Yun Shen Green Belt

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




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




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


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


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


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


Graduate

Titrator

Analysis

Root cause #2

Root cause #3

Root cause #4

Root cause #1


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


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%


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.


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


Graduate

Titrator

Analysis

Root cause #2

Root cause #3

Root cause #4


Calibration W

ork Instruction

Root cause #1


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


RO

OT C

AU

SE AN

AYLSIS

Graduate

Titrator

Analysis

Root cause #2

Root cause #3

Root cause #4


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 –


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 –


Root cause #2

This P > .05 which m

eans variation is same day to day A

nalysis

37


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 –


Root cause #2

38

Stihl WI –


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 –


Root cause #2

Analysis

40

Solarus Tolerance

Stihl WI –

Calibrate before

use

Original

Linear issueW


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


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


RO

OT C

AU

SED A

NAY

LSIS

Graduate

Titrator

Analysis


before each use

Root cause #2

Root cause #3

Root cause #4


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


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


before each use


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


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


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


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


Conclusion:

Flask calibration did not have any variation from day to day calibration

which m

eans adjustments are not needed.

54

Corrective A


-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



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


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




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


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


Conclusion:

New

calibration improved sigm

a value and move m

ean to “true” value .

59

Stihl WI –

Calibrate

before use

Original Linear

issueW


Root cause #2

Root cause #3

Root cause #4

Error was built

in as volume go

up

Density used

from catalog

given error


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



T-Test of difference = 0 (vs not =): T-Value = 13.96 P-Value = 0.000 D


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


CI for difference: (-0.0020,

0.0527)T-Test of difference = 0 (vs not =): T-Value = 1.90 P-Value = 0.068 D


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.

Engineering

Yun Shen Green Belt