Design for six sigma automotive improved gen 4 switchable water pump pulley design , improved design reliability

1. July 2018
By Julian Kalac , P.Eng
Lean Six Sigma Master Black Belt

2. 2
σMethodology that Focuses on Reducing
Process Variation, using data-driven,
measurement-based, statistical methods to Solve
problems, improve performance
σFocus: Surgical “inch-wide, mile-deep”
investigation and resolution
σApproach:
σData driven solves problems at the system and
root cause level
σImplement robust control plans for sustained
improvements
What is “Six Sigma”?
An Analytical Methodology that Focuses on Reducing
Process Variation

4.  DFSS is developed from Six Sigma
 It is methodology to improve product design reliability
 It achieves Six Sigma Level quality (3.4 PPM) by
design,
 DFSS can be used on new product design or to
improve existing product
 DFSS focusses on improving the manufacturing
process capability and roust performance

5. • Robust Design is often synonymous
to “Design for Six Sigma” or
“Reliability-based Optimization.)
• Reliability Analysis
Quantify the reliability (failure
probability, defects per million)
• Robust Design
Optimize the design such that it is
insensitive to unavoidable
uncertainties (e.g. material,loads,…)
• Reliability-based Optimization
Optimize the design such that
reliability is maximized or failure
probability (defects per million) is
minimized
Robust Design is
“Design for Six Sigma”
DFSS

6. Six Sigma = Optimize manufacturing processes such
that they automatically produce parts
conforming with six sigma quality
Design For Six Sigma = Optimize the design such that the parts
conform with six sigma quality, i.e. quality
and reliability are explicit optimization
goals
Design for Six Sigma:
• Achieve “Designed-In”
quality as opposed to
letting customers find
out about quality
problems
• Make informed decision
that are critical to
quality early in the
development process0.1
1
10
100
1000
Research Design Development
PrototypeTests
Production
Product Development Phases
Rel.CostofDesignChange
0%
20%
40%
60%
80%
100%
Design For Six Sigma Six Sigma
DegreeofFredomtoaffect
theProductLifetimeCosts

9.  Define - Voice Of Customers (VOC)
◦ Quality Function Deployment (QFD)
 Measure - Benchmarking
◦ Capability Performance
 Analyze-Process Simulation, Statistical Tolerance Stack Up
 Design- Failure Mode and Effects Analysis (FMEA)
◦ Design Of Experiences (DOE)
 Verify - Statistics Process Control (SPC)


11. SWP --
COMPONEN
T

12.  This device allows the engine the ability to shut off
or limit flow by physically disconnecting the
impeller, thereby achieving fast engine warmup
and improved fuel economy and comfort.

13.  Conventional Water Pump (CWP) –
water pump is belt-driven by engine, with pump speed at a
fixed ratio to engine speed
 Switchable Water Pump (SWP) –
water pump output can be controlled based on the
engine cooling need
 Clutch mechanism to engage/disengage water pump
from the engine
 Can achieve zero-flow, full flow (equivalent of CWP), and
partial flow
 Significant speed up of engine warm-up

14. SWP FUNCTION IS TO:
1. Reduce Engine Warm Up time by blocking coolant
flow
2. Maintain engine Operating temperature 90-95 °C
CUSTOMER REQUIREMENTS TORQUE > 3 Nm)
 Everything mechanical is measured in Nm of Torque
 Component Dims., stack up models, FEA are
designed in Nm Torque

15. SWP design critical to Torque
components
A-PULLEY
B-BELT
C-TENSIONER
D-CLUTCH PACK ASSY
E ELECTRIC COIL
F-ARMATURE
G-HUB
I-FRICTION

16.  SWP was prototyped for VOLVO vehicles which
caused Volvo engines to over-heat
 SWP- failures were discovered by VOLVO during
prototype testing DFMEA was NOT done prior to
Volvo failures
 SWP 2 was launched in production for Chinese
vehicles without a doing a proper Design FMEA
 SWP-3 DFMEA was done after being launched in
production at the request of the Chinese customer

