1. Lean Six Sigma – Project
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Lean Six Sigma Black Belt Project
Version 4.0
2. Lean Six Sigma – Project
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Name of the Project : Reduction Main frame failure in
Fabrication category within warranty hours
(Model- ZX-140 )
Name of Black Belt : 1. Mukesh Choudhary
2. Rajat S Panday.
3. Viresh Haromachadi
4. Karan Kumar Chhawchharia
Organization : Tata Hitachi construction Machinery PVT LTD, Dharwad.
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Main frame failure location
CFU ( Center frame Unit) Joint crack
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Machine application photographs
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Project Charter
Authors : Rajat S
Panday/ Mukesh
Choudhary
Project Name: Reduction in Main frame failure
within warranty hours (Model- ZX140)
Date:
06/06/2021
Business Case Customer satisfaction was less due to 8.55% of main frame failure which
is impacting more warranty cost
Project Objectives Reduction in main frame failure from 8.55% to 0.1 % in 2years
Main matric Reduce:- Defect ratio of Main frame failure from 8.55% to 0.1% (Main)
Sub matric Warranty cost from 41.8 L to 0.00 from last FY’20-21.
Expected Savings INR41.8Lac per annum (from FY’20-21)
Project Scope No Main frame failure up to 5000 HMR or 2 year.
Project Schedule Team Members and other Recourses
Project Identification 25/05/2021 Champion Mr. Ranganath Kamath
Define 07/06/2021 MBB Dr. Prabhu.
Measure 05/07/2021 BB Mukesh, Amit, Viresh, Karan
Analyze 28/08/2021 Supplier end support Mr. Sridhar , Mr. Rajendra D ( QC)
Improve / Design 20/10/2021 Field data support Mr. Pratap reddy (CQA)
Control / Verify 20/11/2021 Testing data support Mr. Jyoti Barik (QA Testing)
Close 25/12/2021 Design support Mr. Anil ( Design).
Signature Champion_________________
Signature BB/ GB___________________
Manufacturing
process support
RSB (Supplier team)
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Author: Mukesh Choudhary Project Name: Reduction in Main
frame failure within warranty
hours (Model-ZX140)
Date:06/05/2021
Problem Statement
Main frame failure in warranty hours leading to high
warranty cost & less customer satisfaction
Current level of Performance (In
terms of productivity, cycle time,
cost)
Main frame failure in ZX140 model is 8.55 %
Expected level of Performance (In
terms of productivity, cycle time,
cost)
Main frame failure reduced by 0.1% from 8.55%
Savings of cost / time / efforts/
manpower per transaction or unit
Rs. 94210 /unit
Total Monetary savings INR 41.8 lac per annum
Assumptions (in terms of person
day cost, manpower cost, defect
rework cost, call resolution costs,
etc.)
Project Charter- Saving Estimation
Note: Period of data FY-20-21
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Matrix Diagram to Prioritize Pain / Gain Areas
Alternate Issues / Problems Savings Cust. Sat. Business Grand rating
Reduction in Main frame failure in
warranty hours (Model- ZX140)
4 5 5 100
Reduction in Boom failure in
EX130
3 4 5 60
Defect reduction in
Commissioning issue (0-100HMR)
2 5 5 50
UT straight pass improvement at
supplier end
2 5 5 50
Project Identification and Prioritization
Problem selected : Reduction in ZX-140 Main Frame failure from 8.55% to 0.1%.
9. Lean Six Sigma – Project
Yearly Main frame Failure in terms of PPM
Slide Owner: Nitesh Updated on : 22-01-2019 Freq:
Monthly
52,154.0
135,231.0
85,585.0
0
25,000
50,000
75,000
100,000
125,000
150,000
2018-19 2019-20 2020-21
PPM
Value
Failure is getting every year. 2019-20 maximum Machine has matured
so failure PPM is more and one action was taken in 2019-20, after that
failure has reduced but still failure is contributing.
Our target to achieve 1000 PPM from 85585PPM
CM-1 was taken.
10. Lean Six Sigma – Project
PPM Fraction Z-score
85321 0.085 1.372
1000 0.001 3.09
% improvement in PPM 44.40
Distribution Plot
As per probability distribution plot
44.4% improvement seen, hence
selected this failure for improvement.
