yun shen green belt
TRANSCRIPT
1
© M
AHLE
SIX SIG
MA
AN
ALY
SIS O
NC
OM
PRESSIO
N V
OLU
ME
MEA
SUR
MEN
T
YU
N SH
ENA
PRIL 2010
Team:
Don Tobin, Joe Farrell, Pedro D
ondele
2
CA
STING
AN
D C
OM
PRESSIO
N V
OLU
ME
MEA
SUR
EMEN
T LOC
ATION
Define
3Problem
Statement W
orksheet
Specific (create statem
ent from IS portion of Is/Is Not
from the bottom
up)
Reduce custom
er rejections for out of specification compression volum
e on 2-stroke and 4-stroke castings produced at the Trum
bull Plant of the small engine com
ponents division of M
AHLE Engine C
omponents U
SA, Inc.
Measurable (Docum
ent the historical perform
ance and goals)
Rejected parts value over last 3 years w
as $153,146 w
hich is $51,049 per year.The value of parts under custom
er deviation was
$902,835 over 3 years. Sigma value w
as 1.507
Project goal is to reduce the reject value by 50%
, eliminate cause of deviation
requests, and increase sigma value to 6.
Achievable (Validate estimated project
duration and dates with a G
antt chart)End of O
ctober 2010
Relevant (Does your project support any
initiatives? What are the potential savings?)
Supports com
pany goal of “Create savings of $500,000 that is not in the current budget”
with an estim
ated annual saving of $25,000 on rejected parts and $902,835 on potential loss by issued deviation.
Time B
ound (Sponsor date; compare to
Gantt chart for any variances)
End of Novem
ber 2010
Project P
roblem S
tatement
Reduce custom
er rejections for out of specification compression volum
e on 2-stroke and 4-stroke castings produced at the Trum
bull Plant of the small engine com
ponents division of MAH
LE Engine Com
ponents USA, Inc. The target is to reduce
customer rejection cost by 50%
as well as elim
inate the potential for loss caused by deviation requests. The sigma value is
targeted on 6. The project will be com
pleted by end of October 2010 and presented to the custom
er by Decem
ber 2010.
Define
4
Project P
roblem S
tatement
Reduce custom
er rejections for out of specification compression volum
e on 2-stroke and 4-stroke castings produced at the Trum
bull Plant of the small engine com
ponents division of MAH
LE Engine Com
ponents USA, Inc. The target is to reduce
customer rejection cost by 50%
as well as elim
inate the potential for loss caused by deviation requests. The sigma value is
targeted on 6. The project will be com
pleted by end of October 2010 and presented to the custom
er by Decem
ber 2010.
Charter
Project Team
Core
% Tim
eE
xtended%
Time
Yun Shen 20Ed Jones 5
Don Tobin 10
Pedro Fernandes 5
Joe Farrell 5
Pedro Dondele 5
Project Tim
eline
Phase
Est. E
nd Date
Define
4/20/10
Measure
8/30/10
Analyze
9/30/0
Improve
10/30/10
Control
11/30/10
Define
5
Stakeholders (Identify names for each functional area identified)
SuppliersProcess Owners
Customers
Raw materials
2-Stroke casting –Dong Li Ping / IKD Sales
--Dana B/ MTP Purchasing--Klerson M. / MTP Buyer
Incoming inspector:
�Don Tobin
Support:�Yun Shen / Quality Engineer�Marlene M./ Quality Coordinator
Next stepStihl –
Ben/Incoming Inspection
Data & Information
MTP –Klerson M. / Buyer
Downstream
Human Resources
Debbie M. / HRConsum
er
Financial ResourcesTJ / Controller
Regulatory
Key Metrics
Measurable Inputs, xsProcess Metrics, xs and Y
s, ysMeasurable Outputs, Y
s, ys
Compression volum
e standardCom
pression volume m
easurement
Volume specification from
Stihl drawing
Stakeholder Analysis
Define
6C
omm
unication Plan
Com
munication Topic
Audience
PurposeO
wner
Media
Frequency
Toll Gate R
eviews
Sponsor, Finance, M
entors
To ensure all resources and support are provided as w
ell as steer the project in the right direction
Yun Shenppt
End of each D
MA
IC phase
Team M
eetingsC
ore Team
To ensure that all mem
bers understand his/her responses and appropriate feedback
Yun ShenM
eeting notes
Every Month
Extended Team
Meetings
Extended and Core
TeamTo review
project progress Yun Shen
ppt or notes
As requested
Weekly Progress
Report
Define
7SIPO
C
SupplierCustom
erO
utputProcess
Input
•IKD
•Hirschm
ann (Solarus titrator )•M
TP
•Machine bore
•Clean the
casting•M
easure volum
e by using Solarus
titrator•R
ecord the result in report
•Casting
•Volume
Measuring
instrument
•Fixture:1 spark plug•Fixture:2 bore plug
•Stihl•R
eport of result
•Accept or
reject the lot
Define
8
Define Phase: Tollgate R
eview
�D
iscussed Measuring plan w
ith Ed Jones (extended team m
ember
and project advisor)�
Explained the project plan to core team m
embers.
�D
iscussed measuring plan, m
ethods, and time line to core team
m
embers.
�A
rranged test equipment in place to be ready for M
easuring phase.