18. High Warranty Failure :
1. 8% of engines overheated in first 2 years of
production
2. SWP unable to support 3Nm Torque
3. Too many Critical Dimensions out of tolerance
4. Contamination Causing Premature Design Failure
5. Grease failure resulting in extreme clutch slip, engine
overheating
6. Clutch unable to disengage causing engine overheating
7. Design FMEA NOT DONE PROPERLY!!
Gen 3 Design failures

19. March 20, 2019
Page 19
Front
Support
Group
Clutch Pack
Magnetic
Group
Main
Support
Group
Rear Rotating
Group

21. DATE CREATED: APRIL 26-2016 REVISION DATE:
Prevention BY DESIGN
Occurrence
Detection BY DESIGN
Detection
Action(s) Taken
Completion Date
Severity
Occurrence
8
100%
µ Coefficienct of friction is smaller
than 0.1
Minimum value of torque calculated at
lowest coefficient of friction of 0.1 is
larger then 3 Nm. 4
Perform 100% of the torque on line for a
minimum of 5 Nm
1 32
Specify on the assy drawing 100%
inspection of transmitted torque.
Implement measurement capability on
assy line.
Roman
Tracz,
MFE
8 4
8
MC
Hub ID larger than Ø79.05 mm.
Hub ID value is Ø79±0.5
Minimum value of torque calculated at
lowest coefficient of friction of 0.1 and
largest hub ID is larger than 3 Nm.
Single point failure value is 80.1 mm.
2
MC analysis shows that the maximum hub
ID is 79.07 mm but failure point is 80.1
mm. As a result probability of failure is
reduced to zero.
2 32
Specify on the part drawing Major
Characteristic.
Inspect dimension at each first off.
Roman
Tracz,
Suppli
er
8 2 1
8
MC
Clutch OD in free state is smaller than
Ø81.2 mm.
Clutch OD value Ø81.35±0.15
Minimum value of torque calculated at
lowest coefficient of friction of 0.1 and
smallest clutch OD of Ø81.2 is larger
than 3 Nm.
Single point failure value is 80.15 mm.
2
MC analysis shows that the minimum
clutch OD is 81.11 mm but failure point is
80.15 mm. As a result probability of failure
is reduced to zero.
2 32
Specify on the part drawing Major
Characteristic.
Inspect dimension at each first off.
Roman
Tracz,
Suppli
er
8 2 1
8
MC
Number of coils smaller than 4.967
Number of coils value is Ø5±0.033
Minimum value of torque calculated at
lowest coefficient of friction of 0.1 and
smallest clutch nr. of coils of 4.967 is
larger than 3 Nm.
Single point failure value is 4.55 coils.
1
MC analysis shows that the minimum
number of coils is 4.95 but failure point is
4.55 coils. As a result probability of failure
is reduced to zero.
1 8
Specify on the assy drawing Major
Characteristic.
Inspect dimension at each first off.
Roman
Tracz,
Suppli
er
8
MC
Armature to EM coil gap smaller than
0.3 mm.
Gap value is 0.4±0.1
Need to determine threshold where the
gap size causes a reduction in
transmitted torque. 10 TBD 10 800
Perform DOE and studies to optimize
the gap.
Refine stak-ups. TBD
8
MC
Staking between driver and bushing
holds less than 5 Nm due to insufficient
no. of teeth on the driver.
Stake holding torque spec 5 Nm MIN.
Analytical simulation difficult. Design
physical tests to determine the
minimum no. of teeth needed on the
driver.
10
Torque to break shall be higher than 5 Nm.
10 800
Design and perform torque tests.
Generate process drawing for the
staking process. Specify stake holding
torque value as a major characteristic.
Roman
Tracz,
MFE
8
Staking between driver and bushing
holds less than 5 Nm due to insufficient
staking step height on the bushing.
Stake holding torque spec 5 Nm MIN.
Analytical simulation difficult. Design
physical tests to determine the
minimum stake step height needed on
the bushing.
10
Torque to break shall be higher than 5 Nm.
10 800
Design and perform torque tests.