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Warranty failure in terms of Cost (Apr’20-Mar’21)
Already action taken for this
2 components failure.
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Project Identification and Prioritization
Action taken in
Oct’20.
And it is effective
79% Failure cost is contributing Main frame
failure
Hence finally selected Main frame failure in our project .
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Data Collection Plan
Sl No What to measure / record
Type of
measure
How / Where to measure
Sample method
/ frequency
Who will
measure
Where to
record
1 Area Attribute CFU Welding area
2 Nos per shift
based on job
availability
Welder/
inspector
Check sheet
2 Shift Attribute A / B
3 Operator NA Ramesh kumar
4 Model NA ZX140
5 Punch No- Attribute Identification Number
6 Type of Joint Attribute Joint type as per SOP
7 Gas Flow (LPM) Variable
Manufacturing process (RSB)
8 Wire size (mm) Variable Manufacturing process (RSB)
9 Weld position Attribute Manipulator Axis setting
10 Current (A) Variable
Manufacturing process (RSB)
11 Voltage (V) Variable
12 Stickout length (mm) Attribute
13 Ok/Not ok Attribute Visual welding inspection QC inspector
14 Defect Type Attribute Field
Field service
engg.
15 Field failure Data variable No of failures Customer QA Report
16 Stress Variable On the failure location Proto job Testing QA Report
15. Lean Six Sigma – Project
Process flow diagram- Main frame Assembly.
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| Tata Hitachi Construction Machinery Company Pvt. Ltd. | 2015
FAILURE STATUS ( From Apr’18- Mar’21 )- Field data
Location No of machines
Madurai 36
Cochin 31
Chennai 27
Salem 7
Aurangabad 4
Hyderabad 3
Nagpur 3
Udaipur 3
Guwahati 3
Delhi 2
Nellore 2
Chandigarh 2
Indore 2
Pune 2
Ahmedabad 2
Bhubaneshwar 2
Hubli 2
Jabalpur 2
Lucknow 1
Jaipur 1
Raipur 1
Kolkata 1
Total 139
HMR Range Quantity
2001-3000 43
3001-4000 39
1001-1500 20
4001-5000 17
1501-2000 15
501-1000 5
As per data, Machine Location & number
of failed machines both are attribute data
so applied Chi-square test
Rock breaker 66
Rock breaker and Bucket 73
Application No of Mcs
Blue metal Quarry 81
MINING : Marble 19
MINING : Granite 17
Mining Lime-stone 3
Others 19
Grand Total 139
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H0- number of failures are equal in each location.
Ha- number of failures are not equal in each location.
Hence the P value is less than 0.05 , so the null is rejected
As per Chi-square test ,number of failure is different at different loca
Chi Square test field failure location wise
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Chi Square test for field failure HMR band wise
H0- number of failure in
each HMR Band is equal
Ha- number of failures in
each HMR Band is not
equal
Hence the P value is less
than 0.05 , so the null is
rejected
As per Chi-square test ,
number of failure is
increasing in higher HMR
band.
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Main frame failure location
C/M – Inside Triangular plate added to reduce the stress in Main
frame and F/M done before MSN- 470.
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Failures after 1st CM:
HMR Range No of Machines
1-500 221
501-1000 188
1001-1500 192
1501-2000 155
2001-2500 146
2501-3000 73
3001-4000 82
4001-5000 44
5000+ 29
Total 1130
HMR Range
No of failures
after CM *
1001-1500 1
1501-2000 1
2001-3000 2
3001-4000 5
4001-5000 4
>5000 3
Total 16
All the failures are in
Blue Metal quarry
application
Machine population after CM:
Application No of Mcs
Construction 537
Bluemetal Quarry 228
MINING : OTHERS 108
MINING : SAND 62
AGRICULTURE :
OTHERS 52
INFRASTRUCTURE 47
Others 40
MINING : GRANITE 26
MINING : LIMESTONE
(CEMENT) 19
MINING : MARBLE 11
Grand Total 1130
Note: All failure modes considered after CM (cutoff MSN 470 –Year- 2019)
Application wise Machine
population after CM:
Failure details after CM:
21
*374 Mcs. crossed 2000
hours.
