DEFECT ANALYSIS ON CASTING BY SIX SIGMA - QC

DEFECT ANALYSIS ON CASTING BY SIX SIGMA - QC TECHNIQUES TO MINIMIZE THEDEFECTS AND IMPROVE THE PRODUCTIVITY IN OIL PUMP CASTINGas to attenuate the prevalence of defects and increasethe letter level of sand casting method. In today’schallenging market, each organization is trying torealize higher quality and productivity. this may besimply achieved if you concentrate on the reductionin numerous defects that inflicting rejection of theelements. this is often the foremost viable strategyand it'll conjointly lead the organization towardseffectiveness in competitive market. the firstobjective of this Study is concentrated on RejectionReduction in case oil pump Blow Hole Rejectionthrough Six sigma – QC Techniques. The objectiveshere are improved cooling system in die, Separatecooling line for OCV hole core pin, Parameter settingchanges, Implementation of squeeze system toreduce internal porosity.MATERIALS AND METHODSPareto chartThe diagram is a graphical representation of the law.The various categories are listed across the bottomof a graph, then the cumulative totals are plottedas percentages. Starting with the largest numberto the left, the diagram is formed. It is clearly seenthat a small portion of activities are more importantand contribute most towards the objective. A largeproportion is trivial in their contribution. It canbe shown quickly which category is clearly moreimportant. Thus, the chart helps to identify the ‘VitalFew from Trivial Many’ and to concentrate on thevital few for improvement. Six-pack charts includedifferent six different packs and are provided in theformat of one diagram.Control chartsAmong seven SPC tools, control diagram is themost important part. Control chart based uponmeasurements of quality characteristics such asSqueeze Time, Weld Time, Hold Time and Pressureare called as control charts for variables. The processvariations are controlled using control diagrams, anddefective products are avoided by some preventiveactions. Here, it means controls diagrams R, and Xare the most popular control charts.Control charts R, XX charts control the process average whereas Rcharts control the process dispersion or variability.If X1, X2 Xn is a sample with n members for givenquantitative attributes, and then the mean for thesesamples are as follows:x1 x 2 x3 . xn Xn1716According to the central limit theorem, selectingappropriate sample size, distribution X tends tonormal distribution. Thus, 99.72% of data is placedwithin the following control limits.ucl µ x 3σ xcl µ xlcl µ x 3σ xHence, control limits for X diagram can bedetermined, having the mean and standard deviationfor Xs society [14].Statistical principles for R (range) control chartsR is applied as an estimate for standard deviation. Theprocess variability are controlled, depicting R valueson the control diagram. This control diagram is calledR diagram. Limits calculations for these diagramsare performed as easily as X diagram calculations,assuming that Ri refer to variations between themaximum and minimum data in i-th sample. Whenthe control limits of diagrams are calculated usinginitial samples, it is necessary to depict the mean andrange oversamples on X , R Diagrams and connectthe points to each other on diagrams for studyingthem. If the points on diagrams show an out ofcontrol state or a non-random pattern, causes mustbe studied. Other on diagrams for studying them. Ifthe points on diagrams show an out of control stateor a non-random pattern, causes must be studied.Dispersion chartClearly, sampling must be performed during variousperiods with few numbers so that data would havethe most important attribute for comprehensiveness.Random sampling in long period of time is requiredto obtain better results. It is recommended that thenumber of data in each group not to exceed fromfive. Dispersion diagram shows data by the formatof its group as well as the data in each group whichis in vertical line. Dispersion diagram indicates thequantitative level of data in each group. It also showshow far data is quantitatively close to each other. Itallows us to compare different groups with eachother to identify the relationships among them interms of their component numbers. Finally, it helpsto compare process performance during variousperiods and evaluate it implicitly.HistogramHistogram represents variation in sets of datagraphically. Histograms are bar graph displayi.e., vertical rectangles drawn side by side. Themost generally used graph for showing frequencydistributions, in a set of data occurs. Many data