Generate process drawing for the
staking process
Roman
Tracz,
MFE
8
MC
Staking between driver and bushing
holds less than 5 Nm due to insufficient
hardness of the driver.
Stake holding torque spec 5 Nm MIN.
Hardness of the driver cannot be
enhanced due to the low carbon
content of the 1010 steel. Increase the
no. of teeth on the driver.
10
Torque to break shall be higher than 5 Nm.
10 800
Design and perform torque tests.
Generate process drawing for the
staking process. Specify stake holding
torque value as a major characteristic.
Roman
Tracz,
MFE
8
MC
Staking between retainer and driver
holds less than 1500 N due to
insufficient staking step height.
Stake axial holding force spec 1500 Nm.
Analytical simulation difficult. Design
physical tests to determine the
minimum stake step height needed on
the bushing.
10
Axial retention force shall be 1500 Nm.
10 400
Design and perform pushout tests.
Generate process drawing for the
staking process. Specify stake pushout
force value as a major characteristic.
Roman
Tracz,
MFE
6
Hub and clutch premature wear.
Nitride layer smaller than 0.01 mm
Nitride layer spec 0.01 to 0.02 mm
Investigate if distinctive color can be
applied to nitride layer.
5
Install color identifying sendor on assembly
line.
2 60
Add colour identification requirement on
drawing.
Install colour identifying sendor on
assembly line.
Roman
Tracz,
MFE
6
Hub and clutch premature wear.
Grease amount less than 1 gr.
Grease amount spec 1 gr MIN.
Investigate if distinctive colour can be
applied to nitride layer.
5
Install colour identifying sendor on
assembly line.
Weigh the clutch subassy before and after
aplying the grease.
2 60
Add colour identification requirement on
drawing.
Install colour identifying sendor on
assembly line.
Weigh the clutch subassy before and
after aplying the grease.
MFE
6
Grease and clutch premature wear.
Hub ID roughness larger than Rz6.3 NONE 10 NONE 10 600
Need more information about the
manufacturing process.
Clutch Pack ASSY
- Transmits torque
from pulley to
impeller as per
customer
specification
(example 3 Nm).
- Enables the
control of pump
states ON/OFF.
Clutch NOT ENGAGED
(impeller speed = 0 RPM)
Component
- Impeller rotates at lower speed
than the pulley
- Extra heat is generated in the
clutch
- Grease degrades at a faster rate
- Clutch ASSY fails prematurely
System
- Coolant flow has lower values
than minimum accepted.
- Engine overheats.
- Vehicle inoperable.
Clutch slips PARTIALLY
(Pulley Speed< impeller
speed < 0 RPM)
Component
- Impeller does not rotate
System
- No coolant flow.
- Engine overheats.
- Vehicle inoperable.
Reduced Clutch Durability
and Life Cycle
Component
- Impeller rotates at lower speed
than the pulley
- Extra heat is generated in the
clutch
- Grease degrades at a faster rate
- Clutch ASSY fails prematurely
System
- Coolant flow has lower values
than minimum accepted.
XXXXXXX
RPN
Litens SWP APQP TeamN/A
Developed by : John Danciu, Julian Kalac DESIGN TEAM: Roman Tracz, Garreth Graves, John Danciu
Potential
Failure
Mode
Key Date:
A c t i o n R e s u l t s
Responsibility
&TargetDate
Part Name,
Number,
Function /
Requirement
Original PFMEA Date:
XXXXXXXX
Recommended Action(s)
Revision Date:
Customer Part No.
Design Failure Mode and Effects Analysis (DFMEA)
Litens Automotive Partnership
LITENS AUTOMOTIVE GROUP
Customer:
Platform Design
Design Responsibility:
N/A N/A
N/A
Subsystem Assembly:
Accessory Drive SWP
Prepared By:Model Year/Vehicle:
XXXXXXX
C U R R E N T D E S I G N C O N T R O L S
Potential
Effect(s) of
Failure
Potential Cause(s) of
Failure
Severity
Classification
DRAFT VERSION
6 CRITICAL
DIMENSIONS
WHY?