29 Machines has crossed
27. Lean Six Sigma – Project
Unskilled operator
Bucket
Rock Breaker
Attachment Material
Main frame
crack from Collar
Joint.
Measurement
Travel %
Swing %
Rock
Application
Morrum
FISH BONE DIAGRAM- Categorize all brain storming points
Blue metal
Salt digging
Agriculture
Input
material
Machine
Idling ratio
Man
Sand
Sand loading
Bricks
Dozer
Rock
breaker
Sand
Bucket
HD Bucket
GP Bucket
SOP not followed
Stage inspection
Lack of Knowledge
Welding position
Machine calibration
Supervision
Voltage setting
Current adjustment
Gas flow
Human error
Material
preparation
Material
preparation
Wrong programming
Wire feed
Material chm prop
Material
grade
Material
thk.
FEA
Stress test
Weld
penetration
Testing
Welding size
R & R Testing
chm prop of welding
wire
Welding wire
Bucket size
Welding
machine
28. Lean Six Sigma – Project
Welded Joints
KPOV
KPIV
KPIV / KPOV (For Main frame Failure joint )
• Good Penetration
• Good fusion with side wall and root
• No Welding defects in the joint
• Less distortion
• Good weld appearance
• Good Welding strength
• Dimensional accuracy of cut plates
• High skill operator
• No fluctuation in current , voltage and gas flow parameters
• No contamination in weld area (dust , oil , rust , moisture etc.)
• No deviation in weld sequence / Correct teaching
• Robo machine programming.
• Correct weaving
• Groove size to be maintained as per SOP/drawing.
• Plate fit up gap to be maintain as per HGS (max 1.6mm)
Low hanging Fruit:
1.Contamination can be control immediately
2.Groove size can be maintained as per SOP/Drw
29. Lean Six Sigma – Project
Tata Hitachi Dharwad
Potential Failure Mode and Effects Analysis (Process FMEA)
Part Name- Main frame Part No- 50006674XXXTB Prepared by : CFT
Team members- Mukesh, Amit, Karan, Viresh Date- 11th June'21
Process Function
Potential
failure
mode
Failure
effects SEV Potential causes Prevention control Occ.
Recom
mende
d
action Detection Det RPN
Recomm
ended
action
SE
V
O
CC
De
t
RP
N
Mig welding
Uniform
weld
deposition
uneven
weld
deposition
( Weld
size)
Chances of
failure of
Main frame
from CFU
welding joint
area incase
welding is
non uniform.
Impact to
Customer
7
Variation in welding parameter (Voltage,
Current, Gas flow rate)
Process parameter
verificatibon to be
done on test piece.
2
1. 100 % Weld
bead inspection
2. 100% Visual
Inspection
5 70
Wrong selection of welding wire
Welding wire details
is inccluded in SOP /
WI
2
Only one size
Welding wire is
being used
4 56
Un Skilled operator
Qualified welder
appointed at station
3
100% welder
supervison
4 84
Non adherence of Preventive
maintenance of welding M/C
Adherance to
preventive
maintenance plan of
welding M/C
3
Stage wise
inspection
inplace
4 84
Variation in input material condition
(beveling land, Beveling angle)
Weld
Penetration -
70% Min. of
min. plat
thickness
Less weld
penetratio
n
Chances of
failure of
Main frame
from CFU
joint incase
welding
penetration
will be less
Impact to
customer
8
Variation in welding parameter (Voltage,
Current, Gas flow rate, Torch Speed)
Process parameter
verificatibon to be
done during first
piece approval
3
Welding
automatio
n by
Robotic
welding
Process
parameter
monitoring in
stage
inspection
5 120
Frequency
reduced
to check
the weld
penetratio
n in
Sample by
making T
joint (Test
piece)
Frequency
- Weekly
8 2 2 32
Wrong selection of welding wire
Welding wire details
is inccluded in SOP /
WI
3
Only one size
Welding wire is
being used
4 96
Un Skilled operator
Qualified welder
appointed at station
3
100% welder
supervison
4 96
Non adherence of Preventive
maintenance of welding M/C
Adherance to
preventive
maintenance plan of
welding M/C
2
Stage wise
inspection
inplace
4
64
Variation in input material condition
(beveling land, Beveling angle)
Welding
defects
(B/H,
Porosity,
Non
fusssion,
undercuts)
1.Chances of
failure of
Main frame
from CFU
joint incase
define
welding
defects.