SIVAM ET AL.1717are categorized in a specific format in order thatthe problem can be understood and analysed moresimply. It is obvious that data grouping and graphicdisplay help us significantly to decide logically andeffectively. It provides an image for data, by whichthree following attributes can be understood andobserved more simply: a) Form of data frequencydistribution b) Location with central tendencyfor distribution c) Dispersion by distributiondevelopment. Usually, in the best situation, acommon pattern is the bell-shaped curve known asthe “normal distribution.” In a normal distribution,points are as likely to occur on one side of the averageas on the other [15].Cp, Cpk indices (process capability indices)Process capability is one amongst the necessarythings in production associated with Casting. Amethod is also controlled statistically, however itsproduct might not be within the vary being thoughtof by the client. Victimisation method capabilityindices, a selected production vary is decided for apart as a fraction of its tolerance varies. Productionmethod capabilities are often known victimisationCp index:usl lslCp 6σIs an estimate of standard deviation for the societyof production process. It is given by: σ nσ x[n( x x )]2n 1Different values calculated for Cp index indicatemethod state as follows:1. Cp 1 has method capability for manufacturinga part within the vary being thought of by theattachment Quality.2. Cp 1 has method capability for manufacturinga part within the vary being thought of bythe attachment Quality with the likelihood ofmanufacturing a defective part.3. Cp 1 has not method capability for manufacturinga part within the vary being thought of bythe attachment Quality and a defective part isdefinitely made by this method [16].Considering Cp formula, decreasing the vary ofproduction method is one amongst the factorseffective on rising Cp index. Thus, the smallermethod dispersion or is, the upper productionmethod capability is. Cp index, freelance ofproduction method vary is placed during whicha part of tolerance vary, will have numbers largerthan one, i.e., it should be Cp 1 whereas all madeparts square measure outside of the tolerancevary. Because of this defect in Cp, another index isintroduced to contemplate the assembly methoddispersion, likewise on appraise the method locationto tolerance vary. This issue, called Cpk, is displayedas follows:min{(usl x ), ( x lsl )} 3σIn the above relation, is that the variance forproduction method, also being used in Cp formula.If the production mean is found within the middle oftolerance vary, Cp Cpk; otherwise, Cp Cpk. Cpkshows method capability for manufacturing a givenattribute additional exactly than Cp [16].C pk Process Capability AnalysisAccording to Montgomery (2000) the subsequentcrucial assumptions are created and valid beforeestimating the method capability for Spot attachmentoperation. The assumptions here square measureone. The process should be in state of appliedmath management. 2. The standard characteristicincorporates a distribution. 3. Within the case of 2sided specifications, the method mean is targetedbetween the lower and higher specification limits.4.Observations should be random and independent ofevery alternative.CASE STUDYThe CompanyA case study has been carried out in a small-scalebusiness that is manufacturing numerous Castingfor the Die Casting Machine. This company isAN ISO 9001:2008 certified and comprising wellequipped machine tools. Their core ability lieswithin the production of big selection of product likecasting numerous styles of Die Casting Machines.This company is producing their numerous productswith 1st process as pressure die casting administeredon cold chamber pressure die casting machines andthat they face the matter of rejection and make overin their numerous products. supported sales worthof assorted product, product named pump is chosenfor reducing rejection/rework.Rejection Data (Before taking action)The various experimental methods and techniquesfollowed in the present investigations are describedin this section (Table 1).Rejection Paretto Diagram for the Month of TrialMonth 1From the above (Fig. 1), paretto diagram shows the

DEFECT ANALYSIS ON CASTING BY SIX SIGMA - QC TECHNIQUES TO MINIMIZE THEDEFECTS AND IMPROVE THE PRODUCTIVITY IN OIL PUMP CASTING1718Table 1. Rejection data.YP8 case casting rejection summaryRejection phenomenonS. no123456789Trial periodsTrail month 23416137107216764432851309527Trail month 141406310000424102541Blow hole in OCV holeBlow hole in OCV milling faceBlow hole in oil gallery holesBlow hole at Mounting faceBlow hole in rotor areaBlow hole in dia 53.0Blow hole at bracket side engine mounting faceBlow hole at engine mounting rotor sideM6 blow holeTotal casting rejected due to blow holeTotal inspected qtyTotal blow hole rejection %TotalTrail month 3 8202095327773972528Defect wise Pareto diagram - YP8 Case83.077.880.072.1800Rej Qty lelowarerotorOCVholea0face200BCumulative Rej %1000100.0100.099.598.996.894.191.087.2DefectFig. 1 Rejection Paretto diagram for the month of July 2014.Fig. 2 Inspected vs. blow hole rejection.major rejection is due to blow holes. So investigationswere done by blow holes (Fig. 2-5).Fig. 3 Blow hole rejection % month wise.Cooling SystemThe cooling tube inside, the core pin is only Ø3 mm

1719SIVAM ET AL.Fig. 4 Blow hole location on machined surface.Fig. 5 Internal porosity in OCV area.Fig. 6 Core pin cooling system.Fig. 7 Insert cooling system.Fig. 8 Flow analysis at plunger 440 mm and 447 mm.

