Gr&r studies

GR & R

1. Carl Zeiss © 2005 Page 1
Gauge R & R
Measurement System Analysis
(MSA)
Br
uce A. Brigham
Prolink Corporation May 16, 2005

2. Carl Zeiss © 2005 Page 2
Carl Zeiss IMT Gauge R & R
Overview
•
Definitions
•
What GR&R Tells You
•
Summary of Terms
•
Measurement System Error
•
How to Conduct a
GR&R
•
Gage R Study (P/T Ratio)
•
Full Gage R & R Study
•
Demonstration of GR&R Software

3. Carl Zeiss © 2005Page 3
Carl Zeiss IMT Measurement System Analysis (MSA)
Definition
A Gage Repeatability and Reproducibility Study is a method of
determining the suitability of a gage or gag
ing system for measuring a
particular process. Every measurement taken has some error
associated with it, and if this error is large compared to the allowable
range of values (the tolerance band), the measuring device will
frequently accept bad parts and reject good ones
1
.
1
MSA Third Edition

4. Carl Zeiss © 2005 Page 4
Carl Zeiss IMT Measurement System Analysis (MSA)
CMMs
The measurement process may be vi
ewed as a man
u
facturi
ng process
that
produces numbers for i
t
s output.
Zeiss Manufactures Data!
Viewing a measurement
system th
is w
ay is useful b
ecause i
t
al
lows us
to br
ing to bear
al
l
the concepts
,
phi
losophies,
and tools that
have
already demonstrated
t
h
eir
usefulness in
the area of
SPC
2
.
2
MSA Third
Edition

5. Carl Zeiss © 2005 Page 5
Carl Zeiss IMT Measurement System Analysis (MSA)
What GR&R Tells You
A Gage Re
peatability and Re
producibility Study conveys 6 basic pieces of
informat
ion.
They are:
•
Part Variation
•
Repeatabil
i
t
y
•
Re
pro
d
u
c
i
bility
•
Re
pe
a
t
a
b
ility and Re
pr
odu
c
i
bility (R
&
R
)
•
Percent of Total Variation
•
Percent of
Tolerance

6. Carl Zeiss © 2005 Page 6
Carl Zeiss IMT Gauge R & R
Measurement System Errors
Can be classified into 5 categories: 1.
Bias –
d
ifference between the observed average and the reference
2.
Stability –
T
he change in bias over time
3.
Linearity –
T
he change in bias over the normal operating range.
4.
Repeatability –
variation in m
easurements obtained with one
measuring instrument used several times by one operator while measuring one part.
5.
Reproducibility –
variation in the average of the measurements
made by different appraisers using the same gage when measuring one part.

7. Carl Zeiss © 2005 Page 7
Carl Zeiss IMT Measurement System Analysis (MSA)
Summary of Terms
Location Variation •
Accuracy –
C
loseness to the tr
ue valu
e
•
Bias –
D
ifference betw
een the observed average and reference
•
Stabil
i
t
y –
The change in
bias over t
i
me
•
Lineari
t
y –
The change in
bias
over the normal operating range
Width Variat
ion
•
Precisi
on –
C
l
o
seness of
rep
eated readings t
o
each other
•
Repeatabil
i
t
y –
var
iat
i
on in
measurements o
b
tained wi
th one CMM
used several
t
i
mes by one operator w
h
i
l
e measuring one part
.
•
Re
producibility –
variation in aver
age of the measurements made
by di
fferent ap
praiser
s using the same CMM measuri
ng one part.
•
GR
R –
t
he
c
o
m
b
ine
d
e
s
t
im
ate
of Re
pe
a
t
a
b
ility
a
nd Re
prod
uc
ibility

8. Carl Zeiss © 2005 Page 8
Carl Zeiss IMT Measurement System Analysis (MSA)
Gage R&
R will Focus on Reporting
Location Variation •••
A
ccuracy
A
ccuracy
A
ccuracy
–––
Closeness to the true value Closeness to the true value Closeness to the true value
•
Bias –
D
ifference betw
een the observed average and reference
•••
Stability Stability Stability
–––
The c
hange in bias over
time
The c
hange in bias over
time
The c
hange in bias over
time
•••
Linearity Linearity Linearity
–––
The c
hange in bias over
t
he normal operating range
The c
hange in bias over
t
he normal operating range
The c
hange in bias over
t
he normal operating range
Width Variat
ion
•
Precisi
on –
C
l
o
seness of
rep
eated readings t
o
each other
•
Repeatabil
i
t
y –
var
iat
i
on in
measurements o
b
tained wi
th one CMM
used several
t
i
mes by one operator w
h
i
l
e measuring one part
.
•
Re
producibility –
variation in aver
age of the measurements made
by di
fferent ap
praiser
s using the same CMM measuri
ng one part.
•
GR
R –
t
he
c
o
m
b
ine
d
e
s
t
im
ate
of Re
pe
a
t
a
b
ility
a
nd Re
prod
uc
ibility