22. Pa
ge
22March 20,
EM coil retention concept
EM coil overmold
Anti-Rotation
Features Molded &
Cast-in (matching
draft angles)
* Features are similar
to tensioner insert
bearings

23. Pa
ge
23
2. HUB
- Material : steel 1020
- Mass: 155 g
- Process : stamping
- Machining: see note
- Finish: nitrating
4. Driver shaft
- Material : steel 1020
- Mass: 40 g
- Process : machining
- Machining: see note
- Material : steel 1020
- Mass: 123 g
- Process : stamping
- Machining: see note
5.
Driver
- Material : Music wire
- Mass: 28 g
- Process: Coiling
- Machining: none
7. Wrap spring
- Material : steel 1010
Stanyl TW 271F6
- Mass: 3211 g
- Process :
stampingovermold
- Machining: none
9. ArmatureActuator
8. Retainer
- Material : steel 1020
- Mass: 26 g
- Process: stamping
- Machining: none
10. Grease dam
- Material : Stanyl
TW271F6
- Mass: 4 g
- Process: molding
- Machining: none
Note: indicates machined surfaces.3. Double
row
bearing
- Material : Stanyl 241F6
- Mass: 6 g
- Process : molding
- Machining: none
6.
Carrier
1. Pulley
- Material : steel 1020
- Mass: 430 g
- Process : spinning
- Machining: see note
- Finish: E - coat

24. Failure: SWP TORQUE < 3 Nm if:
1. µ Insufficient friction (Coefficient of friction) Coefficient
of friction =0.138+/-0.01mm---Single Point Failure # 1
2. Insufficient interference between clutch OD and Hub
ID. Min 1.5mm interference required to generate 3 Nm
Torque Single Point Failure # 2
3. Number of clutch coils turns < 4.73 ..Specification = Ø5.0
± 0.033 Single Point Failure # 3
4. Insufficient Armature to EM coil gap < 0.3 mm . Spec =
0.4 +/- 0.1
5. Insufficient Staking force (< 5 Nm) between driver and
bushing
6. Insufficient Lubrication < min 1g/part required
SINGLE POINT FAILURES IDENTIFIED

26. CRITICAL DIMENSIONS
Dimension Nominal Tolerance USL LSL Single Point
Failure
ϭ Torque P-failure Actual Cpk
Coefficienct Friction 0.138 0.01 0.148 0.128 0.116 0.00333 5.1 Nm 0.31 1.001
Hub ID 79 0.05 79.05 78.95 80.15 0.0083 5.1 Nm 0.0036 2.008
Clutch OD 81.35 0.15 81.5 81.2 80.15 0.0375 5.1 Nm 0.82 1.333
Clutch Coil Turns 5 0.03 5.03 4.97 4.2 0.0082 5.1 Nm 0.002 1.220
Nitride Coading 0.015 0.005 0.02 0.01 N/A 0.0083 5.1 Nm 0.201
Coil wire Width 1.6 0.025 1.625 1.575 ? 0.001 5.1 Nm 8.333
Coil wire Width 1.85 0.025 1.875 1.825 ? 0.0016 5.1 Nm 5.208

27. Page 27 March
20, 2019
Probability of SINGLE POINT FAILURE
Dimension
Coefficienct
Friction
Hub ID Clutch OD
Clutch Coil
Turns
X--Nominal 0.138 79 81.35 5
Tolerance 0.01 0.05 0.15 0.03
USL 0.148 79.05 81.5 5.03
LSL 0.128 78.95 81.2 4.97
Failure Point 0.116 80.15 80.15 4.54
(x-Nominal) 0.02 0.05 0.15 0.03
(x-Nominal) sq 0.00 0.00 0.02 0.00
ϭ 0.00 0.01 0.01 0.01
2Ϭ 0.01 0.02 0.02 0.02
e power 0.08 0.15 1.36 0.05
E-power x 1.08 1.16 3.88 1.06
1/2pi 0.16 0.16 0.16 0.16
Probability 0.17 0.19 0.62 0.17
Probability of
FAILURE =
17% 16.8%11.4%

