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Six Sigma BB Project
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Project Number : 01
Project Description
Bore Diameter 35 mm Unclean
in Throttle Body AC-35.
Six Sigma BB Project
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DOE Project Description
Name of BB - Mr. Arvind Gupta (ACMA-ACT)
Team members - Mr. N.Prakash, Mr.I.P. Batra (UCALFuel Systems Limited,Gurgaon)
Annual Cost Of Poor Quality: Rs, 1,78,610/-
Project reference: 001/04 -05
Date of Start : 20/07/04
Phases Compl.
Date
Phase-1 20-07-04
Phase-2 22-07-04
Phase-3 03-08-04Phase-4 10-08-04
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DOE Project
Cost of Poor Quality Breakup
Rework Cost : NIL
Machining Cost : Rs 56,448/-
Raw Material Cost : Rs.1,22,162/-
Intangible Savings1. Internal Customer Satisfaction.
2. Smooth flow of products.3. Learning of Systematic Approach to solve the problem.
4. Breakthrough in the company towards the attitude.
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Phase 1- Definition
Problem definition - Bore Unclean-(reduced from 0.56 % to ZERO.)
Response definition - Attribute
Instrument to be used - Visual
R&R study details -Not Required
Potential SSVs from
FMEAs\ Brain storming Brain storming
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Phase-1- Definition
Problem & Response Definition
Problem Statement- Bore diameter 35 mm unclean in Throttle Body AC-35.
Response to be measured- Bore Unclean ( Attribute)
Specification-No Unclean
Instrument used to verify the Response- Visual
Least Count of the instrument-Not Applicable
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Phase 1 Definition
R&R study details
Is R&R study required for the Measurement
system -No
Result of R&R study
% E.V. -Not Applicable
% A.V. -Not Applicable
% R & R -Not Applicable
Ph 1 D fi i i
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Phase 1 Definition
Listing Potential Source of Variation
Y = f (X)Where Y= Response ( Unclean in Bore)
X = Suspected Source of Variation (SSV)
SSVs are:1. Mounting Hole Dia. 6.5 +0.2/+0
2. Mounting Hole Position w.r.t. Bore (X axis) 24 +/- 0.05
3. Mounting Hole Position w.r.t. Bore (Y axis) 28+/- 0.05
4. Mounting Face Flatness 0.05 Max
5. Step in Bore Diameter35 at Casting Stage .
Ph 1 D fi iti
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Phase 1 Definition
Drawing/Photograph
Throttle Body
35 Bore
Unclean
Mounting Face
0.05 max.
Locating HolesDia 6.5+0.2/0.0
24 +/- 0.05
28 +/-0.05
Ph 1 D fi iti
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Phase 1 Definition
Drawing/Photograph
Throttle Valve
Throttle Body
Sensor Bracket
Ph 1 D fi iti
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Phase 1 Definition
Drawing/Photograph
Locating Pins Clamp
Boring BarFixture
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Phase 2 Measure and Analyze
Shainin DOE Tool selection - Paired Comparison
Data collection - Yes
Analysis of Data - Yes
Conclusion based on data - Yes
Ph 2 M d A l
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Phase2 Measure and Analyze
Tool selection
Initial Tool selected
Since the SSVs- Mounting Holes Diameter 6.5 mm
, Hole Positions w.r.t Bore center ( x & y co-ordinates) 24 & 28 mm and Mounting Face Flatness
can be checked on Good & Bad Parts both , D.O.E.
Tool selected was Paired Comparison.
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Phase 2 Measure and Analyze
Data Collection
Good andBadparts selected based on the Response( Bore
unclean)
8 Best of Best (Good) and8 Worst of Worst (Bad)parts
selected based on the Response.
SSVs Dimension 28+/- 0.05 , 24 +/-0.05 , Hole Size 6.5 +0.2/-0 &
Flatness of mounting face 0.05 max. measured on both Good and
Badparts and analyzed for the counts.
