D M A I C

Define Measure Analyze Improve Control

D

Define

M

Measure

A

Analyze

I

Improve

C

Control

Implementing Six Sigma Quality
at Better Body Manufacturing

2

D M A I C

Define Measure Analyze Improve Control

Dimension

DPM

ASM_7Y

172475

ASM_8Y

85824

ASM_3Y

19786

ASM_9Y

3874

ASM_10Y

776

ASM_6Y

4

Overview

ABC Incorporated (ABC) is not achieving Six Sigma quality levels
for all critical Body-Side Sub-Assembly dimensions as requested by
their customers.

Ensure that all critical body-side subassembly dimensions are
within Six Sigma quality levels of  3.4 DPM. C

p

2.0 and C

pk

1.67.

• Change tonnage to > 935 to correct ASM_7Y and

ASM_8Y

• Set clamp position to location 2 for ASM_9Y and

ASM_10Y

• Re-machine A-pillar die to correct A_3Y and

ASM_3Y

• Determined the correlation between body side and assembly

dimensions.

• Evaluated the significance of Tonnage > 935 for ASM_7Y &

ASM_8Y.

• Conducted a DOE for Clamp position for ASM_9Y & ASM_10Y.

0

50000

100000

150000

200000

A

S

M

_7

Y

A

S

M

_8

Y

A

S

M

_3

Y

A

S

M

_9

Y

A

S

M

_1

0

Y

A

S

M

_6

Y

DPM

3

D M A I C

Define Measure Analyze Improve Control

Problem Statement & The

Goal

ABC Incorporated’s customer wants ABC to apply Six Sigma problem
solving methodology to insure that the body side subassembly is
achieving Six Sigma quality levels of less than 3.4 defects per million
for all critical body side subassembly dimensions.

ABC needs an improvement strategy that minimizes the rework costs
while achieving the desired quality objective. ABC’s goal is to produce
module subassemblies that meet the customer requirements and not
necessarily to insure that every individual stamped component within
the assembly meets it original print specifications – sub-system
optimizations vs. local optimization.

+

+

A-Pillar

Reinforcement

B-Pillar

Reinforcement

Body Side Outer

+

+

A-Pillar

Reinforcement

B-Pillar

Reinforcement

Body Side Outer

D

Define

4

D M A I C

Define Measure Analyze Improve Control

Measure Phase

Key Variables:

Assembly process variables:
Weld Pattern (density), Clamp Location, and Clamp Weld
Pressure
Stamping process variables (body side):
Press Tonnage, Die Cushion Pressure, Material Thickness

Body Assembly Dimensions ASM_1Y through ASM_10Y

M

Measure

4

776

172475

85824

19786

3874

0

50000

100000

150000

200000

ASM_7Y

ASM_8Y

ASM_3Y

ASM_9Y

ASM_10Y

ASM_6Y

DPM

Assembly Dimensions with Highest
Defects

5

D M A I C

Define Measure Analyze Improve Control

Resolution alternatives (based upon past experience):

1. Make adjustments to assembly process settings
2. Reduce variation of components through better control of
stamping
process input variables
3. Rework stamping dies to shift component mean deviation that
is off
target and causing assembly defects

Target Performance Level:

All ten critical assembly dimensions at Six Sigma quality level of
 3.4 DPM.
C

p

2.0 and C

pk

1.67

Fish Bone and P-Diagrams:

Understanding potential causes of defects. From this we pick the
assembly and component dimensions that require further analysis

Analyze Phase

A

Analyze

6

D M A I C

Define Measure Analyze Improve Control

For our analysis we will do a DOE to
check for levels that contribute to
better quality product.

Weld Pattern
(density)

Clamp
Location

Operator

Machine

Materials

Methods

Clamp Weld
Pressure

Press
Tonnage

Die Cushion
Pressure

Material
Thickness

Training

Yield
Strength

Elastic
Limit

Environment

Temperature

Humidity

Quality

Component
Variability

Inspection
Process

Gage R&R

Body
Assembly

Analyze Phase

A

Analyze

Body Side Sub-Assembly

Stamping Process

Outputs

Body Side Sub-Assemblies at

Six Sigma quality levels

Control Variables

Clamp Location Press
Tonnage
Weld Density Die Pressure
Clamp Pressure

Error
States

Dimensional
defects

Noise Variables

Environment
Inherent Variation

Inputs

Material Thickness

Yield Strength

7

D M A I C

Define Measure Analyze Improve Control

Analysis of ASM_7Y and ASM_8Y

Analyze Phase

A

Analyze

Conclusion: BS_7Y and ASM_7Y are following a
similar trend.
A correlation chart to study this further shows high
correlation.
(Pearson correlation, R of 0.701).