2. Poor
asthetic
6
Variation in welding parameter (Voltage,
Current, Gas flow rate, Torch Speed)
Welding process
parameter defined in
SOP.
2
100% visual
inspection
3 36
Environmental condition
Welding done in close
area
3
100% visual
inspection
3 54
Failure mode and effect analysis
30. Lean Six Sigma – Project
As per welding process failure effect analysis there are no
possibility of welding failure.
Verify the Weld parameter found weld penetration as per
spec, and process parameter followed as per SOP.
Hence decided to verify the application testing.
1. FEA testing
2. Stress testing
FMEA Summary
31. Lean Six Sigma – Project
S.NO 4 M CONDITION PARAMETER OBSERVATION REMARKS
1
Man
Welder skill All welders are certified OK
2 Operator changed No new operator put on job. Welders are skilled (Level 5) OK
3
Material
Material of welding wire Chemical properties of wire found within specification OK
4 Material of Steel Plates
Chemical properties and hardness of plate– checked with MTC
and Spectro analysis done at THCM lab and found OK
OK
5 Welding distortion No Welding distortion found after completion of welding OK
6 Child part
Lug, vertical plates , top plate, all verified for dimensional
inspection & found ok as per drawing
OK
7
Method
Plate cutting Plate cutting verified , no visual defects observed OK
8 Welding parameters
As welding done in continuous curved area torch angle
consistency will be the concern point
Improvement
point
9 Welding at joints/Toe Welding joint checked & no defects observed OK
10 Joint assembly Assembly fit up gap is less than 1mm in all the areas OK
11 Welding SOPs Welding SOP is available OK
12
Machine
Condition of welding machine Condition of welding machine found OK OK
Welding manipulator Welding positioner available (This joint is done in 2F position ) OK
13
14 Gas flow meter Gas flow rate (20/25 LPM) and meter found OK OK
4M analysis based on Process audit (for Mode 3, 4 & 6)
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Below 4M conditions verified in 04 nos. visits to RSB DWR done and verified with 05 part samples
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Verification of Analysis
Counter Measure : Robotic welding to be started in curved area
instead of Manual welding to reduce the target line variation.
Why
Main frame crack from welding Joint from Lug plate curvature
welding Joint.
Why Variation in weld fusion.
Why There were no consistency in welding target line
Why Weld Torch angle variation was getting
Why Welding was done in curve area
Why Welding done manually. Root
Cause
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Contradiction:
Torch angle may shift in Manual welding process, which may impact weld
penetration & size
Solution:
Consistency in welding size & welding penetration
TRIZ solution:
Automation Robot welding to be introduce for consistency in welding size
& welding penetration
Existing process:
Mechanical substitute
Main frame welding failure
TRIZ: 40 Principle
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Contradiction:
Change in weld parameter will impact the weld penetration & fusion
Solution:
Consistency in welding size , welding penetration & fusion
TRIZ solution:
Fixed the welding parameter in automation
Existing process:
Parameter change
Main frame welding failure
TRIZ: 40 Principle
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Defect Mode Defect details Activity Done
Action Proposed for
Improvement
Where Status
Mode-3 & 6.
MSN-
783/816.
HMR:3097,1
970
Mode 4
MSN-
728/816.
HMR:1429,1
970
Crack from Lug
plate curvature
welding joint
(Cabin side & Tool
Box both side ).
Crack from Lug
plate boom foot
main welding
(Cabin side)
1. Welding process parameter was as per
spec.
2. It was observed that as welding to be
done in curved area so torch angle
consistency in manual welding will be a
concern point – Improvement point.
1. This joint is
suggested for ROBO
welding.
2. Robo welding trials
done, validated by
cut section analysis
and implemented.