28. Dimension Nominal Tolerance USL LSL Failure Point ϭ USL - LSL Z- % OUT SPEC
Coefficienct
Friction
0.138 0.01 0.148 0.128 0.116 0.003 0.01 3.333 0.0003%
Hub ID 79 0.05 79.05 78.95 80.15 0.0083 0.05 6.024 0.0002%
Clutch OD 81.35 0.15 81.5 81.2 80.15 0.0375 0.15 4.000 0.0250%
Clutch Coil
Turns
5 0.03 5.03 4.97 4.54 0.0082 0.03 3.659 0.0002%

31. Pa
ge
31
VERIFY Design
Design of Experiment
2ⁿ Full Factorial design
GEN 4

32. PURPOSE:
 To find what components significantly impact clutch
torque
METHOD:
 2ⁿ Factorial design
 3 Factors:
1. Coefficient Friction,
2. Clutch OD
3. Hub ID
 Using Torque Stack Up Model

33. March 20, 2019
Page 33
Units
Clutch OD Hub ID Coeff Frict Samples are Replicates Torque-Nm
Random Order A B C A X B A X C B X C A X B X C Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Avg
1 # 6 81.2 82.7 0.1 1 1 1 -1 78.95 80.15 0.1 3.3 3.2 33.14
2 # 8 81.2 82.7 0.148 1 -1 -1 1 78.95 80.15 0.148 8 7.5 34.9496
3 # 1 81.2 82.9 0.1 -1 1 -1 1 78.95 81.5 0.1 2.9 2.8 33.25
4 # 4 81.2 82.9 0.148 -1 -1 1 -1 78.95 81.5 0.148 17.2 18.5 39.2596
5 # 2 82.1 82.7 0.1 -1 -1 1 1 79.5 80.15 0.1 3.3 3 33.21
6 # 5 82.1 82.7 0.148 -1 1 -1 -1 79.5 80.15 0.148 18.2 18.1 39.2196
7 # 3 82.1 82.9 0.1 1 -1 -1 -1 79.5 81.5 0.1 2.9 3 33.4
8 # 7 82.1 82.9 0.148 1 1 1 1 79.5 81.5 0.148 7.8 7.9 35.3696
Factor df Sum of Sq. Mean Sq F p Factor Lo Setting Hi Setting Best
A 1 0.045 0.045 0.0053021 0.95372586 Clutch OD 81.2 82.1 150 -0.5 81.425
B 1 0.0722 0.0722 0.00850693 0.9414483 Hub ID 82.7 82.9 160 -0.4 82.76
A X B 1 8.1608 8.1608 0.96154209 0.50624117 Coeff Frict 0.1 0.148 182 -0.18 0.11968
C 1 31.1986803 31.1986803 3.67596856 0.30605861 Y= 34.63216
A X C 1 0.0032 0.0032 0.00037704 0.98764
B X C 1 0.0032 0.0032 0.00037704 0.98764
A X B X C * * * * *
Error 1 8.4872 8.4872
Total 7 47.9702803
Effect Abs. Effect Rank
Effect of A 0.150 0.150 5
Effect of B 0.190 0.190 4
Effect of C 3.950 3.950 1
Effect of A X B -2.020 2.020 3
Effect of A X C 0.040 0.040 6
Effect of B X C 0.040 0.040 6
Effect of A X B X C -2.060 2.060 2
A LO A HI B LO B HI C LO C HI
35.1498 35.2998 35.1298 35.3198 33.25 37.1996
B LO B HI C LO C HI C LO C HI
A LO 34.0448 36.2548 35.1498 33.195 37.1046 35.1398 33.175 37.0846
A HI 36.2148 34.3848 35.2998 33.305 37.2946 35.3098 33.325 37.3146
A LO B LO
A HI B HI
Enter Factor Names
Effects Table
Use sliders to find best output
Coded level, -2 to 2
ANOVA Table Using the Sample Averages
Select what
you would
like to
optimize Minimum Variation
Target Value
32
33
34
35
36
37
38
Main Effects A, B and C
0.150 0.190
3.950
-2.020
0.040 0.040
-2.060
-3.000
-2.000
-1.000
0.000
1.000
2.000
3.000
4.000
5.000
A B C A X B A X C B X C A X B X C
Pareto of Effects
Factor Lo Setting Hi Setting
Clutch OD 81.2 82.1
Hub ID 82.7 82.9
Coeff Frict 0.1 0.148
-0.5 81.425
-0.4 82.76
-0.18 0.11968
Y= 34.63216
A=Clutch OD
B=Hub ID
C= µ (Coeff Frict)