Phase 2 Measure and Analyze
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S.N. Dimn 28+/-0.05 Result S.N. Dimn 28
+/-0.05 Result
1 27.95 G 1 27.93 B
2 27.95 G 2 27.94 B3 27.96 G 3 27.96 G
4 27.96 G 4 27.97 G
5 27.96 G 5 27.98 B
6 27.96 B 6 27.99 B
7 27.97 G 7 28.00 B
8 27.97 B 8 28.00 B
9 27.97 B 9 28.01 B
10 27.97 G 10 28.03 G
11 28.03 B 11 28.04 G
12 28.03 B 12 28.05 B
13 28.04 B 13 28.05 G
14 28.05 B 14 28.06 G
15 28.06 B 15 28.06 G
16 28.06 G 16 28.06 G
COUNT = ZERO COUNT = 5.5
Phase 2 Measure and Analyze
Data Collection and analysis
Hole -
1
Hole -
2
Not A
Cause
Not A
Cause
Phase 2 Measure and Analyze
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S.N. Dimn 24+/-0.05 Result S.N. Dimn 24+/-0.05 Result
1 23.94 B 1 23.97 B2 23.95 B 2 23.97 B
3 23.95 B 3 23.98 B
4 23.95 G 4 23.99 B
5 23.95 B 5 24.00 B
6 23.95 B 6 24.01 B
7 23.96 B 7 24.03 B
8 23.96 B 8 24.05 B
9 23.97 G 9 24.05 G
10 23.97 G 10 24.05 G
11 23.97 G 11 24.05 G
12 23.98 B 12 24.05 G
13 23.99 G 13 24.05 G
14 24.00 G 14 24.06 G
15 24.00 G 15 24.07 G
16 24.03 G 16 24.07 G
COUNT = 5 COUNT = 10
Hole -1
Hole -2
Phase 2 Measure and Analyze
Data Collection and analysis
Not A
Cause
One of
the
Cause
Phase 2 Measure and Analyze
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S.N.Hole Dia 6.5
+0.2/-
0.0Result S.N.
Hole Dia 6.5+0.2/-
0.0Result
1 6.61 B 1 6.62 B
2 6.62 B 2 6.62 B
3 6.63 B 3 6.62 B
4 6.63 B 4 6.63 B
5 6.63 B 5 6.63 B
6 6.64 B 6 6.63 B7 6.64 B 7 6.65 B
8 6.64 B 8 6.66 B
9 6.66 G 9 6.66 G
10 6.66 G 10 6.66 G
11 6.66 G 11 6.66 G
12 6.66 G 12 6.67 G
13 6.66 G 13 6.67 G
14 6.66 G 14 6.67 G
15 6.67 G 15 6.67 G
16 6.67 G 16 6.67 G
COUNT = 16 COUNT = 12
DATA COLLECTION FOR SSV'S
Phase 2 Measure and Analyze
Data Collection and analysis
Hole -
1
Hole -
2
RootCause Root
Cause
Phase 2 Measure and Analyze
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S.N.
Flatness of
Mounting Face
0.05 Max.
Result
1 0.020 G
2 0.020 G
3 0.025 B
4 0.025 G
5 0.025 G
6 0.026 G
7 0.028 B
8 0.028 G
9 0.030 B
10 0.035 G
11 0.035 B
12 0.038 B
13 0.040 B
14 0.042 B
15 0.045 B
16 0.050 G
COUNT = ZERO
Phase 2 Measure and AnalyzeData Collection and analysis
Not A
Cause
Phase 2 Measure and Analyze
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S.N.