3. Kamata san (HCM
Expat ) suggested of
straight profile for
40mm plate as like
in ZX140 BS4
machine
RSB
Done
.
MSN
-
1436
Action plan
36. Lean Six Sigma – Project
Improvement Action 2 – ZX140 - Main frame failures
Before
After
Inside and outside reinforcement added to reduce the stress
37. Lean Six Sigma – Project
Robo trial observation for Defect Mode 3, 4 & 6
Robo trial findings:
1). Sample piece made for Robo Trial-
Observations of the Trial-
a). Weld size of lug to bend plate (spec- 10mm; actual- 12*11mm)- OK
b). Weld size of lug to vertical plate (spec- 7mm; actual- 6mm)-NOT OK
2nd Trial- found OK (7*8mm)
2). Cut section analysis has been done & found OK.
3). Spectro analysis of plate material carried out at THCM lab.
4). All 03 plates meeting specifications of material and are found OK.
Note:- Discussion done with HCM expert and
concluded the action plan for defect mode-3, 4 & 6.
38. Lean Six Sigma – Project
Failure Mode 3, 4 & 6– Process audit observations
Process Audit Observation :
1. Job is verified at tack welding stage, & found ok as per drawing &
standards- OK
2. Welding process of failure joint is been verified with THCM PE &
QC , No deviation noted in the process- OK
3. After welding fillet size is checked, 7*7 mm fillet observed 8*9 mm –
OK
4. It was observed that as welding to be done in curved area so torch
angle consistency will be a concern point – Improvement point
Improvement Points;
1. For further improvement , this joint is suggested for ROBO welding.- Done
2. Welding SOPs revised & approved by THCM PE.
3. Kamata san suggested of straight profile for 40mm plate as like in ZX140 BS4 machine. Sep’21
1St Run
2nd Run
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39. Lean Six Sigma – Project
Robo trial findings:
1). Sample piece made for Robo Trial- (1st trial done on 06.08.2021 )
Observations of the Trial-
a). Weld size of lug to bend plate (spec- 10mm; actual- 12*11mm)- OK
b). Weld size of lug to vertical plate (spec- 7mm; actual- 6mm)-NOT OK
2nd Trial- found OK (7*8mm)
2). Cut section analysis has been done & found OK
ROBO Trials
Sample Piece 1st Robo Trial 2nd Robo Trial
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40. Lean Six Sigma – Project
ROBO trial sample piece & cut section analysis
Sample Piece
1 2 3 4 5 6
40
Cut section analysis done after Robo welding found ok
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Plate Material verification- Spectro analysis
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1
2
3
1
Plate part Material
specs
Check
results
Plate 1-40mm E250 BR OK
Plate 2-20mm E250 BR OK
Plate 3-14mm E250 BR OK
• Spectro analysis of plate material carried out at THCM lab.
• All 03 plates meeting specifications of material and are found OK.
Hence Robo welding implementation result is satisfactory
Now decided to Move for Mode-1 & Mode-2
42. Lean Six Sigma – Project
S.NO 4 M CONDITION PARAMETER OBSERVATION REMARKS
1
Man
Welder skill All welders are certified OK
2 Operator changed No new operator put on job. Welders are skilled (Level 5) OK
3
Material
Material of welding wire Chemical properties of wire found within specification OK
4 Material of Steel Plates
Chemical properties and hardness of plate– checked with MTC
and Spectro analysis done at THCM lab and found OK
OK
5 Welding distortion No Welding distortion observed after welding OK
6 Child part Stiffener plate is verified as per drawing & found ok OK
7
Method
Plate cutting No defects observed on the plate cutting OK
8 Welding parameters Welding parameters , torch angle ,position found ok OK
9 Welding at joints/Toe Welding joint is checked & no visual defects observed OK
10 Joint assembly No Assembly gap between vertical plate to stiffener plate. OK
11 Welding SOPs Welding SOP available and followed OK
12
Machine
Condition of welding machine Condition of welding machine found OK OK
Welding manipulator Welding manipulator available at supplier OK
13
14 Gas flow meter Gas flow rate (20/25 mm) and meter found OK OK
4M analysis based on Process audit (for mode 1 & 2)
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Below 4M conditions verified in 04 nos. visits to RSB DWR done and verified with 05 part samples
43. Lean Six Sigma – Project
Failure Mode 1 & 2 – Process audit observations
Audit Observation :
1. Job is verified at Child part & tack welding stage, & found
ok as per drawing & standards- OK
2. Welding process of failure joint is been verified with THCM
PE & QC , No deviation noted in the process- OK
3. 40mm extension found 44/46mm , & smooth grinding found
OK–OK
4. 10mm fillet weld is observed 12*12mm – OK
Conclusion-
1. Decided to verify the Stress at failure location
Mode 2 Mode 1
2mm
gap
UT started
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OPTION 1 - OUTSIDE PATCH PLATE ( After 1st time failure study )
ORIGINAL DESIGN , CABIN SIDE
OPTION 1-OUTSIDE PATCH PLATE
PATCH PLATE
NOTE: This exercise was carried out in Proto-2 machine inside plant.
