Fracture analysis and defect reduction in passenger car rim
1. FAILURE ANALYSIS & DEFECT REDUCTION IN
PASSENGER CAR RIM
Team Members (BATCH-16)
1. Swaminathan.S 171001109
2. Tharun Kumar.C 171001111
3. Vignesh.S 171001116
Project type : Industry
Internal Supervisor : Dr.S.ARUMUGAM
Designation : Assistant professor
Organisation : SVCE
External Supervisor Name: Mr.V.SATHISH KUMAR B.E.,MBA.,
Designation : Senior Manager
Organisation : Wheels India Ltd.
2. S.No ACTIVITY
MONTH 1 MONTH 2 MONTH 3
FEB W3 FEB W4 MAR W1 MAR W 2 MAR W3 MAR W4 APR W1 APR W2 APR W3 APR W4
1 AIM AND OBJECTIVE
2 BASIC STUDY ABOUT M/C
3 DEFECT STUDY
4 CURRENT TREND ANALYSIS
5
TEMPERATURE BEHAVEOUR FOR
VARIOUS PARAMETER
6 MATERIAL STUDY
7 QUALITY PARTS VERIFICATION
8 IDENTIFYING THE CAUSE
9 DEVELOP SOLUTION USING DOE TOOLS
10
MONITORING RESULTS AND
COMPARING WITH PREVIOUS RESULTS
11 FINAL REPORT PREPARATION
LEGEND PLAN COMPLETED NOT COMPLETED
PROJECT PLAN
3. Wheels India Ltd.
Wheels India Limited is company promoted by the TVS Group, India’s
largest auto component manufacturers. Wheels India started
production of wheels for commercial vehicles in 1962 at our plant in
Padi, Chennai.
Products
Wheels
Air Suspension
Energy equipment parts
Heavy engineering
Fab division
Customers
Hyundai
Nissan
Toyota
Ford
Maruti Suzuki
Isuzu
PSA Citroen
7. Resistance Welding
• Resistance welding is the joining of metals by
applying pressure and passing current for a length
of time through the metal area which is to be
joined.
• The electrodes, typically manufactured from
copper based alloys due to superior conductive
properties, are cooled by water flowing through
cavities inside the electrode and the other
conductive tooling of the resistance welding
machine.
8. Flash (Butt) Welding
• Flash (butt) welding is an electrical resistance
welding processes used for joining components,
where the energy transfer is provided primarily by
the resistance heat from the parts themselves.
The components are positioned end-to-end across
the full joint area.
9. (a) (c)
(b) (d)
Electrodes
Position and Clamp the Parts
Apply Flashing Voltage
and Start Platen Motion
Flash
Upset and Terminate Current
The basic steps in a flash welding
sequence are as follows:
10. Flash Welding
Pros Cons
Flexible cross sectioned shapes
Produce unbalance on three-phase primary
power lines
Flexible positioning for similar cross section
parts
The ejected molten metal particles present a
fire hazard
Impurities can be removed during upset acts Require special equipment for removal of
flash metal
Faying surface preparation is not critical
except for large parts
Difficult alignment for workpieces with small
cross sections
Can weld rings of various cross sections Require almost identical cross section parts
Narrower heat-affected zones than those of
upset welds
14. Butt Welding Platen movement
11mm
BED GAP = 23mm
RETRACTION =2mm
FLASH = 6mm
UPSET =8mm
1
2
3
15. Machine and Rim Specification
S.no Main Parameters Data
1 Main circuit rated input voltage AC380V/1phase
2 Control circuit rated input voltage AC380V/3phase/50Hz
3 Secondary voltage 8.8V to 14.6V
4 Flash Current 450 Amps
5 Upset Current 1300 Amps
6 Upsetting pressure 45 bar (or) 652.67 psi
7 Clamping Pressure 65 bar (or) 942.74 psi(fixed)
8 Max welding cross section area 4000mm^2
9 Width of rim 200 mm
10 Thickness of rim 2.3 mm
11 dia of rim welded 350 mm
12 Cooling water flow rate 5000L/H
13 Pressure of cooling water 0.2-0.4MPa
14 Temp. of cooling water 28°C- 30°C
15 Rejection rate <= 0.5%
16. 3.Possible Defects
Failures caused during:
Butt welding Heeling Over Lap Butt weld fuse
Butt weld air leak Deep flash cut Flash cutting: Shallow Crack at coining
Crack at forming Crack at expanding Uneven flash cut
23. FUSE - DEFECT SELECTED FOR REDUCTION
Macro examination of weld taken near failure
Macro examination of weld taken away from failure
UNEVEN FUSION
OR UNBURN
MATERIAL IS
CALLED AS FUSE
DEFECT
26. 6.Material Study and Analysis
S.No
Mechanical properties Thermal Properties Composition
Ultimate
Tensile
MPa
Young’s
modulus
GPa
Brinnel
Hardnes
s
Yield
Strength
MPa
Latent
heat of
fusion
J/g
Meltin
g onset
˚C
Thermal
expansi
on
µm/mk
Density
g/cm^3
Carbon
%
Mangan
ese
%
1 440 190 130 270 250 1360 13 7.3 0.2 0.75
2 590 190 180 370 250 1420 13 7.8 0.09 1.69
27. Material Composition
Element C Si Mn P Al V Nb
%Wt 0.09 0.13 1.69 0.013 0.031 0.007 0.02
**NOTE:
Mn/Si < 25% (recommended)
Reason:
Increase in Mn/Si ratio increases the
brittleness of the material.