9. Carl Zeiss © 2005 Page 9
Carl Zeiss IMT Measurement System Analysis (MSA)
Measurement System Error

10. Carl Zeiss © 2005 Page 10
Carl Zeiss IMT Measurement System Analysis (MSA)
Gage Study Types Discussed Today
1.
Gage R Study (P/T Ratio)
•
Applications
•
Assumption
s
•
Analy
zed by
2.
Gage R Study (Range Method)
•
Applications
•
Assumption
s
•
Analy
zed by
We will d
i
scu
s
s two meth
ods o
f
testin
g th
e rep
eatability
of th
e CMM. Since CMMs are
differen
t th
an
h
a
n
d
too
l
s, we n
e
ed
differ
en
t so
ftw
are to
sp
eed up th
e testin
g process.

11. Carl Zeiss © 2005 Page 11
Carl Zeiss IMT Measurement System Analysis (MSA)
Gage R St
udy (P/T Ratio)
Application: 1.
Offers a preliminary shor
t term gage repeatability
2.
May be used for screening before shipment of gage
3.
May be used in
pre-production when parts are
min
i
m
a
l
4.
May be used in gage development –
quick comparison
5.
CANNOT be used for final gage acceptance

12. Carl Zeiss © 2005 Page 12
Carl Zeiss IMT Measurement System Analysis (MSA)
Gage R St
udy (P/T Ratio)
Assumptions: 1.
Process stability and variation is not known
2.
Linearity and Bi
as are not Issues
3.
Reproducibility is not considered
4.
The part does not change size during the study
5.
Quick Study with Very Little Time to Perform

13. Carl Zeiss © 2005 Page 13
Carl Zeiss IMT Measurement System Analysis (MSA)
Gage R St
udy (P/T Ratio)
Analyzed by: 1.
Using One Part, One operator, in One Fixture,
2.
Repeatedly Measure the Part 10 or more times.
3.
You may or may not remove the part each time
4.
Calculate Sigma of Measured Values
5.
Multiply
by 6
6.
Divide by Feature Tolera
nce and multiple by 100
7.
Result should be 10% or
less (really 3% or less)

14. Carl Zeiss © 2005 Page 14
Carl Zeiss IMT Measurement System Analysis (MSA)
Gage R St
udy (P/T Ratio)
The wid
t
h o
f
the gag
e
measurements shou
ld
n
o
t
exceed 10%

of th
e to
tal p
art toleran
ce

15. Carl Zeiss © 2005 Page 15
Carl Zeiss IMT Measurement System Analysis (MSA)
Gage R St
udy (P/T Ratio)

16. Carl Zeiss © 2005 Page 16
Carl Zeiss IMT Measurement System Analysis (MSA)
Full Gage R & R Study
Assumptions: 1.
Only 2 factors (appraiser & pa
rts) plus the gage are being
studied.
2.
The effect of variability with
in each part is negligible
3.
There is
no statistica
l inte
raction between appraiser &
parts
4.
The parts
do not change s
i
ze
during the study
5.
Take a lot of Time to Perform

17. Carl Zeiss © 2005 Page 17
Carl Zeiss IMT Measurement System Analysis (MSA)
Full Gage R & R Study
Application: 1.
Offers Long Term Ga
ge Repeatability Study
2.
Determine Appr
aiser Capability
3.
Determine Part Variation
4.
Used for Final Gage Acceptance

18. Carl Zeiss © 2005 Page 18
Carl Zeiss IMT Measurement System Analysis (MSA)
Full Gage R & R Study
Analyzed by: 1.
Use 5 or More Parts and 2 or More Appr
aisers
2.
Each Appr
aiser Measur
es Each Part 2 or More Times
3.
You Must Remove the Part Each Time
4.
Calculate the Full
MSA Calculations

19. Carl Zeiss © 2005 Page 19
Carl Zeiss IMT Measurement System Analysis (MSA)
How to Conduct a
GR&R
1.
Obtain and mark 5-10 parts to be measur
ed by the CMM
2.
Decide how many operators (2 or 3)
will participate
3.
Decide how many trials
(2 or 3) to
measure
4.
Run the QC-CALC GR&R Wizard
5.
Be sure
QC-CALC is
in
the Waiting Screen –
N
o Active File
6.
Run your Calypso part pr
ogram but remember to use the
correct part number and opera
tor displayed in QC-CALC’s
RT Screen.
7.
When the study is complete,
s
e
lect Report –
P
rint Report
8.
Now select Gage Repor
t
Tabular and Print Report

20. Carl Zeiss © 2005 Page 20
Carl Zeiss IMT Measurement System Analysis (MSA)
Begin QC-CALC
GR&R Wizard Demo
Using QC-CALC Real-Time Report