Define
9H
igh Level Process Map
MA
LHE
Volume
Measure
IKD
Finished C
asting
Ship to Stihl
StihlIncom
inginspection
Ship to MTP
MTP
Incoming
Inspection
Release to
Assem
bly line
Deviation
Return to M
TP
Scrap
Scrap
StihlVolum
eM
easure
IKD
Volum
eM
easure
Deviation
Measure
10
Project Background
High Level Process M
ap shows the supplier, M
TP and customer all have “volum
e m
easure” as a key inspection process. Several questions were raised:
�D
id all three parties use the same m
easuring system?
�H
ow can w
e standardize the measuring system
?�
How
do we justify the rejection is a real representation of a casting defect?
�W
hy are castings rejected by the customer but m
easured as being in specification by M
AH
LE or our supplier?�
Is the measuring system
(instrument) good enough for this volum
e inspection?
Measure
11
Processing Map
Measuring System
Media used in
apparatusProcedure &
Standard
FixtureVerification
Using sam
e Titrator?
Solarus Titrator
Measure
12
Volum
e Measurem
ent Fixtures Verification
�Thread G
auge tube –per Stihl SW
N
43700-01K
ey dimension that affected volum
e:7.7+/-0.2 Zeiss m
easured 7.72(in spec).
�G
auge piston –per Stihl SW
N
43700-01K
ey dimension that affected volum
e38ZD
26 ---81.498( in spec.)*
* Stihl had issues with 38ZD
26
7.7+/-0.2
38ZD26 -81.500+/-0.005
Measure
13
Processing Map
Measuring System
Media used
in apparatusProcedure &
StandardVerify fixture
Using Sam
e Titrator?
Solarus Titrator
Measure
14
Standardized 3 parties measuring system
s. MTP investigated and took actions
to eliminate the variation betw
een IKD
(supplier), MTP(M
EHLE) and
Stihl(customer):
Media used in apparatus
•MTP changed to the
Isopropyl Alcohol that
Stihl (customer) suggested.
We also requested that
IKD
(supplier) do the sam
e.
Procedure &
Standard
•MTP review
ed and adopted custom
er m
easurement standard as
did our suppliers.•M
TP reviewed and re-
calibrated fixtures according to custom
er standard, as w
ell as made
sure our suppliers did the sam
e.
Using Sam
e Titrator?
•IKD
and MTP purchased
same volum
e measuring
instruments (Solarus
Digital Titrator) that Stihl
used.
Measure
15
Processing Map
Measuring System
Media used
in apparatusProcedure &
Standard
Verify fixtureU
sing Same
Titrator? Solaris
Titrator
After standardizing the m
easuring system and elim
inating the above possible variations, w
e had correlation study with our supplier.
Measure
16
5.5
5.6
5.7
5.8
5.9 6
6.1
6.2
6.3
Sample 1
Sample 2
Sample 3
Sample 4
Sample 5
cm³
IKD
–M
TP correlation on Com
pression Volume
46ZD11 FB
wk2/09
USL
LSL
MTP 1
MTP 2
MTP 3
IKD 1
IKD 2
IKD 3
The correlation study show
s there is still had differences am
ong m
easurements after
those corrective actions.
Measure
The result show
s our supplier results still did not correlate with M
TP’s.
17
�R
esults for: 46ZD11 Std cal
��Tw
o-Sample T-Test and C
I: IKD
, MTP
�Tw
o-sample T for IKD
vs MTP
�N
Mean StD
ev SE Mean
�IKD
15 6.0560 0.0473 0.012�
MTP 15 5.8480 0.0330 0.0085
�D
ifference = mu (IKD
) -mu (M
TP)�
Estimate for difference: 0.2080
�95%
CI for difference: (0.1775, 0.2385)
�T-Test of difference = 0 (vs not =): T-Value = 13.96 P-Value = 0.000 D
F = 28�
Both use Pooled StDev = 0.0408
P value is < 0.05 which m
eans the measurem
ents were different.
Measure
Conclusion: There
were still big differences
18
Processing Map
Measuring System
Media used
in apparatusProcedure &
Standard
Verify fixtureU
sing Same
Titrator? Solarus Titrator
At this point, the only other possible cause of variation and error w
as the volum
e measuring instrum
ent (Solarus Titrator) itself.
Measure
19
This project concentrated on the following areas to investigate the root causes and
determine possible solutions:
�D
id this titrator’s original manufacturer’s specification m
eet our volume range
requirement?
�D
id original titrator calibration process contribute to error in the measurem
ent itself , specifically at the low
er potion of instrument range?
�Is there any alternate m
ethod or instrument can be used to m
easure volume?
In order to investigate those possible root causes, a series of experiments w
ere carried out.
Solarus Titrator Measuring System
Analysis
Analysis
20
Solarus Titrator with Stihl
Calibration Work Instruction
Solarus Tolerance
Stihl WI –
Calibrate before use
Original Linear
issueW
eight, density issue
Analysis
Root cause #1
Root cause #2
Root cause #3
Root cause #4
Solarus Titrator Measuring System
Analysis
Root C
auses
21
Procedure of Digital Solarus Titrator
SOLA
RU
S Apparatus
Analytical Balance
Graduated C
ylinder Isopropyl A
lcohol
Solarus Titrator with Stihl C
alibration Work Instruction A
nalysis
22
Procedure of Digital Solarus Titrator
–Fill the graduated cylinder w
ith Isopropyl Alcohol using the SO
LAR
US
titration apparatus to 20ml. R
ecord the SOLA
RU
S digital reading graduated cylinder reading, w
hich is (Apparatus reading A
) = 20ml
–W
eigh the cylinder on the Balance and record the reading as “B
”.–
The specific gravity of Isopropyl Alcohol is 0.786, w
hich is “C”.
