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Scope of six sigma in indian foundry operations
1. Scope of Six Sigma in Indian foundry
operations: a case study
By
Dr. Bikram Jit Singh
Professor
MMDU Mullana
2. CEO/CHAMPION: RA/BJS DATE: 20-01-2011
Project Name: Reduction in scrap of Bajaj classic 5-Port pistons.
1 BUSINESS CASE
Rejection in foundry defect are taking place at two stages,
a) Rejection at foundry stage
b) Rejection detected at final inspection after machining, value addition takes
place during the manufacturing operations, project of improving piston rejection
of BCL5-P has been selected in Piston Foundry
For a particular machined number of blanks due to higher rejection good out put
is reduced , which in certain cases results in plan /customer requirements not
being met in Time.
With Low rejection hence more good out put good result in lower product cost
the actual benefits of 6 lakhs per annum is to be achieved.
The saving are calculated on the basis of benefits observed in manufacturing cost
due to scrap reduction at current level of production.
3. Rejection in foundry are taking place at two stages,
a) Rejection at foundry stage
b) Rejection detected at final inspection after machining, value addition takes
place during the manufacturing operations, project of improving material
rejection in CSA24 applications has been selected in Piston Foundry
For a particular machined number of blanks due to higher rejection good out
put is reduced , which in certain cases results in plan /customer requirements
not being met in time.
With Low rejection hence more good out put good result in lower product
cost the actual benefits of 6 Lakhs per annum is to be achieved.
The saving are calculated on the basis of benefits observed in manufacturing
cost due to scrap reduction at current level of production.
4.
5. 0
10
20
30
40
50
60
Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec
Baja Classic5P (Avg. 29.08%)
Baja Classic 5P
(Avg.29.08%)
7. Financial Parameters (in Rs) Bajaj Classic 5-port
Scrap /Month 4582
Scrap cost/ Piston 153
Total rejection cost / Month 7,01,046
Total rejection cost / Year 84,12,552
8. Premelt-
ing R & R
Pre
Melting
Chips
Age
Hardening
Burr
Cutting
&
Fettling
Metal
Treatment
Casting
Composition
check through
spectrometer
Visual and
Dimensional
Checking
Visual &
Hardness
checking
Approval of
Brick mould
test & Density
Index
Alloying
Blank
Store
In Goting
Inspection
Storage
Operations
10. Production results of July-2011
Total number of Machined parts 15797
Scrap type Nos.
Shrinkage in Skirt (S3) 1976
Shrinkage on Top (S1) 812
Porosity on Skirt (P3) 519
Porosity on Top (P1) 406
Shrinkage in Ring Zone (S2) 348
Blow holes in Ring Zone (B1) 290
Blow holes on Skirt (B3) 231
Total Scrap in june 4582
Nos. of Oppertunities 7
DPMO 41436
Sigma level of process 3.2
Yield 69%
12. Date Feb 1 3 4 5 6 7 8 10 11 12 13 14 15 18 19 20 21 22 24 25
Time
X1
X2
X3
X4
N/s
M/s
A/s N/s
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
X1 0.4 0.3 0.4 0.6 0.3 0.4 0.4 0.4 0.5 0.4 0.3 0.3 0.4 0.3 0.4 0.1 0.6 0.4 0.4 0.3
X2 1.2 0.2 0.3 0.4 0.4 0 0.5 0.3 0.3 0.3 0.4 1.2 0 0.4 0.3 0.2 0.4 0.5 0.4 0.4
X3 0.5 0.3 0.4 0.4 0.4 0.2 0.3 0.5 0.4 0.3 0.5 0.2 0.4 0.3 0.5 0.2 0.4 0.4 0.3 0.3
X4 0.2 0.4 0.3 0.4 0.4 0.4 0.4 0.4 0.4 0.6 0.5 2.3 0.5 0.4 0.5 0 0.5 0.4 0.4 0.3
Xbar 0.5750 0.3000 0.3500 0.4500 0.3750 0.2500 0.4000 0.4000 0.4000 0.4000 0.4250 1.0000 0.3250 0.3500 0.4250 0.1250 0.4750 0.4250 0.3750 0.3250
Range 1.000 0.200 0.100 0.200 0.100 0.400 0.200 0.200 0.200 0.300 0.200 2.100 0.500 0.100 0.200 0.200 0.200 0.100 0.100 0.100
Sub Group Size= 4 A2= 0.729 D3= 0 D4= 2.28 D2=
Standard deviation (s) R =
Gauge stability= s X100 %
BIAS CONTROL CHART METHOD BIAS
ULX = d2=
Xdbar = = =
LCLx = d2*=
UCLr = tv,1-a/2 = Lower Limit =
R bar =
LCL = 0 alpha = 0.05 Upper Limit =
Result Gage is not well stable
0.036220294
0.163
0.4075
2.05875
0.3350
0.76
2.06813
2.000
0.479612034
0.40750
0.16198208
28.26765674
0.6517
2.059
0.197873597
0.335388
R
e
a
d
I
n
g
s
Tolerance
*2d
R
r =s
g
r
b
s
s =
13. Analyse
METAL
OPERATORMETHOD
DIE
Temperature
Metal Treatment
1) Gas
2) Nucleation
Composition
Air venting
Flow lines
Cooling cycle
Pre-heating of
die
Good tool paint
Good die paint
Pouring
Filter insertion
Filter size
APPLICATION –BC 5P
Outer mould
relief
Rear side tool paint
Hourly out putPin stick air cooling
Die cleaning
Water
Circulation
SHRINKAGE
POROSITY &
BLOW
HOLES
ON SKIRT &
Top (CROWN)
