Quality Management 2017

A NALYZE

8. Calculation of the performance indicators

Related to the specifications

Related to the target

Part 1 :

Ppm

Pp

Ppk

Proportion of data out of spec. 

Introduction to SPC

Interval ion Specificat

Dispersion

Dispersion + position

Ppm







2





2

X

target

6



 

Pp  USL

D

USL Min

X X 

LSL

2 1

(



();

)

 6 interval ion Specificat

Ppk





D

3



Pp

Ppm



Part 2 :

2

(91 Pp

)   Ppk

Essential concepts to start with SPC

X

Loss Fonction L = K(X-Target)²

Specification interval

USL Ppk=1.33 Ppk=1.67 Ppk=2.0 USL LSL

Ppk=1.00

USL

LSL.

LSL

D1

Part 3 :

D2

SPC in practice

LSL

Target

Target

Dispersion Ppk 

Dispersion

Dispersion

Ex.:

Ppm < 1

Ex.:

Ppk = 2

Pp = Ppk = 1

Ex.:

Part 4

0.27% out of spec.

Conclusion

✓ Aim: to get indicators as high as possible.

✓ Calculate the three indicators to be able to identify the reason why data are outside the specifications.

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