 1*++ , Si%ma

CP )2*0 - Si%ma



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Problems 1

Upper specification = 1200 hours

Lower specification = 800 hoursAverae !ife = "00 hours = #8 hours

Cp= 1&3"

Cpk= Minimum of

Upper specification -x

3

x- Lower specification

3ProcessProcess

CapabilityCapability

IndexIndex

,



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Problems 1


Loer specification ) 800 hours

.vera%e life ) 00 hours s ) ,8 hours

Cp) 1*+

Cpk) #inimum of

1200 00

+!,8"

00 800

+!,8"

ProcessProcess


IndexIndex

) 0*-

) 2*08



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Problems


Loer specification ) 800 hours.vera%e life ) 00 hours s ) ,8 hours

Cp) 1*+Cpk) 0*-

ProcessProcess


IndexIndex

ProcessProcess


RatioRatio


PPT 03 Process Capability and CPK Index

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