CAUSE AND EFFECT DIAGRAM
Outer Dia
18. Response Surface Regression: Casting Scra versus Metal Temper, Cooling Time, ..
The analysis was done using coded units.
Estimated Regression Coefficients for Casting Scrap
Term Coef SE Coef T P
Constant 11.0000 0.7707 14.272 0.000
Metal Temperature -0.1429 0.5641 - 0.253 0.810
Cooling Time -2.3929 0.5641 -4.242 0.008
Degassing Time -0.3750 0.4720 -0.795 0.463
Metal Temperature*Metal Temperature 5.6012 0.8972 6.243 0.002
Cooling Time*Cooling Time -3.6488 0.8972 -4.067 0.010
Degassing Time*Degassing Time 7.3988 1.0731 6.895 0.001
Metal Temperature*Cooling Time 0.2262 1.3852 0.163 0.877
Metal Temperature*Degassing Time 1.5000 0.6675 2.247 0.075
Cooling Time*Degassing Time 1.7500 0.6675 2.622 0.047
S = 1.33497 PRESS = *
R-Sq = 98.03% R-Sq(pred) = *% R-Sq(adj) = 94.48%
27. Cur
High
Low0.99997
D
Optimal
d = 0.99997
Targ: 10.0
Casting
y = 10.0005
0.99997
Desirability
Composite
450.0
650.0
100.0
180.0
720.0
780.0
Cooling DegassinMetal Te
[750.9091] [151.7172] [552.9324]
29. Production results of July-2011
Total number of Machined parts 17252
Scrap type Nos.
Shrinkage in Skirt (S3) 1976
Shrinkage on Top (S1) 812
Porosity on Skirt (P3) 519
Porosity on Top (P1) 406
Shrinkage in Ring Zone (S2) 348
Blow holes in Ring Zone (B1) 290
Blow holes on Skirt (B3) 231
Total Scrap in june 2416
Nos. of Oppertunities 7
DPMO 20006
Sigma level of process 3.6
Yield 85%
30. Financial Parameters (in Rs) Bajaj Classic 5-port
Scrap /Month 2416
Scrap cost/ Piston 153
Total rejection cost / Month 3,69,648
Total rejection cost / Year 44,35,776
Net saving in scrap per month 3,31,398
Net saving in scrap per annum 39,76,776
32. Deptt.: PISTON FDY. Line 3,Cell2
Piston Type: Bajaj Classic 5 Port AC9A ALLOY
Parameter Specification Observation Remarks
Scrapping of crucible walls Clean walls ok was done before tapping of metal in HF
Drossing off with Cov11
MEASURING SPOON
(300gms+50 gms )
WITH MEASURING SPOON YES 329 gms
Holding Furnace Clean from Slag visual clean Not Clean Not ok
Degassing - - Ar 553±10 secs 555 OK
Waiting time 5 MIN MINIMUM 3 Min 50 sec Not ok
Sample probe Visual SAMPLE PISTON TURNED Gas free, ok
Density Index upto 1.0 0.6 Ok
Casting temp. 750±10ºC HF 3 Line 2-759ºC OK
Die cooling cycle 150±10 secs 148 OK
Luff Sticks/air vents Open open
Luff stick not present in left
tool
left tool opened and sent for providing luff stick
Tool wear out No wear NO WEAR OK
Casting Spoon Refer specification Coated ok
Die Paint/ Padding Hatching Lines not Visible NOT OK CASTER called and advised to refill the padding
Core grouping Proper steps No Tool Shifting ok