29. ULTIMATE STRENGTH ANALYSIS
TENSILE STRENGTH AND BENDING TEST
S.No SAMPLE UTS(MPa) Elang.(%)
BENDING
(TON)
BENDING
RESULT
1 OK PART 596.3 22 43 PASS
2 OK PART 602.5 28 42 PASS
3 OPEN CRACK 236.4 9.4 19.5 FAIL
4 OPEN CRACK 220.4 8.6 16.2 FAIL
5 FUSED 173.9 3.9 6.2 FAIL
6 FUSED 178.2 4.5 8 FAIL
30. 7.Q-PARTS VERIFICATION
S.No Points to be checked Checking method Frequency
1 Block bolt tightness Tight Daily
2 Grip bolt tightness Tight Daily
3 Ensuring lubrication in platen
arm connecting pin
Proper lubrication flow Daily
4 Hydraulic oil filtration Checking its color Daily
5 Spatter card No spatter accumulation
in ring to prevent short-
circuit
Daily
6 Tightness of electrical
connection ( Brider ) in
control panel
Check as per PM schedule Weekly
31. S.No Points to be checked Checking method Frequency
7
Clamp pressure for any
pressure drop
Maintain set value Daily
8
Upset pressure for any
pressure drop
Maintain set value Daily
9 Upset current Maintain set value Daily
10
Working of air cooler system
for heat control card in
welding control panel
Check temperature below
30 degree
Daily
32. 8.CAUSE AND EFFECT DIAGRAM
(Fish-Bone diagram)
Operator Skill
SOP & WI
adherence
Improper tool
setting
Upset pressure
High
low
Resistance in platen movement
Clamping pressure
Load variation in clamping
Poor conductivity
Current variation during flashing
Short circuit in machine
Bed gap variation
High panel temperature
Gap between block & block holder
Bed to bed height variation
Flaring % high in coning
Deep flash cutting
Rim got cold while flash cutting Excess edge cutting
Material out of squareness
Tool condition
Tool damage
Tool wear
Block to block height variation
Edge burr in slitting edge
Rusted material
Block and grip cumulative height variation
High
Low
Butt welding
Fusing issue
No. of suspected causes : 26
Bed to bed parallelism
Projection of packing
33. S.No CAUSES ACTION OBSERVATION RESULT
1 Operator skill
Operator skill level in skill
matrix
Welding is performed by trained
professionals
Ok
2 Improper tool setting
The set parameters must be of
the recommended values
The parameters are cross checked
twice with their spec within a shift
Ok
3 SOP & WI adherence Awareness of SOP & WI
The operators are interviewed about
SOP& WI and evaluated
Ok
4 Deep flash cutting
The thickness of the base
material to be checked after
flash cutting
It is checked using a thinning gauge
and measured ±0.1mm from base
thickness
Ok
5 Flaring % high in coning
Flaring % to be less than 10%
in coning
Wheel code wise flaring % is
checked and found to be les than
10%
Ok
6 Edge burr in slitting edge
The edges should be free of
burr
The strip is free of burr after
shearing the edges
Ok
7 Tool condition
The tool working condition
and contact surface must be
free of damage
The tool is checked and its in
working condition with no damage
to be found
Ok
34. S.No CAUSES ACTION OBSERVATION RESULT
8
Block to block height
variation
The block in the moving and
fixed plates should be of equal
height
Every block is checked of its height
in the tool room before setting fixing
it in the machine
Ok
9 Material out of squareness
The error in the squareness of
the material should be less
than 1mm
Squareness error checked during
slitting and found around 0.5mm
Ok
10 Rusted material
Material should be free of rust
in the welding edges and
clamping area
The material is checked and found to
be rust free
Ok
11
Block and grip cumulative