–D
ivide “B / C“ to get the resultant “D
”, (D = B/C
). –
Subtract the above value “A” from
“D”, (A
-D). The difference ∆ = A
–D
.–
If ∆ < +/-0.02ml, the apparatus should not be adjusted.
–If ∆ > +/-0.02m
l, following C
alibration instructions as explained above or in the SO
LAR
US Instruction M
anual.
Solarus Titrator with Stihl C
alibration Work Instruction A
nalysis
23
Digital w
eight scale
Tolerance:
100g +/-0.1mg
Graduated Titrator
Tolerance:
10ml +/-0.02
Solarus Digital
Titrator
Tolerance:
5ml +/-0.06
5ml Flask
Tolerance:
5ml+/-0.02
Tolerance of Instruments
Analysis
Root cause #1
124
3
24
Digital Solarus Titrator Specification
�Instrum
ent tolerance is +/-0.06ml
�O
ur cylinders volume ranges are show
n below.
�The instrum
ent tolerance is not fit for these kind of measurem
ents. The tolerance used up alm
ost 1/3 of volume range.
Part #Spec./low
Spec./highR
ange
37ZD6
2.873.27
0.4
38ZD26
3.033.45
0.42
40ZD38
3.573.87
0.3
43ZD1
3.724.16
0.44
46ZD11
5.736.17
0.44
Ave.0.4
Analysis
0.12/0.4=30%
Tolerance of Instruments
Root cause #1
25
This Gage R
& R
Study also shows this instrum
ent is not a good choice.
Part-
to-Part
Reprod
Repeat
Gage R
&R
80
400
Percent
% Contrib
utio
n
% Study Var
0.0
4
0.0
2
0.0
0
Sample Range
_R=
0.0
16
UCL=
0.0
4119
LCL=
0
Don
Joe
Yun
5.0
00
4.9
75
4.9
50
Sample Mean
__X=
4.9
6611
UCL=
4.9
8248
LCL=
4.9
4974
Don
Joe
Yun
10
98
76
54
32
1
5.0
5
5.0
0
4.9
5
Fla
sk__1
Yun
Joe
Don
5.0
5
5.0
0
4.9
5
Operator
10
9 8
7 6
5 4
3 2
1
5.0
00
4.9
75
4.9
50
Fla
sk__1
Average
Don
Joe
Yun
Operator
Gage n
am
e:
D
ate
of s
tudy
:
Reporte
d b
y:
T
ole
rance:
M
isc:
Co
mp
on
en
ts o
f Va
riatio
n
R C
ha
rt by
Op
era
tor
Xb
ar C
ha
rt by
Op
era
tor
S M
ea
su
re b
y F
lask
__
1
S M
ea
su
re b
y O
pe
rato
r
Op
era
tor *
Fla
sk
__
1 I
nte
ractio
n
Ga
ge
R&
R (
AN
OV
A) f
or S
Me
asu
re
Process tolerance = 0.12Study
Var %Study
Var %Tolerance
Source StdDev (SD
) (6*
SD) (%
SV) (SV
/Toler)Total G
age R&
R 0.0110867 0.066520 52.97 55.43
Repeatability 0.0102268 0.061361 48.86 51.13
Reproducibility 0.0042812 0.025687 20.45 21.41
Operator 0.0042812 0.025687 20.45 21.41
Part-To-Part 0.0177538 0.106523 84.82 88.77Total Variation 0.0209311 0.125587 100.00 104.66
This should be < 30%
Analysis
26
Solarus Tolerance
Stihl WI –
Calibrate
before use
Original
Linear issueW
eight, density issue
Graduate
Titrator
Analysis
Root cause #2
Root cause #3
Root cause #4
Root cause #1
Solarus Titrator with Stihl
Calibration W
ork Instruction
We found a G
raduated titrator with a tolerance of
+/-0.02. ( P23 photo #3)
27A
nalysis
Graduate Titrator vs. Solarus D
igital Titrator
Test #1�
Titrated 20 times into 10 pieces 5m
l flasks with each Titrators.
�R
ecorded weighted each flasks by using digital w
eight scale(P23 photo #1) �
Run graphs in M
ini-tab for I-MR
run chart to show variation differences betw
een two Titrators.
�R
un graphs in Mini-tab for F-test to show
different standard deviations of two.
Test #2•
Titrated both Solarus and Graduated Titrators from
1 to 10ml and w
eighted. •
Calculated volum
e from each w
eighted value.•
Calculated error by subtracted it from
instrument face “reading”.
•G
raphed both errors from 1m
l to 10ml scale for both titrators.
Two tests w
ere carried out to approve if the graduated titrator is meet
our measurem
ent requirements.
28
Test 1 result:
�Test for Equal V
ariances: W 3/4/11 versus
Instr.