34. Run
Order
Hub ID
Clutch
OD
µ AxB AxC BxC AxBxC Trial 1 Trial 2
6 78.95 80.15 0.1 1 1 1 -1 3.3 3.2
8 78.95 80.15 0.148 1 -1 -1 1 8 7.5
1 78.95 81.5 0.1 -1 1 -1 1 2.9 2.8
4 78.95 81.5 0.148 -1 -1 1 -1 17.2 18.5
2 79.5 80.15 0.1 -1 -1 1 1 3.3 3
5 79.5 80.15 0.148 -1 1 -1 -1 18.2 18.1
3 79.5 81.5 0.1 1 -1 -1 -1 2.9 3
7 79.5 81.5 0.148 1 1 1 1 15 16
TORQUE Nm

35. March
20, 2019Pa
ge
35
0.150 0.190
3.950
-2.020
0.040 0.040
-2.060
-3.000
-2.000
-1.000
0.000
1.000
2.000
3.000
4.000
5.000
A B C A X B A X C B X C A X B X C
Pareto of Effects
Factor Lo Setting Hi Setting Best
Clutch OD 81.9 82.1 0 -2 81.8
Hub ID 82.7 82.9 100 -1 82.7
Coil Turns 4.5 5.03 260 0.6 4.924
Y= 9.14
Use sliders to find best output
Coded level, -2 to 2
1. Clutch Turns
and
2. Clutch
OD/Hub ID
interaction
influence
final Torque

36. A LO A HI B LO B HI C LO C HI
35.1498 35.2998 35.1298 35.3198 33.25 37.1996
B LO B HI C LO C HI C LO C HI
A LO 34.0448 36.2548 35.1498 33.195 37.1046 35.1398 33.175 37.0846
A HI 36.2148 34.3848 35.2998 33.305 37.2946 35.3098 33.325 37.3146
A LO B LO
A HI B HI
1
Copyright 2010 Dean Christolear
31
32
33
34
35
36
37
38
A LO A HI B LO B HI C LO C HI
Main Effects A, B and C
32.5
33
33.5
34
34.5
35
35.5
36
36.5
A LO A HI
A X B Interaction
B LO
B HI
31
32
33
34
35
36
37
38
A LO A HI
A X C Interaction
C LO
C HI
31
32
33
34
35
36
37
38
B LO B HI
B X C Interaction
C LO
C HI
Interaction between
Clutch OD & Hub ID is
strong
CLUTCH HUB INTERACTION

39. Parameter Gen 4 Gen 3
Preset gap (mm) 0.5 0.4
Force at gap = 0.4 mm (metal to
metal) (N)* 27 38
Steel cost (1.10US$/kg) $ 0.077 $ 0.130
Copper cost (6.28US$/kg) $ 0.226 $ 0.446
Diode cost $ - $ 0.05
COST (steel, copper, resistor, diode) $ 0.303 $ 0.826
Cost saving/pc material only $ (0.52)