Hole Dia 6.5+0.2/-
0.0 Result
1 6.61 B
2 6.62 B
3 6.63 B
4 6.63 B
5 6.63 B6 6.64 B
7 6.64 B
8 6.64 B
9 6.66 G
10 6.66 G
11 6.66 G
12 6.66 G
13 6.66 G
14 6.66 G
15 6.67 G
16 6.67 G
Analysis:
Phase 2 Measure and AnalyzeData Collection and analysis
Since the count is=16, Mounting
Hole size Dia 6 mm
is one of the
strongest
cause of theproblem
Phase 2 Measure and Analyze
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S.N.Hole Dia 6.5
+0.2/-
0.0Result
1 6.61 B
2 6.62 B
3 6.63 B
4 6.63 B
5 6.63 B
6 6.64 B7 6.64 B
8 6.64 B
9 6.66 G
10 6.66 G
11 6.66 G
12 6.66 G
13 6.66 G
14 6.66 G
15 6.67 G
16 6.67 G
COUNT = 16
Conclusions:
Phase 2 Measure and AnalyzeData Collection and analysis
Inference from the dataGOOD ---6.66 ~ 6.67 mm
BAD------6.61 ~ 6.64 mmDrg. Spec. 6.50~6.70mm
Variation in the Process
6.61 ~ 6.67 = 0.06 mm(within Spec.)
Locating Pin size---6.57mmClearance between Pin and
locating hole
GOOD
Max.6.67-6.57=0.1mm
Min.6.66-6.57=0.09mmBAD
Max.6.64-6.57=0.07mm
Min 6.61-6.57= 0.04mm
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Phase 3 Improvement
Conclusions ( Root Cause):
From the analysis ,it is evident that clearance between
Locating Pin & Mounting hole varying from 0.09 to 0.1result in GOOD Product wherein clearance rangingbetween 0.04 to 0.07 mm result in BAD product.
So we need to maintain the clearance between Pin &
Hole min 0.09 mm.
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Phase 3 Improvement
Opportunities available
Option No.1:To Change the Spec of Hole Size from present 6.5+0.2 to6.66+0.06mm ( To maintain min clearance 0.09) which requires drillsize change & also sought approval from customer as the drawing is
customer approved. Subsequent fitment at the customer end wasalso a constraint, so Option no.1 was ruled out.
Option no.2 : To modified the Pin size from present 6.57 to 6.52 to
maintain minimum clearance of 0.09 mm ( As per data for GOOD
parts).Option -2 ,Implemented.
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Phase 3 Improvement
After the countermeasure taken, 100 %inspection of the parts carried out visually on
the machine for bore unclean problem.
Rejection found to be
ZERO out of total 15,000parts made till now.
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Phase 4 - Control
Tool drawing Has been modified & standardizedfor the locating pin size 6.57 to 6.52 mm.
FMEA has been updated.
Control Plan( maintenance) has been revised forthe pin change frequency.
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Phase 4 - Control
MATERIAL :EN 31
HARDNESS :40~50HRC
QUANTITY :1 NOS
ALL SHARP
CORNERS TO BE
CHAMFERED
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Bore Unclean
Paired Comparison
DOE TOOL
DOE TOOL
0
10
2030
40
50
60
70
80
90
1 st Q tr 2 nd Qt r 3r d Qt r 4 th Q tr
East
West
North
FUNNELING BY 6 SIGMA
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Phase 4 - Control
Variation analysis:
Since the variation in the hole size is less than 50 % of the
tolerance,Pre-control chart has been implemented on themachine to record the variation in the hole size due to drill worn
out at hole drilling stage.
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Phase 4 - Control
Scatter plot has been introduced on the machine to
record theno .of parts produced and the variation in
hole size to find out (optimize) Tool ( drill ) Life.
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Horizontal Deployment
Throttle Body AC-38
Phase 4 - Control
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Phase 4 - Control
Although problem now seems to be easy ,but it was
difficult in the beginning to find out the root cause of the
problem as generally it is perceived that more clearancebetween hole & pin will cause the problem whereas in
this case , it was a case of less clearance causing the
problem.
Learning:
To avoid the twist of the part while mounting on to thefixture ,Min clearance between the locating pin & hole
shall be kept 0.1 mmapprox( Subject to fitment and function of
the part).
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Project Completed
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