�95%
Bonferroni confidence intervals for standard
deviations
�Instr. N
Lower StD
ev Upper
�Solarus 20 0.0048930 0.0066788 0.0103474
�Titritor 20 0.0125204 0.0170896 0.0264769
�F-Test (N
ormal D
istribution)�
Test statistic = 0.15, p-value = 0.000�
Levene's Test (Any C
ontinuous Distribution)
�Test statistic = 3.70, p-value = 0.062 A
nalysis
P value is < 0.05 which m
eans 2 population m
eans were different.
Graph also show
Solarus titrator has less variation and errors.
29
The result shows G
raduated titrator has large errors com
pare to Solarus
Test 2 Result
0.0000
0.0100
0.0200
0.0300
0.0400
0.0500
0.0600
0.0700
12
34
56
78
910
Errors
Solarus Vs G
raduated TitratorsTitrated from
1ml to 10m
l
Gradu T
Solarus T
Graduated
TitratorSolarus Titrator
Analysis
30
Two-Sam
ple T-Test and CI: G
-Titrator_1, S-Titrator
Two-sam
ple T for G-Titrator_1 vs S-Titrator
N M
ean StDev SE M
eanG
-Titrator_1 10 0.0375 0.0143 0.0045S-Titrator 10 0.01599 0.00942 0.0030
Difference = m
u (G-Titrator_1) -m
u (S-Titrator)Estim
ate for difference: 0.0214895%
CI for difference: (0.01010, 0.03285)
T-Test of difference = 0 (vs not =): T-Value = 3.97 P-Value = 0.001 D
F = 18B
oth use Pooled StDev = 0.0121
Conclusion:
The Solaris Digital Titrator gives a precise digital reading w
hich results in few
er variations in measurem
ents and is easy to operate.
P value is < 0.05 which m
eans 2 population means w
ere different.G
raph also show Solarus titrator has less variation and errors.
Analysis
31
Solarus Tolerance
Stihl WI –
Calibrate
before use
Original
Linear issueW
eight, density issue
Graduate
Titrator
Analysis
Root cause #2
Root cause #3
Root cause #4
Solarus Titrator with Stihl
Calibration W
ork Instruction
Root cause #1
Solarus Titrator Measuring System
Analysis
Root C
auses
32
Conclusion:
Digital Solarus Titrator is the only choice for us.
Analysis
�Since G
raduated titrator is not a option, so Solarus titrator is our only choice for volum
e inspection.�
Now
we have to focus on potential root causes #2, #3 &
#4.Through follow
ing analysis and experiments w
e may can be able to use
this Digital Solarus Titrator w
ithout or less measurem
ent variations.
33
Solarus Tolerance
Stihl WI –
Calibrate
before use
Original
Linear issueW
eight, density issue
RO
OT C
AU
SE AN
AYLSIS
Graduate
Titrator
Analysis
Root cause #2
Root cause #3
Root cause #4
Solarus Titrator with Stihl
Calibration W
ork Instruction
Root cause #1
34
�In order to investigate this root cause, follow
ing experiment w
as conducted:–
Calibrated Solarus Titrator to Stihl Standard (∆ > +/-0.02m
l) Before
measurem
ents.–
Titrated into 10 pieces 5ML flasks.
–R
ecorded the reading from Solarus digital screen.
–R
un Mini-Tab on I-M
R chart and F-Test.
–R
eviewed charts to see how
this daily calibration influenced to this instrument and
our cylinder measurem
ents.
Stihl WI –
Calibrate before each use
Root cause #2
Test shows each tim
e has to be adjusted. In this case the adjustm
ents were ( 19.93m
l, 20.05ml, &
20.03ml).
According to m
anufacture tolerance (+/-0.06) there is not necessary for any adjustm
ent.
35
2825
2219
1613
107
41
5.05
5.00
4.95
Observation
Individual Value
_X=
4.986
UCL=
5.0474
LCL=
4.9246
2825
2219
1613
107
41
0.075
0.050
0.025
0.000
Observation
Moving Range
__MR=
0.0231
UCL=
0.0755
LCL=
0
5
1
I-MR
Chart of V
- reading
Project: Untitled
Stihl WI –
Calibrate before each use
Root cause #2
It shows process is stable w
ith 3 days std cal.It show
s process is stable with 3 days std cal.
Lab test:Tests w
ere done 3 days 10 parts per day. C
alibrated each day.
Test result:T
he instrument’s
processing is stable after 3 days of m
easurement w
ith daily calibration. W
hich m
eans the instrument tolerance
is +/-0.06, when you calibrated
to +/-0.02 IS NO
T effect to this instrum
ent.
It shows process is stable w
ith 3 days std cal.It show
s process is stable with 3 days std cal.
Analysis
36
std day 3 cal
std day 2 cal
std day 1 cal
0.050.04
0.030.02
0.01
Std cal 3 days
95% Bonferroni Confidence Intervals for StD
evs
Test Statistic1.25
P-Value0.535
Test Statistic0.27
P-Value0.767
Bartlett's Test
Levene's Test
Test for Equal Variances for V
- reading
Project: Untitled
Which m
eans if calibrated before each day or each tim
e use, there are no differences in m
easurement
variation for this instrum
ent.
But the instrum
ent runs inside its control lim
it did not m
ean this daily calibration w
ill not affect the m
easurement if the
same part is m
easured 3 days in a row
according to the follow
ing data.
Stihl WI –
Calibrate before each use
Root cause #2
This P > .05 which m
eans variation is same day to day A
nalysis
37
P value is < 0.05 which m
eans at least 2 population means w
ere different.