8

D M A I C

Define Measure Analyze Improve Control

Analyze Phase

A

Analyze

Capability of
B_7Y

698416 DPM

0 DPM

Conclusion: B_7Y has 0 ppm compared
to ~700K DPM in BS_7Y.
Furthermore, BS_7Y shows strong
correlation on dimension ASM_7Y.
(Pearson correlation, R of 0.786).

Capability of
BS_7Y

9

D M A I C

Define Measure Analyze Improve Control

XY Plot of Tonnage vs. BS_7Y

Conclusion: Tonnage values above 935 greatly improves BS_7Y
and brings it closer to the mean. Let’s see what impact this has on
ASM dimensions 7Y, 8Y, 9Y, and 10Y by creating a subset of the
data looking only at Tonnage > 935.

Analyze Phase

A

Analyze

10

D M A I C

Define Measure Analyze Improve Control

Analyze Phase

A

Analyze

-1.0

-0.5

0.0

0.5

1.0

LSL

USL

Capability Analysis of ASM_7Y at Tonnage > 935

USL
Target
LSL
Mean
Sample N
StDev (Within)
StDev (Overall)

Cp
CPU
CPL
Cpk

Cpm

Pp
PPU
PPL
Ppk

P PM < LSL
P PM > USL
P PM Total

PPM < LSL
PPM > USL
PPM Total

PPM < LSL
PPM > USL
PPM Total

1.00

*

-1.00

0.09

12

0.163174
0.147855

2.04
1.86
2.23
1.86

*

2.25
2.05
2.46
2.05

0.00
0.00
0.00

0.00
0.01
0.01

0.00
0.00
0.00

Process Data

Potential (Within) Capability

Overall Capability

Observed Performance

Exp. "Within" P erformance

Exp. "Overall" Performance

Within

Overall

-1.0

-0.5

0.0

0.5

1.0

LSL

USL

Capability Analysis of ASM_8Y at Tonnage > 935

USL
Target
LSL
Mean
Sample N
StDev (Within)
StDev (Overall)

Cp
CPU
CPL
Cpk

Cpm

Pp
PP U
PP L
Ppk

PPM < LSL
PPM > USL
PPM Total

PPM < LSL
PPM > USL
PPM Total

PP M < LSL
PP M > USL
PP M Total

1.00000

*

-1.00000
-0.12833

12

0.101825
0.089161

3.27
3.69
2.85
2.85

*

3.74
4.22
3.26
3.26

0.00
0.00
0.00

0.00
0.00
0.00

0.00
0.00
0.00

Process Data

Potential (Within) Capability

Overall Capability

Observed Performance

Exp. "Within" Performance

Exp. "Overall" Performance

Within

Overall

-1.0

-0.5

0.0

0.5

1.0

LSL

USL

Capability Analysis of ASM_9Y at Tonnage > 935

USL
Target
LSL
Mean
Sample N
StDev (Within)
StDev (Overall)

Cp
CPU
CPL
Cpk

Cpm

Pp
PPU
PPL
Ppk

P PM < LSL
P PM > USL
P PM Total

PPM < LSL
PPM > USL
PPM Total

PPM < LSL
PPM > USL
PPM Total

1.00000

*

-1.00000

0.52083

12

0.206010
0.177098

1.62
0.78
2.46
0.78

*

1.88
0.90
2.86
0.90

0.00
0.00
0.00

0.00

10010.77
10010.77

0.00

3408.51
3408.51

Process Data

Potential (Within) Capability

Overall Capability

Observed Performance

Exp. "Within" P erformance

Exp. "Overall" Performance

Within

Overall

-1.0

-0.5

0.0

0.5

1.0

LSL

USL

Capability Analysis of ASM_10Y at Tonnage > 935

USL
Target
LSL
Mean
Sample N
StDev (Within)
StDev (Overall)

