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D M A I CDefine Measure Analyze Improve Control

DDefine

MMeasure

AAnalyze

IImprove

CControl

Implementing Six Sigma Qualityat Better Body Manufacturing

2


Dimension DPMASM_7Y 172475ASM_8Y 85824ASM_3Y 19786ASM_9Y 3874ASM_10Y 776ASM_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. Cp 2.0 and Cpk 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

AS

M_7

Y

AS

M_8

Y

AS

M_3

Y

AS

M_9

Y

AS

M_1

0Y

AS

M_6

Y

DPM

3


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-PillarReinforcement

B-PillarReinforcementBody Side Outer

++

A-PillarReinforcement

B-PillarReinforcementBody Side Outer

DDefine

4


Measure Phase

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

Body Assembly Dimensions ASM_1Y through ASM_10Y

MMeasure

4776

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


Resolution alternatives (based upon past experience): 1. Make adjustments to assembly process settings2. Reduce variation of components through better control of stamping process input variables3. 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. Cp 2.0 and Cpk 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 AAnalyze

6


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

Weld Pattern (density)

Clamp Location

Operator

MachineMaterialsMethods

Clamp Weld Pressure

Press Tonnage

Die Cushion PressureMaterial

Thickness

Training

Yield Strength

Elastic Limit

Environment

Temperature

Humidity

Quality Component Variability

Inspection Process Gage R&R

Body Assembly


Body Side Sub-AssemblyStamping Process

OutputsBody Side Sub-Assemblies at

Six Sigma quality levels

Control VariablesClamp Location Press TonnageWeld Density Die Pressure Clamp Pressure

Error StatesDimensional defects

Noise VariablesEnvironmentInherent Variation

InputsMaterial Thickness

Yield Strength

7


Analysis of ASM_7Y and ASM_8Y


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



Capability of B_7Y

698416 DPM0 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


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.


10



-1.0 -0.5 0.0 0.5 1.0

LSL USL

Capability Analysis of ASM_7Y at Tonnage > 935

USLTargetLSLMeanSample NStDev (Within)StDev (Overall)

CpCPUCPLCpk

Cpm

PpPPUPPLPpk

PPM < LSLPPM > USLPPM Total



1.00 *

-1.00 0.09

120.1631740.147855

2.041.862.231.86

*

2.252.052.462.05

0.000.000.00

0.000.010.01

0.000.000.00

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



CpCPUCPLCpk

Cpm

PpPPUPPLPpk




1.00000 *

-1.00000-0.12833

120.1018250.089161

3.273.692.852.85

*

3.744.223.263.26

0.000.000.00

0.000.000.00

0.000.000.00

Process Data



Within

Overall

-1.0 -0.5 0.0 0.5 1.0

LSL USL



CpCPUCPLCpk

Cpm

PpPPUPPLPpk




1.00000 *

-1.00000 0.52083

120.2060100.177098

1.620.782.460.78

*

1.880.902.860.90

0.00 0.00 0.00

0.0010010.7710010.77

0.00 3408.51 3408.51

Process Data



Within

Overall

-1.0 -0.5 0.0 0.5 1.0

LSL USL



CpCPUCPLCpk

Cpm

PpPPUPPLPpk




1.00 *

-1.00 0.39

120.2155410.187663

1.550.942.150.94

*

1.781.082.471.08

0.00 0.00 0.00

0.002326.722326.72

0.00 576.00 576.00

Process Data



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


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.


Input Variable Proposed ASM_9Y Setting Proposed ASM_10Y SettingClamp Location Location 2 Location 2Weld Density (welds per X inches) 1.33 1.33Clamp Pressure 2100 psi 2100 psi

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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


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


14


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


CpCPUCPLCpk

Cpm

PpPPUPPLPpk




1 *-1 0

360.08514360.0971725

3.913.913.913.91

*

3.433.433.433.43

0.000.000.00

0.000.000.00

0.000.000.00

Process Data



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


15



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


With the recommended changes the process performance will improve significantlyDimension Mean StDev

OverallDPM_Obsv DPM_Within DPM_Exp Pp Ppk Cp Cpk

ASM_1Y -0.035 0.165 0 0 0 2.01 1.94 2.47 2.39ASM_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 3.50ASM_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

AAnalyze

Analyze Phase

17


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.

IImprove

Improve Phase

18


Control Phase CControl

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


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.

Cp 2.0 and Cpk 1.67

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