One-w
ay AN
OV
A: V
-reading versus Std cal 3 days Source D
F SS MS F P
Std cal 3 days 2 0.006020 0.003010 7.32 0.003Error 27 0.011100 0.000411Total 29 0.017120
S = 0.02028 R-Sq = 35.16%
R-Sq(adj) = 30.36%
Individual 95% C
Is For Mean
Based onPooled StD
evLevel N
Mean StD
ev --------+---------+---------+---------+-std day 1 cal 10 4.9660 0.0241 (--------*-------)std day 2 cal 10 4.9950 0.0165 (--------*--------)std day 3 cal 10 4.9970 0.0195 (-------*--------)
--------+---------+---------+---------+-4.965 4.980 4.995 5.010
Pooled StDev = 0.0203
Individual Value Plot of V
-reading vs Std cal 3 days
Analysis
Stihl WI –
Calibrate before each use
Root cause #2
38
Stihl WI –
Calibrate before each use
2825
2219
1613
107
41
5.05
5.00
4.95
4.90
Observation
Individual Value
_X=4.997
UCL=5.0443
LCL=4.9497
std day 1 calstd day 2 cal
std day 3 cal
2825
2219
1613
107
41
0.100
0.075
0.050
0.025
0.000
Observation
Moving Range
__MR=0.0178
UCL=0.0581
LCL=0
std day 1 calstd day 2 cal
std day 3 cal
I-MR Chart of V- reading by Std cal 3 days
Root cause #2
Analysis
2825
2219
1613
107
41
5.05
5.00
4.95
Observation
Individual Value
_X=4.986
UCL=5.0474
LCL=4.9246
2825
2219
1613
107
41
0.075
0.050
0.025
0.000
Observation
Moving Range
__MR=0.0231
UCL=0.0755
LCL=0
5
1
I-MR Chart of V- reading
Project: Untitled
Chart w
ith stages shows m
ean were different on 3
daysC
hart without stage show
s Titrator runs within
its control limit.
39
Conclusion: C
alibration for each use will contribute to error.
�R
esults show for 3 consecutive days, the instrum
ent has to be adjusted 3 times.
This means sam
e cylinder measured in 3 days w
ill get 3 different readings. The differences of m
ean is 4.997-4.966=0.031 which used up about
0.031/0.4=7.8% of total cylinder volum
e range. 15% of cylinders m
easured out of specification w
ere eventually in specification.�
According to Stihl’s (our custom
er) inspection work instruction, the instrum
ent has to be calibrated before each use.
�W
hen we spoke w
ith the Solaris manufacturer expert, they recom
mended that
the instrument be calibrated only once a year.
Stihl WI –
Calibrate before each use
Root cause #2
Analysis
40
Solarus Tolerance
Stihl WI –
Calibrate before
use
Original
Linear issueW
eight, density issue
RO
OT C
AU
SE AN
AYLSIS
Graduate
Titrator
Analysis
Should not calibrate
before each use
Root cause #2
Root cause #3
Root cause #4
Solarus Titrator with Stihl
Calibration W
ork Instruction
Root cause #1
41
–In order to investigate this root cause, follow
ing experiment w
as conducted:9
Calibrated Solarus Titrator to Stihl standard.
9Titrated 10 tim
es each from 1m
l to 10ml.
9W
eighed each measurem
ent on digital weight scale.
9C
onverted weight to volum
e by using the density rate from Isopropyl
Alcohol supplier (supplier catalog) –
0.785g/ml in this case.
9C
alculated “true” density rate by using 10 measured w
eights–0.781g/m
l in this case.
9Errors as a result of using different density rate are show
n on following
graph.
Original Linear issue
Root cause #3 A
nalysis
42
Conclusion : D
ENSITY
used in calibration increased linear error
The test result shows:
1.The density used for calculation from
w
eight to volume w
as from catalog of
media used in this instrum
ent. It did not reflect true value of this m
edia w
hich introduced error into calibration.
2.The value can be shifted aw
ay up to 0.09 m
l. Which is taking about
0.09/0.4=22.5% of our norm
al m
easuring range.
Analysis
Standard Calibration
-0.1000-0.0800-0.0600-0.0400-0.02000.00000.02000.0400
12
34
56
78
910
scale
Volume error Original Linear issue
Root cause #3
ML
43
Solarus Tolerance
Stihl WI –
Calibrate
before use
Original
Linear issueW
eight, density issue
RO
OT C
AU
SED A
NAY
LSIS
Graduate
Titrator
Analysis
Should not calibrate
before each use
Root cause #2
Root cause #3
Root cause #4
Solarus Titrator with Stihl
Calibration W
ork Instruction
Root cause #1
Error was built
in as volume
went up
44
Weight, density issue
Root cause #4
–In order to investigate this root cause, the follow
ing experiment w
as conducted:9
Calibrated Solarus Titrator to Stihl standard.
9U
sing 10pcs 5ml flasks, three persons each titrated 3 tim
es for each flask. There w
ere a total of 3 people x 3 times x 10 flasks = 90 readings.
9Total 90 readings are show
n on the following graph.