height variation
The block and grip height
placed together should be
between 102 to110mm
Their cumulative is measured in the
tool room and taped together as a
set
Ok
12 Upset pressure variation
Measure Upset pressure in
pressure gauge and pressure
accumulator gas pressure
The upset pressure remained close
to the spec and accumulator gas
pressure is 20 bar
Ok
13
Resistance in platen
movement
The smooth movement of
platen is required
The platen is moved manually and
the disturbance was checked using a
stethoscope
Ok
14 Clamp pressure variation
Measure clamp pressure in
pressure gauge and pressure
accumulator gas pressure
The clamp pressure remained close
to the spec and accumulator gas
pressure is 25 bar
Ok
35. S.No CAUSES ACTION OBSERVATION RESULT
15 Improper loading of band
Complete butting of band to
back stopper should be
ensured
The band butted properly in the
back stopper and no healing
occurred
Ok
16
Short circuit in machine
bed
There should be no current
flow in between weld beds
during open welding
The current flow is checked using an
ammeter
Ok
17 Poor conductivity No heat variation
The heat varied from time to time
during welding
Not ok
18 Bed to bed height variation
Bed to bed height variation
should be less than 0.5mm
It is checked using parallel block and
feeler gauge and 0.2mm variation
observed
Ok
19 Bed to bed parallelism
Bed to bed parallelism error
should be less than 1mm
It is checked using parallel block and
dial gauge and 0.7mm variation
observed
Ok
20
Gap between block and
block holder
This leads to poor conductivity
Gap found and improper block
seating found
Not ok
21
Heat control guard
temperature
Increase in temperature cause
malfunction of the device
leading to improper
temperature control
Interlock available for temperature
control
Ok
36. S.No CAUSES ACTION OBSERVATION RESULT
22 Bed gap variation
DOE TOOL TAKEN
FOR FURTHER
VALIDATION
23 Excess edge cutting
24 Projection of packing
25
Flash cutting after rim got
cold
26
Peak current in second
flash start
37.
38. 9.DOE TOOLS TAKEN FOR VALIDATING
THE PRODUCT DIMENSIONS
PRODUCT
SuspectedSources of
Variations (SSV’s)for the
physical phenomenonof
the problem
PC PPS CS MCS MVA CC VS FF OBS B VS C
Bed gap variation
Peak currentin second flash start
Projection of electrodepacking
Flash cutting after rimgotcold
Excess edgecutting
Machine
Method
PC – Paired Comparison, PPS – Product/Process search, CS – Component search MCS –
Modified Component search MVA – Multivari analysis VS – Variable search, FF – Full
factorial, OBS – Observation, CC – Concentration chart
39. DOE TOOL : PRODUCT/PROCESS
SEARCH TOOL
OBJECTIVE:
To Validate Machine & method related
Possible Causes.
Technique/Tool used:
Product/ Process Search Tool
RECORD THE SSV AND PROCESS COLLECT
8 GOOD AND 8 WORST SAMPLES
AND ARRANGE THE DATA IN
ASCENDING ORDER
WHERE COUNT SHOULD BE >= 6 FOR A
SIGNIFICANT FACTOR
40. DOE TOOL : PPS-Machine
Home Position Variation
(Set 23mm)
G 22.9
G 22.9
G 23
G 23.1
G 23.1
B 23.2
G 23.3
B 23.4
B 23.4
B 23.4
B 23.5
G 23.6
G 23.6
B 23.7
B 23.8
B 23.8
Count = 8
INITIAL BED GAP
/ PLATEN HOME
POSITION
Cause
No
What to
Verify ?
How Actual Observation Result
22
Bed gap
variation
PPS
(spec
±0.5mm
max)
Count = 8; Count
greater than 6 is a
contributing factor
NOT
OK
SIGNIFICANT
41. DOE TOOL : PPS-Method
EXCESS EDGE CUTTING
(mm)
B 8
G 8
G 8
G 10
B 10
G 11
G 11
B 11
G 13
G 13
B 13
B 14
G 15
B 15
B 15
B 15
Count = 3
Cause
No
What to
Verify ?
