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Scope of six sigma in indian foundry operations

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Keywords: critical to quality variables; automotive mission plan; AMP; process mapping; cost of poor quality; response surface methodology; RSM; contour plot; process audit sheet; p-chart; sigma calculator; measurement system analysis; MSA; India; six sigma; foundry operations; make-to-order foundries; die casting foundries; optimisation.

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Scope of six sigma in indian foundry operations

  1. 1. Scope of Six Sigma in Indian foundry operations: a case study By Dr. Bikram Jit Singh Professor MMDU Mullana
  2. 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. 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. 4. 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%)
  5. 5. Pareto Analysis Material Scrap of BCL 5 PORT 43.04% 17.72% 11.39% 8.86% 7.59% 6.33% 5.06% 100.00% 81.01% 88.61% 94.94% 72.15% 60.76% 43.04% 0.00% 5.00% 10.00% 15.00% 20.00% 25.00% 30.00% 35.00% 40.00% 45.00% 50.00% ShrinkageonSkirt S3 ShrinkageonTop S1 PorosityonSkirt P3 ShrinkageonTop B1 Shrinkageinring zoneS2 blowholeinring zoneB2 BlowHoleonSkirt B3 Parameters %age 0.00% 10.00% 20.00% 30.00% 40.00% 50.00% 60.00% 70.00% 80.00% 90.00% 100.00% Commulative%age
  6. 6. 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
  7. 7. 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
  8. 8. Casting
  9. 9. 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%
  10. 10. msa STABILITY TEST PART NAME : GAUGE NAME &L.C: Vac Tester TOLERANCE : MM MASTER VALUE: mm X=Averrage X UCL= X+A2R= LCL=X - A2R= R = average R UCL=D4xR LCL=D3xR 0 0.4075 0.3350 0.7645 CSA-18 alloy 0.70 0.16330.6517 0.00 0.0000 0.1000 0.2000 0.3000 0.4000 0.5000 0.6000 0.7000 0.8000 0.9000 1.0000 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 0.0000 0.5000 1.0000 1.5000 2.0000 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Oneunit=Oneunit= ucl Lcl ucl Lcl
  11. 11. 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 =
  12. 12. 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
  13. 13. 790 Degree770 Degree750 Degree730 degree 100 90 80 70 60 50 40 30 20 10 Data Boxplot of 730 degree, 750 Degree, 770 Degree, 790 Degree 790 Degree770 Degree750 Degree730 degree 100 90 80 70 60 50 40 30 20 10 Data Individual Value Plot of 730 degree, 750 Degree, 770 Degree, 790 Degree
  14. 14. 116 Secs90 Secs 60 50 40 30 20 10 Data Boxplot of 90 Secs, 116 Secs 116 Secs90 Secs 60 50 40 30 20 10 Data Individual Value Plot of 90 Secs, 116 Secs
  15. 15. 700500300 50 40 30 20 10 CL2AR 50 40 30 20 10 Type of Gas Degassing Time AR CL2 of Gas Type 300 500 700 Time Degassing Interaction Plot for Casting Scrap Data Means
  16. 16. Metal Temperature Cooling Time Degassing Time Casting Scrap 750 140 550 10 780 140 450 22 750 100 650 14 750 140 550 11 750 140 550 12 720 140 450 25 750 180 450 12 780 180 550 10 780 140 650 26 750 100 450 20 720 140 650 23 780 180 550 11 720 100 550 16 750 180 650 13 720 180 450 18
  17. 17. 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%
  18. 18. 28262422201816141210 1.0 0.5 0.0 -0.5 -1.0 Casting Scrap Residual Residuals Versus Casting Scrap (response is Casting Scrap)
  19. 19. 5 10 15 100 125 150 100 125 150 15 20 175 600 540 480 660 600 Casting Scrap Degassing T ime Cooling T ime Metal Temperature 750 Hold Values Surface Plot of Casting Scrap vs Degassing Time, Cooling Time
  20. 20. Cooling Time DegassingTime 180170160150140130120110100 650 600 550 500 450 Metal Temperature 750 Hold Values > – – – – – < 5.0 5.0 7.5 7.5 10.0 10.0 12.5 12.5 15.0 15.0 17.5 17.5 Scrap Casting Contour Plot of Casting Scrap vs Degassing Time, Cooling Time
  21. 21. 10 15 20 720720 740 760 720 740740 25 480 780 600 540 480 660 600 Casting Scrap Degassing T ime Metal T emperature Cooling Time 140 Hold Values Surface Plot of Casting Scrap vs Degassing Time, Metal Temperature
  22. 22. Metal Temperature DegassingTime 776768760752744736728720 650 600 550 500 450 Cooling Time 140 Hold Values > – – – – < 12 12 15 15 18 18 21 21 24 24 Scrap Casting Contour Plot of Casting Scrap vs Degassing Time, Metal Temperature
  23. 23. 5 10 720 740 760 720 740740 15 780780 150 125 100 175 150 Casting Scrap Cooling T ime Metal T emperature Degassing Time 550 Hold Values Surface Plot of Casting Scrap vs Cooling Time, Metal Temperature
  24. 24. Metal Temperature CoolingTime 776768760752744736728720 180 170 160 150 140 130 120 110 100 Degassing Time 550 Hold Values > – – – – < 5.0 5.0 7.5 7.5 10.0 10.0 12.5 12.5 15.0 15.0 Scrap Casting Contour Plot of Casting Scrap vs Cooling Time, Metal Temperature
  25. 25. Cooling Time DegassingTime 180170160150140130120110100 650 600 550 500 450 Metal Temperature 750 Hold Values 10 29 Scrap Casting Contour Plot of Casting Scrap
  26. 26. 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]
  27. 27. Response Optimization Parameters Goal Lower Target Upper Weight Import Casting Scra Target 5 10 29 1 1 Global Solution Metal Temper = 750.909 Cooling Time = 151.717 Degassing Ti = 552.932 Predicted Responses Casting Scra = 10.0005 , desirability = 0.999973 Composite Desirability = 0.999973
  28. 28. 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%
  29. 29. 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
  30. 30. 31st July 28th July 25th July 22nd July 19th July 16th July 13th July 10th July 7th July 4th July 1st July 0.225 0.200 0.175 0.150 0.125 0.100 0.075 0.050 Time IndividualValue _ X=0.1406 UCL=0.2178 LCL=0.0635 p chart for scrap monitoring
  31. 31. 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

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