45
5.065.04
5.025.00
4.984.96
4.944.92
LSLUSL
LSL4.94
Target*
USL5.06
Sample M
ean4.96611
Sample N
90StDev(W
ithin)0.0182285
StDev(Overall)
0.020095
Process Data
Cp1.10
CPL0.48
CPU1.72
Cpk0.48
Pp1.00
PPL0.43
PPU1.56
Ppk0.43
Cpm*
Overall Capability
Potential (Within) Capability
PPM < LSL
11111.11PPM
> USL0.00
PPM Total
11111.11
Observed Perform
ancePPM
< LSL76010.42
PPM > USL
0.13PPM
Total76010.55
Exp. Within Perform
ancePPM
< LSL96905.82
PPM > USL
1.49PPM
Total96907.31
Exp. Overall Perform
ance
Within
Overall
Process Capability of S Measure
Weight, density issue
The density rate involved in calibration moved true value from
5.00 ml to 4.966m
l. W
hich used up about 0.034/0.40 = 8.5% of total cylinder volum
e range.
Root cause #4 A
nalysis
Conclusion :
DEN
SITY used in calibration m
oved reading from true value.
46
Solarus Tolerance
Stihl WI –
Calibrate
before use
Original
Linear issueW
eight, density issue
RO
OT C
AU
SED A
NAY
LSIS
Graduate
Titrator
Analysis
Should not calibrate before
each use
Root cause #2
Root cause #3
Root cause #4
Error was built
in as volume go
up
Density used
from catalog
given error
Should not calibrate
before each use
Solarus Titrator with Stihl
Calibration W
ork Instruction
Root cause #1
47
Possible Alternate calibration m
ethods –w
hich do not involve w
eight:1.G
raduated titrator–
This method has been already ruled out because of difficulty of reading
which added extra variations.(A
s shown previously, this is the sam
e reason it is not suitable for daily volum
e inspection).2. Flask m
ight be best option. –
Choose flask size that close to casting volum
e range to minim
ize linear error.
–H
as tighter tolerance +/-0.02.–
No w
eight involved in add on error. –
Easy to operate with less variation.
Improvem
ent
48
Calibrate Solarus Titrator by using Flask
We decided to use 10 pieces 5M
L flasks as calibration tool:1.5 m
L is the closest size available on market and can be easily
replaced if needed. 2.5M
L is close to the our volume m
easuring range.3.It has tight tolerance of +/-0.024.Easy to read.5.V
ery good repeatability ( refer to late gage R&
R study results)
Improvem
ent
49
Procedure for Calibration U
sing Flasks
1.M
easure 10 times for each 5M
L flask.
2.A
verage10 readings.3.
If the average reading > +/-0.02m
L, the adjustment is
requested.4.
Adjustm
ent =(Ave. reading –
5ml)x 4.
5.R
e-measure 10 tim
es for each 5M
L flask again to verify Improvem
ent
50
Solarus Tolerance
Stihl WI –
Calibrate before use
Original Linear
issueW
eight, density issue
RO
OT C
AU
SES AN
D C
OR
REC
TIVE A
CTIO
N
Graduate
TitratorShould not
calibrate before each use
Root cause #2
Root cause #3
Root cause #4
Error was built
in as volume
went up
Density used
from catalog
given error
No need to
calibrate before each use
Improvem
ent
Solarus Titrator with Stihl
Calibration W
ork Instruction
Root cause #1
51
Lab test:1.Solarus Titrator calibrated w
ith new calibration m
ethod (Flask m
ethod). 2. Verified 3 days in a row
by using 5M
L flask. The result:The graph show
s each day result stayed the sam
e. Therefore no adjustm
ents to the instrum
ent is needed.
Improvem
ent
Corrective A
ction to Root cause #2
28
25
2219
16
1310
74
1
5.0
50
5.0
25
5.0
00
4.9
75
4.9
50
Ob
serv
atio
n
Individual Value
_X=
5.003
UC
L=5.03
85
LCL=
4.9675
Day
1D
ay 2
Day
3
28
25
2219
16
1310
74
1
0.0
60
0.0
45
0.0
30
0.0
15
0.0
00
Ob
serv
atio
n
Moving Range
__
MR
=0.0
133
3
UC
L=0.04
356
LCL=
0
Day
1D
ay 2
Day
3
1
1
I-MR
Ch
art o
f Fla
sk C
al_
1 b
y 3
Da
ys
52
Corrective A
ction to Root cause #2
This P > .05 which m
eans variation is same day to day
Improvem
ent
53
Day 3
Day 2
Day 1
5.04
5.03
5.02
5.01
5.00
4.99
4.98
4.97
3 D
ay
s
Flask Cal_1
Bo
xp
lot o
f Fla
sk C
al_
1
One-w
ay ANOVA: Flask Cal_1 versus 3 Days
Source DF SS MS F P3 Days 2 0.000127 0.000063 0.25 0.781Error 27 0.006860 0.000254Total 29 0.006987S = 0.01594 R-Sq = 1.81% R-Sq(adj) = 0.00%
Individual 95% CIs For Mean Based on
Pooled StDevLevel N Mean StDev -----+---------+---------+---------+----Day 1 10 4.9980 0.0175 (--------------*--------------)Day 2 10 5.0010 0.0152 (-------------*--------------)Day 3 10 5.0030 0.0149 (--------------*--------------)
-----+---------+---------+---------+----
4.9910 4.9980 5.0050 5.0120Pooled StDev = 0.0159
P-Value >0.05, which m
eans there are no differences among the 3 days of
measurem
ents.