How Actual Observation Result
23
Excess edge
cutting
PPS
Count = 3; Count
greater than 6 is a not a
contributing factor
OK
Edge cutting
NOT
SIGNIFICANT
42. DOE TOOL : PPS-Machine
SHIM PROJECTING OUT
(mm)
B 3
G 3
G 3
G 4
G 4
G 4
B 4
B 4
G 5
B 5
B 5
G 5
B 6
B 6
G 7
B 7
Count = 1
Cause
No
What to
Verify ?
How Actual Observation Result
24
Projection of
electrode
packing
PPS
Count = 1; Count
greater than 6 is a not
contributing factor
OK
LOOSE PACKING
NOT
SIGNIFICANT
43. DOE TOOL : PPS-Method
RIM GOT COLD WHILE
FLASH CUTTING
(sec)
G 1
B 1
G 2
B 2
G 3
G 3
B 4
B 4
B 4
G 4
B 4
G 4
G 4
B 4
B 5
G 5
Count = 1
Cause
No
What to
Verify ?
How Actual Observation Result
25
Flash cutting
after rim got
cold
PPS
Count = 1; Count
greater than 6 is a not
contributing factor
OK
Rim should be in red
hot condition during
flash cutting
NOT
SIGNIFICANT
44. DOE TOOL : PPS-Machine
PEAK CURRENT IN
SECOND FLASH STARTING
G 250
G 250
G 250
G 275
G 280
G 300
B 500
B 500
G 500
B 600
B 600
B 650
B 650
G 700
B 700
B 720
Count = 7.5
Cause
No
What to
Verify ?
How Actual Observation Result
26
Current
variation
during flashing
PPS
(Variation in
current
during flash
change
over)
Count = 7.5; Count
greater than 6 is a
contributing factor
NOT
OK
Flash current
variation
SIGNIFICANT
45. DOE SUMMARY REPORT
Home Position
Variation
(Set 23mm)
G 22.9
G 22.9
G 23
G 23.1
G 23.1
B 23.2
G 23.3
B 23.4
B 23.4
B 23.4
B 23.5
G 23.6
G 23.6
B 23.7
B 23.8
B 23.8
Count = 8
SIGNIFICANT
EXCESS EDGE
CUTTING
(mm)
B 8
G 8
G 8
G 10
B 10
G 11
G 11
B 11
G 13
G 13
B 13
B 14
G 15
B 15
B 15
B 15
Count = 3
NOT SIGNIFICANT
SHIM PROJECTING
OUT
(mm)
B 3
G 3
G 3
G 4
G 4
G 4
B 4
B 4
G 5
B 5
B 5
G 5
B 6
B 6
G 7
B 7
Count = 1
NOT SIGNIFICANT
RIM GOT COLD
WHILE FLASH
CUTTING (sec)
G 1
B 1
G 2
B 2
G 3
G 3
B 4
B 4
B 4
G 4
B 4
G 4
G 4
B 4
B 5
G 5
Count = 1
NOT SIGNIFICANT
PEAK CURRENT IN
SECOND FLASH
STARTING
G 250
G 250
G 250
G 275
G 280
G 300
B 500
B 500
G 500
B 600
B 600
B 650
B 650
G 700
B 700
B 720
Count = 7.5
SIGNIFICANT
46. Why Why Analysis
Root Cause No: 17
Poor electrical
conductivity
Number of contacts
in current passage is
high
To achieve required
cumulative height
Bottom electrodes
are made of number
of layers
Block Assembly design
Counter measure: Block
assembly design to be
modified
47. Why Why Analysis
Root Cause No: 20
Gap between block
and block holder
Improper block
seating
Block has projected
packing
To achieve required
cumulative height
Block Assembly design
Counter measure: Block
assembly design to be
modified
48. Why Why Analysis
Root Cause No: 22
Initial bed gap
variation
Platen over travel
while return stroke
No control over
platen movement in
reverse stroke
Return stroke speed
is high and inertia
effect
Only one DC valve is engaged in return stroke
Counter measure: REVERSE
Flow control valve to be
engaged for reverse stroke
49. DOE TOOL : VARIABLE SEARCH TOOL
ROOT CAUSE NO: 26 (Current variation during flashing)
A
• 1st flash flow control in points
B
• 2nd flash flow control in points
C
• Heat control in %
Current
variation
50. DOE TOOL: VARIABLE SEARCH TOOL
No PARAMETER ( - Setting ) ( + Setting )
A 1st flash flow control 2.3 2
B
2nd flash flow control 1.2 1.5
C Heat control in % 85 78
Based on the experience, Parameters will be changed
FIRST LEVEL OPTIMAL SETTINGS