Cp
CPU
CPL
Cpk

Cpm

Pp
PP U
PP L
Ppk

PPM < LSL
PPM > USL
PPM Total

PPM < LSL
PPM > USL
PPM Total

PP M < LSL
PP M > USL
PP M Total

1.00

*

-1.00

0.39

12

0.215541
0.187663

1.55
0.94
2.15
0.94

*

1.78
1.08
2.47
1.08

0.00
0.00
0.00

0.00

2326.72
2326.72

0.00

576.00
576.00

Process Data

Potential (Within) Capability

Overall Capability

Observed Performance

Exp. "Within" Performance

Exp. "Overall" Performance

Within

Overall

Conclusion: Setting Tonnage to greater than 935 resulted in
ASM_7Y and ASM_8Y meeting the goal of <3.4 DPM. ASM_9Y and
ASM_10Y require further analysis.

Impact this has on ASM dimensions 7Y, 8Y, 9Y & 10Y on Tonnage

11

D M A I C

Define Measure Analyze Improve Control

DOE for Response Variable ASM_9Y

• DOE factorial analysis shows Clamp Position is the only
significant factor in
determining ASM_9Y dimension

 
DOE Response Optimization for ASM_9Y

• Set Clamp Position to Location 2 (level 1)
• Optimizer recommends setting Weld Density to 1.33 weld per
inch (level 1),
but this appears to be a robust parameter, which could be
changed for the benefit
of process without reducing quality if processing time or cost
shows a benefit.
• Optimizer recommends setting Clamp Pressure to 2100 psi (level
1), but this
appears to be a robust parameter, which could be changed for
the benefit of process
without reducing quality if processing time or cost shows a
benefit.
• Run additional tests at recommended settings to confirm results
• Weld Density and Clamp Pressure are robust parameters and
can be set to optimize
the process capability to maximum level and lowest cost.

Analyze Phase

A

Analyze

Input Variable

Proposed ASM_9Y Setting Proposed ASM_10Y Setting

Clamp Location

Location 2

Location 2

Weld Density (welds per X inches)

1.33

1.33

Clamp Pressure

2100 psi

2100 psi

12

D M A I C

Define Measure Analyze Improve Control

Analyze Phase

A

Analyze

DOE for Response Variable ASM_10Y

• DOE factorial analysis shows Clamp Position is also the only
significant
factor in determining ASM_10Y dimension

 
DOE Response Optimization for ASM_10Y

• Setting clamp to location 2 also improves ASM_10Y
• Recommend same settings used to improve ASM_9Y to improve
process
capability which also allows for no changes to machine setup and
helps reduce
possible process concerns
• Run additional tests at recommended settings to confirm results
• Weld Density and Clamp Pressure are robust parameters and can
be set to optimize
the process capability to maximum level and lowest cost.

13

D M A I C

Define Measure Analyze Improve Control

DOE for Response Variable ASM_3Y

• DOE factorial analysis shows that no factors are significant
• Response Optimization shows no solution for response
optimizer

Observe Process Capability of A_3Y and BS_3Y

• ASM_3Y and A_3Y have a similar mean shift in the -Y
direction

Correlation of Output Variables

• No dimensional correlations appear to exist between
ASM_3Y and
A_3Y or BS_3Y

Stepwise Regression Analysis of BS_3Y

• Tonnage and Die Pressure appear to be significant in
determining
dimension BS_3Y
• Tonnage values < 920 may improve BS_3Y
• Die Pressure appears to have no clear correlation to
BS_3Y

Analyze Phase

A

Analyze

14

D M A I C

Define Measure Analyze Improve Control

Process Capability of BS_ 3Y and ASM_3Y at Tonnage < 920

• Created subset of body data looking only at dimensions with
Tonnage < 935

• Tonnage < 920 appears to improve the mean of BS_3Y slightly,
but has no
impact on improving the mean of ASM_3Y.

-1.0

-0.5

0.0

0.5

1.0

LSL

USL

Capability Analysis of ASM_3Y

USL
Target
LSL
Mean
Sample N
StDev (Within)
StDev (Overall)