Improvem
ent
Corrective A
ction to Root cause #2
Conclusion:
Flask calibration did not have any variation from day to day calibration
which m
eans adjustments are not needed.
54
Corrective A
ction to Root cause #3
-0.1000
-0.0800
-0.0600
-0.0400
-0.0200
0.0000
0.0200
0.0400
12
34
56
78
910
With new
Calibration
the error atcylinders volum
e range is < 0.01m
l
Volume Error
Volum
e measured from
1ml to 10m
lN
ew calibration
Old calibration
Improvem
ent
Lab test:1.Solarus Titrator calibrated w
ith new calibration m
ethod (Flask m
ethod). 2. Titrated 10 tim
es from 1m
l to 10m
lThe result:C
ompared to result w
ith old calibrated system
(page 42),the graph show
s with
new calibration m
ethod has less errors. The errors at cylinder volum
e range is < 0.01m
l.
55
Two-Sam
ple T-Test and CI: O
ld Cal, N
ew
Cal
Two-sam
ple T for Old C
al vs New
Cal
N M
ean StDev SE M
eanO
ld Cal 10 -0.0406 0.0330 0.010
New
Cal 10 0.0040 0.0122 0.0039
Difference = m
u (Old C
al) -mu (N
ew C
al)Estim
ate for difference: -0.044695%
CI for difference: (-0.0680, -0.0212)
T-Test of difference = 0 (vs not =): T-Value = -4.00 P-Value = 0.001 D
F = 18Both use Pooled StD
ev = 0.0249
P value is < 0.05 which m
eans 2 population means w
ere different.G
raph also show N
ew calibration has less variation and errors.
Conclusion:
New
calibration method elim
inated error caused by Old calibration
method w
hich involved in weight and density.
Improvem
ent
56
5.065.04
5.025.00
4.984.96
4.94
LSLU
SL
LSL
4.94T
arget*
US
L5.06
Sam
ple Mean
5.00178S
ample N
90S
tDev
(Within)
0.0202207S
tDev
(Ov
erall)0.0200324
Process D
ata
Cp
0.99C
PL
1.02C
PU
0.96C
pk0.96
Pp
1.00P
PL
1.03P
PU
0.97P
pk0.97
Cpm
*
Ov
erall Capability
Potential (W
ithin) Capability
PP
M <
LSL
0.00P
PM
> U
SL
22222.22P
PM
Total
22222.22
Observ
ed Perform
anceP
PM
< LS
L1124.67
PP
M >
US
L1992.59
PP
M T
otal3117.25
Exp. W
ithin Perform
anceP
PM
< LS
L1021.57
PP
M >
US
L1828.08
PP
M T
otal2849.65
Exp. O
verall P
erformance
Within
Overall
Process Capability of F Measure
5.065.04
5.025.00
4.984.96
4.944.92
LSLU
SL
LSL
4.94T
arget*
US
L5.06
Sam
ple Mean
4.96511S
ample N
90S
tDev
(Within)
0.0185274S
tDev
(Ov
erall)0.0205128
Process D
ata
Cp
1.08C
PL
0.45C
PU
1.71C
pk0.45
Pp
0.98P
PL
0.41P
PU
1.54P
pk0.41
Cpm
*
Ov
erall Capability
Potential (W
ithin) Capability
PP
M <
LSL
11111.11P
PM
> U
SL
0.00P
PM
Total
11111.11
Observ
ed Perform
anceP
PM
< LS
L87652.72
PP
M >
US
L0.15
PP
M T
otal87652.87
Exp. W
ithin Perform
anceP
PM
< LS
L110444.19
PP
M >
US
L1.87
PP
M T
otal110446.06
Exp. O
verall P
erformance
Within
Overall
Process C
apability of S M
easure
Improvem
ent
Corrective A
ction to Root cause #4
Lab test:1.Solarus Titrator calibrated w
ith new calibration m
ethod (Flask method).
2. Using 10pcs 5m
l flasks, three persons each titrated 3 times for each flask. There w
ere a total of 3 people x 3 tim
es x 10 flasks = 90 readings. Total 90 readings.The result:C
ompared the result w
ith old calibrated system(page 45), the process capability and T-test
shows sigm
a and standard deviation were im
proved with new
calibration method.
BeforeA
fter
57
�Tw
o-sample T for F M
easure vs S
Measure
��N
Mean S
tDev S
E M
ean�
F Measure 90 5.0018 0.0200
0.0021�
S M
easure 90 4.9651 0.0205 0.0022
���D
ifference = mu (F M
easure) -mu (S
M
easure)�
Estim
ate for difference: 0.03667�
95% C
I for difference: (0.03070, 0.04263)
�T-Test of difference = 0 (vs not =): T-V
alue = 12.13 P-V
alue = 0.000 DF =
178�
Both use P
ooled StD
ev = 0.0203�
S Measure
F Measure
5.08
5.06
5.04
5.02
5.00
4.98
4.96
4.94
4.92
Data
Boxplot of F Measure, S M
easure
P-Value <0.05, which m
eans there are differences between the 2 m
easurements.
Corrective A
ction to Root cause #4
Improvem
ent
Mean is m
ove to target
58
Improvem
ent
DATA
HIG
HLIG
HT
Before
After
Z-Bench (Sigm
a value)1.3
3.16
St Dev
0.0200.017
Mean
4.966114.99989
Corrective A
ction to Root cause #4
Conclusion:
New
calibration improved sigm
a value and move m
ean to “true” value .