51. Test - Setting + Setting
1st Run 750 400
2nd Run 700 450
3rd Run 600 380
Median 700 400
Range 150 70
D ( Difference Between Two
Medians )
300
d = Average of Two Ranges 110
D/d 2.7
AS THE D/d RATIO IS > 1.25 , IT SHOWS THAT +SETTING
PARAMETER ARE EFFECTING THE RESPONSE IN POSITIVE DIRECTION
DOE TOOL: VARIABLE SEARCH TOOL
52. PEAK CURRENT IN SECOND
FLASH STARTING
G 250
G 250
G 250
G 275
G 280
G 300
B 500
B 500
G 500
B 600
B 600
B 650
B 650
G 700
B 700
B 720
Count = 7.5
Test - Setting + Setting
1st Run 750 400
2nd Run 700 450
3rd Run 600 380
Based on the Validation by PPS tool we
are getting GOOD samples when the
Current is below 300A.
So to Optimize the parameter 2nd level
Optimal setting parameter derived and
Revalidated with Variable search tool.
53. DOE TOOL: VARIABLE SEARCH TOOL
No PARAMETER ( - Setting ) ( + Setting )
A 1st flash flow control 2 1.8
B
2nd flash flow control 1.5 1.7
C Heat control in % 78 70
Based on the experience, Parameters will be changed
SECOND LEVEL OPTIMAL SETTINGS
54. Test - Setting + Setting
1st Run 450 200
2nd Run 380 250
3rd Run 450 200
Median 450 200
Range 70 50
D ( Difference Between Two
Medians )
250
d = Average of Two Ranges 60
D/d 4.16
AS THE D/d RATIO IS > 1.25 , IT SHOWS THAT +SETTING
PARAMETER ARE EFFECTING THE CURRENT VARIATION
DOE TOOL: VARIABLE SEARCH TOOL
55. No PARAMETER
BEFORE
( - setting)
AFTER
( + Setting )
A 1st flash flow control 2.3 1.8
B 2nd flash flow control 1.2 1.7
C
Heat control in % 85 70
SOLUTION FOR 26 : Parameter optimization to
avoid Flash current variation
56. SOLUTION FOR 17 & 20: Single piece block
replaced multi layered block assembly
BEFORE AFTER
Used Multi layered block
used with Top and Bottom
packing
(Up to 7 layers)
Single piece block used with
Top and Bottom packing to
reduce the conductivity
loss.(Maximum 3 layers used)
58. SOLUTION FOR 22 : Flow control valve engaged in reverse
stroke to avoid bed gap home position variation
BEFORE
There is no flow control valve
to control the flow for the
home position (Reverse
stroke). Due to inertia force
bed position getting varied.
59. SOLUTION FOR 22 : Flow control valve engaged in reverse
stroke to avoid bed gap home position variation
AFTER
Flow control valve
introduced in reverse
stroke to control the
return speed while return
stroke.
61. RESULT COMPARISON
PROPERTY BEFORE AFTER
DIFFERENCE
IN %
LP1401
SCRAP (PPM)
6263 947 84.87
PROPERTY BEFORE AFTER
DIFFERENCE
IN %
FUSE SCRAP
(PPM)
4626 204 95.59
95.59%
62. PROPERTY BEFORE AFTER DIFFERENCE IN %
SCRAP (PPM) 10059 4745 52.83
RESULT COMPARISON
The ring weld is illustrated in the above slide. Because the distance across the flash welded surface is shorter than the distance around the hoop, current tends to flow across the interface making the flash weld. However, a sizable amount of shunt current follows the path around the hoop, thus higher currents are generally required when shunt paths like this are present. Often, the preheat cycle is eliminated as this would tend to preheat the entire part and additional heat at the interface would raise the resistance there and force more shut current into effect.
Three common types of welds made by flash welding are shown in this and the following two slides.
The axially aligned weld is shown in the above slide.