Cp
CPU
CPL
Cpk

Cpm

Pp
PPU
PPL
Ppk

PPM < LSL
PPM > USL
PPM Total

PPM < LSL
PPM > USL
PPM Total

PPM < LSL
PPM > USL
PPM Total

1

*

-1

0

36

0.0851436
0.0971725

3.91
3.91
3.91
3.91

*

3.43
3.43
3.43
3.43

0.00
0.00
0.00

0.00
0.00
0.00

0.00
0.00
0.00

Process Data

Potential (Within) Capability

Overall Capability

Observed Performance

Exp. "Within" Performance

Exp. "Overall" Performance

Within

Overall

Die remachined to move mean +0.80

Capability of A_3Y and ASM_3Y with
+0.80 mm mean offset

• Manipulate data for A_3Y and
ASM_3Y by +0.80 mm to simulate
re-machining

• Process capability shows 0
defects for A_3Y and ASM_3Y with
this mean offset

Analyze Phase

A

Analyze

15

D M A I C

Define Measure Analyze Improve Control

Analyze Phase

A

Analyze

Conclusions

• From the analysis of ASM_7Y and ASM_8Y we can conclude
that:

•

Setting tonnage > 935 results in ASM_7Y and ASM_8Y

meeting the goal

• Analyzing ASM_9Y and ASM_10Y helps determine that:

•

Setting clamp position to location 2, weld density to 1 weld

every 1.33”
and clamp pressure to 2000 psi helps with dimensions
ASM_9Y and
ASM_10Y

• Analyzing ASM_3Y helps us conclude that:

•

Re-machine A-Pillar die to move A_3Y to nominal – which

could cause
BS_3Y to shift towards nominal – effectively shifting ASM_3Y
to nominal

16

D M A I C

Define Measure Analyze Improve Control

With the recommended changes the process performance will
improve significantly

Dimension Mean

StDev
Overall

DPM_Obsv DPM_Within DPM_Exp

P

p

P

pk

C

p

C

pk

ASM_1Y

-0.035

0.165

0

0

0

2.01

1.94

2.47

2.39

ASM_2Y

0.259

0.152

0

0

1

2.20

1.63

2.31

1.71

ASM_3Y

0.000

0.097

0

0

0

ASM_4Y

0.009

0.115

0

0

0

2.90

2.87

3.53

3.50

ASM_5Y

-0.330

0.145

0

0

2

2.30

1.54

3.72

2.50

ASM_6Y

-0.284

0.160

0

1

4

2.08

1.49

2.24

1.60

ASM_7Y

0.090

0.148

0

0

0

2.25

2.05

2.04

1.86

ASM_8Y

-0.128

0.089

0

0

0

3.74

3.26

3.27

2.85

ASM_9Y

0.521

0.180

0

0

0

ASM_10Y

0.395

0.191

0

0

0

A

Analyze

Analyze Phase

17

D M A I C

Define Measure Analyze Improve Control

Recommendations for improving the process:

•

Set Tonnage to above 935 to improve ASM_7Y & ASM_8Y

•

Set Clamp to Location 2 to improve ASM_9Y & ASM_10Y

•

Re-machine the A-Pillar die to move the mean of A_3Y to

nominal which in turn will move ASM_3Y to nominal

Implement the above recommendations and run additional samples to
verify results.

I

Improve

Improve Phase

18

D M A I C

Define Measure Analyze Improve Control

Control Phase

C

Control

Recommended controls :

•

Implement a gauge on the body side component press to

monitor tonnage

•

Implement an alarm and shut-off feature on the body side press

if tonnage
falls below 935 tons

•

Implement poke-yoke clamping fixture that ensures clamp is

always in
Position 2

•

Establish an affordable control plan for ongoing monitoring of

the 10
critical assembly dimensions.

19

D M A I C

Define Measure Analyze Improve Control

Summary

ABC Incorporated is not achieving Six Sigma quality levels for all
critical Body-Side Sub-Assembly dimensions as requested by their
customers. BBM needs to apply Six Sigma problem solving
methodology to establish an improvement strategy that minimizes
rework costs, yet achieves the desired quality objective.

•

Implement a gauge on the body side component press to monitor

tonnage

•

Implement an alarm & shut-off feature on body side press if

tonnage falls below 935

•

Implement poke-yoke clamping fixture that ensures clamp is always

in Position 2

•

Establish control plan for ongoing monitoring of the 10 critical

assembly dimensions.

•

Set Tonnage to above 935 to improve ASM_7Y & ASM_8Y

•

Set Clamp to Location 2 to improve ASM_9Y & ASM_10Y

•

Re-machine the A-Pillar die to move the mean of A_3Y to

nominal

Bring the key process output variables within Six Sigma quality
level of  3.4 DPM.

C

p

2.0 and C

pk

1.67