| Tata Hitachi Construction Machinery Company Pvt. Ltd. | 2015
45. Lean Six Sigma – Project
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| Tata Hitachi Construction Machinery Company Pvt. Ltd. | 2015
59.7
OPTION 1 – OUTSIDE PATCH PLATE ( FEA RESULT )
45.4
ORIGINA
L
** All values are in MPa
OPTION
1
FEA Result-
A Reduction of 24 % (from 59.7 to 45.5) in the failure area was observed.
46. Lean Six Sigma – Project
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| Tata Hitachi Construction Machinery Company Pvt. Ltd. | 2015
OPTION 1 , (STRESS TEST RESULT, INHOUSE)
| Tata Hitachi Construction Machinery Company Pvt. Ltd. | 2019
OPTION 1
LONGITUDINAL
MAX MIN P-P
CRITERIA 300 -300 400
M51 202 -224 426
ORIGINAL DESIGN
LONGITUDINAL
MAX MIN P-P
CRITERIA 300 -300 400
M196 198 -233 431
RESULT: There are no difference in Stress value, only 1.2% improvement
HENCE OPTION 1 IDEA WAS DROPPED
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| Tata Hitachi Construction Machinery Company Pvt. Ltd. | 2015
OPTION 2 - INSIDE PATCH PLATE ( On the basis of stress result)
CABIN SIDE- INSIDE PATCH PLATE
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| Tata Hitachi Construction Machinery Company Pvt. Ltd. | 2015
ORIGINAL
** All values are in MPa
OPTION 2
25.2
OPTION 2 - INSIDE PATCH PLATE ( FEA RESULT )
59.7
FEA Result-
A Reduction of 57 % (from 59.7 to 25.2) in the failure area was observed.
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| Tata Hitachi Construction Machinery Company Pvt. Ltd. | 2015
OPTION 2 ( STRESS TEST RESULT AT SITE-MADURAI, WITH ROCK BREAKER )
A B C
Max. 300 14 98 112
Min. -300 -8 -119 -151
P-P 400 21 218 263
ROCK BREAKER W X Y Z
Max 300 123 104 70 124
Min -300 -49 -45 -34 -64
P-P 400 172 149 104 188
ROCK BREAKER
ORIGINAL DESIGN M/C SL NO. 436 OPTION 2 M/C SL NO. 489
RESULT: 31% ( from 218 to 149) Reduction in stress found in failure area with
R/B in Blue metal application after addition of Inside Reinforcement plate.
GAGE LOCATION IN ORIGINAL DESIGN
GAGE LOCATION IN OPTION 2
• FAILURE STARTING
POINT IS B
• POINT X IS
EQUIVALENT
TO POINT B
36 OUT OF 103 FAILURES WERE OBSERVED IN MADURAI ,SO STRAIN
GAGING WAS DONE AT MADURAI LOCATION
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| Tata Hitachi Construction Machinery Company Pvt. Ltd. | 2015
0
50
100
150
200
250
300
350
400
450
ORIGINAL INSIDE PATCH PLATE
STRESS AT FAILURE LOCATION WITH INSIDE
PATCH
149 MPa
CRITERIA = 400MPa
218 MPa
RESULT: 31% ( from 218 to 149) Reduction in stress found in failure area with
R/B in Blue metal application after addition of Inside Reinforcement plate.