DEFECT ANALYSIS ON CASTING BY SIX SIGMA - QC TECHNIQUES TO MINIMIZE THEDEFECTS AND IMPROVE THE PRODUCTIVITY IN OIL PUMP CASTINGFig. 9 Flow analysis simulation at plunger 527 mm and 562 mm.Fig. 10 Flow analysis simulation at plunger 611 mm.Fig. 11 Man machine environments.1720

SIVAM ET AL.1721which is not sufficient to reduce its temperature. sothe cooling tube diameter to be increased (Fig. 6).The spot cooling depth is 80 mm far from the cavitysurface it cannot act effectively to reduce that surfacetemperature. So the cooling depth to be increased(Fig. 7).Flow Analysis (Simulation vs. Actual)Even after the complete filling of the casting the OCVarea (heavy mass area) is in negative cast pressurewhich leads to blow hole and leak (Fig. 8-10).Process parameters used before taking action (Fig.11) and Table 2.ACTION TAKENCooling system improvedCore pin cooling hole ID increased from Ø8 mm toØ10 mm. Cooling hole depth increased from 300 mmto 362 mm (Fig. 12).SQUEEZE SYSTEM IMPLEMENTEDSqueeze CastingSqueeze casting could be a die casting methodsupported slower continuous die filling and highmetal pressures. laminar die filling and squeeze,which is that the application of pressure throughoutsolidifying, ensures that the part is free fromblowholes and consistency. This technique producesheat-treatable parts that may even be employed insafety-relevant applications and are defined by theirhigher strength and ductility when compared withtypical die cast components (Fig. 13).Table 2. Process used before action.Setting ParameterOrigin (mm)Shot High speed Position (mm)Shot DS Position (mm)Shot Intensify Speed position (mm)Intensification Pressure (kg/cm2)Spray Fixed Portion (s)Spray Moving Portion (s)Low Speed Velocity (m/s)High Speed Velocity (m/s)Metal temperature (oC)Shot ready Time (s)Cooling Time (s)Inten Time (ms)Biscuit thickness (mm)Cycle Time (s)Locking Force (kgf/cm2)Laddle Waiting Time (s)YP8 Process Parameter SettingSet No 1Set No 2.462.76806802117171381602626959585085051.8Set No g. 12 OCV hole core pin cooling tube diameter increased from Ø3 mm to Ø6 mm.Set No 46354905405903001.82.30.183.168011713826958501.8

DEFECT ANALYSIS ON CASTING BY SIX SIGMA - QC TECHNIQUES TO MINIMIZE THEDEFECTS AND IMPROVE THE PRODUCTIVITY IN OIL PUMP CASTINGFig. 13 OCV hole core pin cooling tube diameter increased from Ø3 mm to Ø6 mm.Fig. 14 Samples produced in setting-1.Fig. 15 Samples produced in setting-2.Fig. 16 Samples produced in setting-3.Fig. 17 Samples produced in setting-4.1722

SIVAM ET AL.1723Benefits of Squeeze CastingUsing this method it's possible to produce heattreatable castings (not possible in typical die castingdue to air entrapment). it's become called ‘squeeze’casting because the casting is squeezed during acontrolled fashion underneath high to finish thefilling of the die in (Fig. 14-17). The applied pressureand fast contact of molten metal with the die surfaceproduces a fast heat transfer condition that yieldsa pore-free, fine-grained casting with mechanicalproperties approaching those of a molded product.Squeeze casting offers high metal yield, minimumgas or shrinkage, low consistency and an excellentTable 3. Process parameter setting.Setting ParameterLow Speed Velocity (M/S)High Speed Velocity (M/S)Shot High Speed Position (Mm)Shot Intensify Position (Mm)Inten Time (Ms)Spray –Fixed Portion (S)Spray –Moving Portion (S)Metal Temperature ( C)Squeeze Delay Time (S)Sueeze Time (S)Air Blow (S)YP8 Process Parameter SettingSet No 1Set No 12101022Set No 30.402.52460560894466525204Set No 40.302.9460560892366525204Table 4. Rejection summary.YP8 Case Casting Rejection SummaryS. no Rejection phenomenon123456789Blow hole in OCV holeBlow hole in OCV milling faceBlow hole in oil gallery holesBlow hole at Mounting faceBlow hole in rotor areaBlow hole in dia 53.0Blow hole at bracket side engine mounting faceBlow hole at engine mounting rotor sideM6 blow holeTotal casting rejected due to blow holeTotal inspected quantityTotal blow hole rejection %Trail Month 1Trail Month 1.06Total rejectiontso far6644239565137737357282671.26Table 5. Rejection summary of blow hole location.S. no Blow hole location123456789Blow hole in OCV holeBlow hole in OCV milling faceBlow hole in oil gallery holesBlow hole at Mounting faceBlow hole in rotor areaBlow hole in dia 53.0Blow hole at bracket side engine mounting faceBlow hole at engine mounting rotor sideM6 blow holeOverall blow hole rejectionBlow hole rej% before Blow hole rej % After (sep’14 (jun’14 30.10.050.10.020.70.021.40.1328.31.26