59
Stihl WI –
Calibrate
before use
Original Linear
issueW
eight, density issue
Root cause #2
Root cause #3
Root cause #4
Error was built
in as volume go
up
Density used
from catalog
given error
Should not calibrate
before each use
RO
OT C
AU
SES AN
D C
OR
REC
TIVE A
CTIO
NIm
provement
1.Flask Calibration M
ethod2.N
ew W
ork InstructionC
hange Work
Instruction
Root C
auses
Analysis &
A
pprove
Corrective
Actions
60
Items that need to be updated and controlled
MTP im
plemented N
ew C
alibration work
instruction
Training the inspector on new verification
method before each m
easuring.
IKD
(supplier) also implem
ented New
C
alibration method
Updated ISO
system to reflect the new
WI
Continue m
onitoring production and Custom
er returns
Control
61
Changing procedure to correlated to Stihl requirem
ents
∆ > +/-0.02ml
Solarus Titrator calibration procedure
Calibrated before
each use.( Calibrated
at 20ml Solarus
standard)
STIHL
Incoming
inspection∆ > +/-0.02m
l
MA
HLE
new
calibration Method
No change day to day (test
approved). So NO
adjustm
ent needed( New
m
ethod calibrated at 5ml
and our used at around 5ml
area)
MAH
LE New
C
alibration M
ethod
62
After IK
D(supplier) adopted Flask C
alibration method, M
TP and IKD
had correlation study on 37ZD
26. The following results show
s improvem
ent.Before
After
5.5
5.6
5.7
5.8
5.9 6
6.1
6.2
6.3
Sample 1
Sample 2
Sample 3
Sample 4
Sample 5
cm³
46ZD11
Com
pression Volume C
omparison
US
LLSLMT
P 1
MT
P 2
MT
P 3
IKD 1
IKD 2
IKD 3
Control
2.7
2.8
2.9 3
3.1
3.2
3.3
Sample 1
Sample 2
Sample 3
Sample 4
Sample 5
cm³
37ZD26
Com
pression Volume C
omparison
US
LLSL
MT
P 1
MT
P 2
63
Two-Sam
ple T-Test and CI: IK
D, M
TP
Two-sam
ple T for IKD
vs MTP
N M
ean StDev SE M
eanIK
D 15 6.0560 0.0473 0.012
MTP 15 5.8480 0.0330 0.0085
Difference = m
u (IKD
) -mu (M
TP)Estim
ate for difference: 0.208095%
CI for difference: (0.1775, 0.2385)
T-Test of difference = 0 (vs not =): T-Value = 13.96 P-Value = 0.000 D
F = 28Both use Pooled StD
ev = 0.0408
Before
P-Value <0.05, which m
eans measurem
ent results were different betw
een IK
D and M
TP on same cylinders.
Control
64
Two-Sam
ple T-Test and CI: IK
D, M
TP
Two-sam
ple T for IKD
vs MTP
N M
ean StDev SE M
eanIK
D 15 2.9560 0.0400 0.010
MTP 15 2.9307 0.0328 0.0085
Difference = m
u (IKD
) -mu (M
TP)Estim
ate for difference: 0.025395%
CI for difference: (-0.0020,
0.0527)T-Test of difference = 0 (vs not =): T-Value = 1.90 P-Value = 0.068 D
F = 28Both use Pooled StD
ev = 0.0366
After
P-Value >0.05, which m
eans measurem
ent results were sam
e between
IKD
and MTP on sam
e cylinders.
Control
65
YearStihl return/Scrap
Potential Loss(D
eviation Issued)Sigm
a Value
2007$117,456.68
$532,100.003 years average 1.507
2008$1,767.00
$184,500.003 years average 1.507
2009$33,923.13
$186,235.003 years average 1.507
2010$0.00
$0.00Sigm
a value is 6 since IK
D &
MTP adapted new
m
easuring system
Project Goal and Savings:
After M
TP and IKD
adapted the New
calibration system in 2010 there is no
defects found.
66
Summ
ary�
Original Solarus D
igital Titrator has loose tolerance (+/-0.06) and should not be used as a cylinder volum
e inspection tool.�
Stihl (customer) established calibration procedure for calibrating before each use. H
owever, this
method actually contributed m
ore error to daily measurem
ents. �
The original calibration method involved density of m
edia and weight w
hich also contributed to error in m
easurements.
�These errors resulted in false rejections from
our customer and uncorrected adjustm
ent from our
casting supplier, as well as correlation issues am
ong the three parties.�
Since there are no other better instruments available, w
e found a better calibration method and
procedure that eliminated above errors.
�Through this project, w
e approved this new calibration m
ethod that corrected the issue.�
The test data shows that m
easurements w
ere not only close to the “true” value but also correlated w
ell with our supplier’s m
easurements using the sam
e new m
ethod. �
We suggested that Stihl should review
this project and adapt the method to elim
inate all false rejections of com
pression volume m
easurements in future inspections.
67
Lesson Learned:�
How
to apply these quality analysis methods into our daily production issues.
�H
ow to approach the problem
. �
How
to organize and manage the project.
�H
ow to use M
iniTab as a powerful and efficient tool for analyzing data.
�H
ow to determ
ine, step by step, the root cause of the problem.
�H
ow to clearly present results to the audience using such tools as Pow
erPoint.