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| Tata Hitachi Construction Machinery Company Pvt. Ltd. | 2015
OPTION 3 – PROFILE PLATE ADDITION
CABIN SIDE- ORIGINAL
CABIN SIDE- PROFILE PLATE
PROFILE PLATE
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| Tata Hitachi Construction Machinery Company Pvt. Ltd. | 2015
OPTION 3 – FEAANALYSIS
OPTION 3
** All values are in MPa
ORIGINAL
59.7 53.7
FEA Result-
A Reduction of 10 % (from 59.7 to 53.7) in the failure area was observed.
53. Lean Six Sigma – Project
A B C
Max. 300 16 77 78
Min. -300 -60 -137 -133
P-P 400 76 213 211
ROCK BREAKER
53
| Tata Hitachi Construction Machinery Company Pvt. Ltd. | 2015
OPTION 3 ( STRESS TEST RESULT WITH ROCK BREAKER )
A B C
Max. 300 14 98 112
Min. -300 -8 -119 -151
P-P 400 21 218 263
ROCK BREAKER
ORIGINAL DESIGN M/C SL NO. 436
GAGE LOCATION IN ORIGINAL DESIGN GAGE LOCATION IN OPTION 3
ORIGINAL DESIGN M/C SL NO. 436
RESULT: No significant difference in stress observed.
Hence rejected the proposal 3.
54. Lean Six Sigma – Project
To reduce the Main frame failure through DOE TOOLS
Response Variable :-
• Weld Size
Scope & Size of the experiments :-
• 3 factors at 2 levels identified to study
and optimize the parameters.
• 2 Replications on Randomized Pattern
• Others Parameters kept constant.
Objective :-
To maintain weld parameters
Levels
Current – 280-320A
Voltage- 28-32V
Gas flow- 20-25
Factors :- 3
1. Current
2. Voltage
3. Gas flow .
Experimental Plan
Full Factorial
( Considering each Main Effect & each Interaction )
Number of experiment – 8.
DF= 8+1=9
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By analysing the data using Minitab.
P value for all experiment found more than 0.05.
Factors- current , Voltage , Gas flow & their interactions P value is >0.05 ,
Hence Factors are not significant.
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Effect plot is as below. Current, voltage, gas flow & their
interaction is not a vital cause
As per pareto chart
no factors are
significant.
Hence decided to
reduce the stress
value.
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Verification of Analysis
Counter Measure : Covered all point in stress testing with 4.6m Boom, 2.1m
Arm and 0.73cu GP Bucket and decided to reduce the Stress.
Why
Main frame crack from Boom mounting Lug vertical plate and
stiffener plate extension. .
Why Maximum failure is getting in Hard application.
Why More stress getting.
Why
During stress testing all Point was not covered as per hard
application.
Root
Cause
58
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59
Contradiction:
Stress result not achieved as per requirement
Solution:
Stress value to be reduced
TRIZ solution:
Reinforcement plate to be added to reduce the stress .
Existing process:
Partial and excessive action
Main frame failure due to High stress.
TRIZ: 40 Principle
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Contradiction:
Vibration is getting more in Hard application, which is impacting Main
frame failure
Solution:
Support require to reduce the vibration
TRIZ solution:
Reinforcement plate to be added to reduce vibration so that less impact
of stress will be less.
Existing process:
Mechanical vibration
Main frame failure due to more vibration
TRIZ: 40 Principle
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Defect
Mode
Defect details Activity Done Direct cause Action Proposed for Improvement Where Status
Mode-1.
MSN-593
HMR -
2564
Crack from
Boom mounting
lug vertical
plate (Cabin
side)
1. Child component and welding
process parameter verified
found ok
2. Stress verified found more
stress
Stress failure
Reinforcement plate added inside and
outside the main frame to reduce the
stress level.
RSB Done
Mode-2.