DEFECT ANALYSIS ON CASTING BY SIX SIGMA - QC TECHNIQUES TO MINIMIZE THEDEFECTS AND IMPROVE THE PRODUCTIVITY IN OIL PUMP CASTING1724MONITORING AND DATA COLLECTIONRejection Data CollectionGrapical comparison of before and after processcomparison (Fig. 18).Over all blow hole rejection comparison before andafter (Fig. 19).CONCLUSIONFig. 18 Graph comparison between before and after actiontaken.Fig. 19 Over all blow hole rejection between before andafter.surface end, combined with lower in operationprices. Squeeze casting decreases the proportion ofconsistency and will increase density likewise as grainsize. This fine grain size improves the mechanicalproperties of the squeeze solid part. Another massiveadvantage of squeeze casting is that the risk ofvictimisation pre-forms (high-porosity bodies madeof specially selected materials). By infiltrating thesewith liquid metal underneath high it's doable toadditional improve the properties of the aluminumthrough composites and, hence, produce operatingsurfaces that are extraordinarily hard wearing. Ofthe numerous casting techniques offered, squeezesoliding has bigger potential to form less defectivecast parts. Since the as-fabricated parts can be readilyused in service.PROCESS PARAMETER CHANGEDTrial taken in four different setting to freeze theprocess parameter (After providing squeeze system)By verifying the above cut section samples thesetting-1 is seems to be better to compare withthe other three setting so it is freeze as the processparameter (Table 3-5).This study conferred application of a six sigmamethodology to identify the problems during a castingprocess and solve the problem by determinative theoptimal operation parameters for reducing Sandinclusion defect. The blow hole rejection level hasbeen with success reduced in casting part from 28.3%to 7.1%. so the productivity has been accumulatedto fulfill the customer requirement. From the higherthan project/analysis the importance of coolingsystem in die, die design and machine methodparameter freezing. And for the primary time inour company we had made a squeeze casting that isnew the corporate history. Identical system are oftenhorizontally deployed for the forthcoming crucialparts.REFERENCESAbidakun, O.A., Leramo, R.O., Ohunakin, O.S.,Babarinde, T.O. and Ekundayo-Osunkoya, A.O.(2014). Quality improvement of foundry operationin Nigeria using six sigma technique. SENRAAcademic Publishers, British Columbia. 8 : 2751-2760.Antony, J. and Banuelas, R. (2002). Key ingredientsfor the effective implementation of Six Sigmaprogram. Measuring Business Excellence. 6 : 20-27.Bessant, J. and Francis, D. (1999). Developing strategiccontinuous improvement capability. InternationalJournal of Operations & Production Management. 19: 1106-1119.Bhupinder, S. (2014). Determination and correctionof sand casting by implementation of DMAIC toolof six sigma. International Journal of Research inEngineering & Applied Sciences. 4.Binu, B.V. and Anilkumar, K.N. (2013). Reducingrejection rate of castings using simulation model.International Journal of Innovative Research in Science.Engineering and Technology. 2.Breyfogle, F.W. (1999a). Implementing Six Sigma –smarter solutions using statistical methods. Wiley,New York, NY.Caulcutt, R. (2001). Why is Six Sigma so successful?Journal of Applied Statistics. 28 : 301-306.

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DEFECT ANALYSIS ON CASTING BY SIX SIGMA - QC TECHNIQUES TO MINIMIZE THE DEFECTS AND IMPROVE THE PRODUCTIVITY IN OIL PUMP CASTING SUNDAR SINGH SIVAM S.P 1*, .SARAVANAN2, N. PRADEEP2, S.RAJENDRAKUMAR , AND K. SATHIYAMOORTHY1 1Department of Mechanical Engineering, SRM U