21. Carl Zeiss © 2005 Page 21
Carl Zeiss IMT Measurement System Analysis (MSA)
Full Gage R & R Study

22. Carl Zeiss © 2005 Page 22
Carl Zeiss IMT Measurement System Analysis (MSA)
Full Gage R & R Study

23. Carl Zeiss © 2005 Page 23
Carl Zeiss IMT Measurement System Analysis (MSA)
Full Gage R & R Study

24. Carl Zeiss © 2005 Page 24
Carl Zeiss IMT Measurement System Analysis (MSA)
Full Gage R & R Study

25. Carl Zeiss © 2005 Page 25
Carl Zeiss IMT Measurement System Analysis (MSA)
Full Gage R & R Study

26. Carl Zeiss © 2005 Page 26
Carl Zeiss IMT Measurement System Analysis (MSA)
Full Gage R & R Study

27. Carl Zeiss © 2005 Page 27
Carl Zeiss IMT Measurement System Analysis (MSA)
Full Gage R & R Study

28. Carl Zeiss © 2005 Page 28
Carl Zeiss IMT Measurement System Analysis (MSA)
Full Gage R & R Study

29. Carl Zeiss © 2005 Page 29
Carl Zeiss IMT Measurement System Analysis (MSA)
Full Gage R & R Study

30. Carl Zeiss © 2005 Page 30
Carl Zeiss IMT Measurement System Analysis (MSA)
Full Gage R & R Study

31. Carl Zeiss © 2005 Page 31
Carl Zeiss IMT Measurement System Analysis (MSA)
Full Gage R & R Study

32. Carl Zeiss © 2005 Page 32
Carl Zeiss IMT Measurement System Analysis (MSA)
Full Gage R & R Study

33. Carl Zeiss © 2005 Page 33
Carl Zeiss IMT Measurement System Analysis (MSA)
Full Gage R & R Study

34. Carl Zeiss © 2005 Page 34
Carl Zeiss IMT Measurement System Analysis (MSA)
Full Gage R & R Study

35. Carl Zeiss © 2005 Page 35
Carl Zeiss IMT Measurement System Analysis (MSA)
Full Gage R & R Study

36. Carl Zeiss © 2005 Page 36
Carl Zeiss IMT Measurement System Analysis (MSA)
Full Gage R & R Study

37. Carl Zeiss © 2005 Page 37
Carl Zeiss IMT Measurement System Analysis (MSA)
Full Gage R & R Study
Using QC-CALC SPC Report

38. Carl Zeiss © 2005 Page 38
Carl Zeiss IMT Measurement System Analysis (MSA)
Full Gage R & R Study

39. Carl Zeiss © 2005 Page 39
Carl Zeiss IMT Measurement System Analysis (MSA)
Full Gage R & R Study

40. Carl Zeiss © 2005 Page 40
Carl Zeiss IMT Measurement System Analysis (MSA)
T
h
e calculations circled i
n

red a
r
e show
n as ra
w

values. Th
e secon
d
col
u
mn
is the repe
atability
bas
e
d
on Tota
l Va
ri
a
t
ion. The
third
col
u
mn is repeatabili
ty

based o
n
t
h
e feature
tolerance. The
long s
t
a
nding tra
d
ition
of reportin
g
measurement
error onl
y as a percent of
tolerance is inadequate for the challen
g
es of th
e
marketplace that emp
h
asize
s
t
ra
te
gic
a
n
d c
o
ntinuous

process improvement. MSA

41. Carl Zeiss © 2005 Page 41
Carl Zeiss IMT Measurement System Analysis (MSA)
T
h
e calculations i
n
the
middle co
l
u
mn are the
repeatabili
ty
values based
o
n
t
h
e raw values divided
b
y
the total variation.
See
equati
ons.
View
ing
th
e raw
value for
EV w
e
see 0.
0001093.
B
y

multiply
ing this value by
10
w
e
see that the gage is
usable to measure parts w
i
th tolerances of 0.001

42. Carl Zeiss © 2005 Page 42
Carl Zeiss IMT Measurement System Analysis (MSA)
T
h
e calculations i
n
the rig
h
t
column ar
e the repe
atability

values based on
the t
o
lerance.
T
h
is is a much easier metho
d
of
accepting
the gage for use.
T
h
e GRR i
s
listed a 5.4%
w
h
en
the part tolerance is 0.002. How
e
ver, usi
n
g
these n
u
mbers
can be misleadin
g. As the
custome
r
improve
s
their
process an
d ti
g
h
ten
s
the
tolerance
s
the gage may

become in
adeq
uate for future
projects.

43. Carl Zeiss © 2005 Page 43
Carl Zeiss IMT Measurement System Analysis (MSA)
The Multi-D
i
mension
Gage R & R Stu
d
y
Report
is the same as the lo
n
g

form but allow
s
for 1
0

dimensions per page.

44. Carl Zeiss © 2005 Page 44
Carl Zeiss IMT Measurement System Analysis (MSA)
Demonstration
This is the end of the PowerPoint Presentation
We will now use QC-CA
L
C to demonstrate GRR
.