MSN- 470
HMR- 3484
Crack from
Stiffener plate
extension
welding crack (
Cabin side)
1. Welding process of failure
joint verified, No deviation
noted in the process- OK
2. Stress verified found more
stress
Stress failure
Reinforcement plate added inside and
outside the main frame to reduce the
stress level
RSB
Done
Action plan
Conclusion:-
1. Welding parameters are not impacting.
2. Stress is getting more
Hence plan to verify the impact of welding process by applying DOE tools
62. Lean Six Sigma – Project
Improvement Action 3 – ZX140 - Main frame failures
Before
After
Inside and outside reinforcement added to reduce the stress
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ZX140 current model – 40mm plate
curved profile
ZX140 BS4 model – 40mm plate
straight profile
Improvement Action 4 – ZX140 - Main frame failures
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ZX140 BS4 mainframe observations
64
• Cabin side out side stiffener plate
added in ZX140 BS4 frame.
• Also 40mm plate profile changed.
• Now it is with straight profile
65. Lean Six Sigma – Project
Improvement Action – ZX140 - Main frame failures
Before
After
Outside and Inside reinforcement plate added to reduce the
stress and part taken for testing
Only Inside Reinforcement plate added
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Stress Result –Verification.
NG found in
some location.
Bigger size
Bucket was
used
１,Purpose and Overview
The purpose of this test was to check the stress level in the Mainframe CFU section
with the addition of Outside Patch Plate.
Considering the previous NG's in ZX140 machine the gauge pasting is also done in
Boom Cylinder lug, & tailframe area including CFU section.
２，Test date and tester
Models ：ZX 140
Unit ：TDD140-001
Test day ：11/9/2021
Measurer : Kiran, Prashant
Machine Operator : : Balaraj
Testing location ：Dharwad
Machine configuration
: 4.6m Boom,
2.1m Arm,
0.73 GP
Bucket.
３，The results
Total NO. of
gages
: 226
Total NO. of
gages
: 02 (MF 103, MF 151)
Damaged
Total NO. of gages : 5
above specification
Judgement
NG
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Stress Result –Verification.
ZX 140 Mainframe stress test data with Outside patch plate
Basic
Concentrated
Gauge
Positions
Longitudinal Operations Transverse Operations D & C 1st
Time Rough Road
Criteria
(10%
Less)
-270 270 360 -270 270 450 -270 270 405 -360 360 540
MIN MAX
P-P
MIN MAX
P-P
MIN MAX
P-P
MIN MAX
P-P
MF 2
-237 223 460 -69 80 149 -137 130 267 -136 114 250
BOOM
UP
BOOM
UP
MF 90
-196 204 399 -87 70 157 -140 146 286 -125 78 203
J UP
MAX
CENTER
PULL
MAX
CENTER
MF 214
-175 123 298 -288 241 529 -108 51 158 -129 63 191
SWING
HIT
ARM V
LHS
SWING
HIT
MAX
RHS
MF 221
-282 221 503 -120 113 232 -143 150 292 -192 151 343
BOOM
UP
BOOM
UP
MF 222
-312 297 609 -302 132 434 -151 309 460 -213 182 395
BOOM
UP
BOOM
UP
SWING
HIT
ARM V
LHS
D&C 0˚
1 TIME
D&C
90˚ 1
TIME
Stress found
at some area.
so decided
restress
testing.
Restress
testing is in
progress.
PDC-W1-
Oct’21
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Project Summary status
SL NO Activity Status
01 Selection of six sigma project Completed
02 Team formation Completed
03 Project chatter Completed
04 Project identification prioritization by Metrics diagram Completed
05 Data collection. Completed
06 Gemba visit and Brain storming Completed
07 Statistical approach (apply Chi square) to understand the defect Completed
08 Scatter and Weibull plot to understand the defect severity. Completed
09 Applied DOE tools to analyze the exiting process Completed
10 Stress test done to understand the improvement Completed
11 Applied TRIZ principle to decide the improvement action Completed
12 Improvement action taken ( Mode-2 , 3 & 6) Completed
13 Improvement action taken ( Mode- 1 & 2) Sample received Completed
14 Re stress testing for Mode 1&2 ( Awaiting stress test result) On going
15 Control To be done
