DESIGN & SIMULATION OF A CASTING

DESIGN & SIMULATION OF A CASTINGSubmitted by,Pranjal Jain (10D100027),Shubhakar Raju(10D100039)

ME 659 Course Project

PART - VIEWS

CONTENTDesigning the selected casting by Hand CalculationsPart details, Complexity, DrawingDesigning Core, Feeder, Neck, Feed-aids & GatingDesign Considerations in Casting(Parting line, Feeder, Sprue, Gate & Runner types & locations)Yield, Solidification time, Cost estimationCasting Simulation of the part by Auto-CastPart properties, Materials chosenDesigning Core, FeederSelection of Feed-aidsPart with Gating system (Basin, Runners, etc.)Feed-paths, Solidification, Shrinkage & Flow SimulationsComments on the partComparison between hand calculations & Auto-Cast simulationCost estimation & OptimizationDesign by HAND CALCULATIONSCasting Part propertiesDimensions, DrawingsMaterialsShape ComplexityDesignCore & Core PrintFeederNeckFeed-aidsGatingEstimationCasting YieldSolidification timeCost

PART PROPERTIESDimensions (Bounding Box) 650 x 875 x 500Volume (Part) = 118518 cc = 0.12 m3 app.Bounding Box Volume = 284375 cc = 0.284 m3Assumed Material of Casting = Cast Iron 3.5 CEDensity = 7176 kg/m3Part Weight = 850.45 kgPart Surface Area = 25881.6 sq .cm = 2.5 m2Hole Volume = 41,459 cc = 0.0415 m3 app.Max & Min thickness = 15 cm & 0.5 cm5PART PROPERTIESCasting, Core, Sand MoldCastingCast Iron 3.5 CEDensity = 7176 kg/m3 (Solid) ; 7150 kg/m3 (Liq.) Specific Heat = 471 J/kg-KThermal Conductivity = 36 W/m-KFluidity = 900mmLiquidus T = 1221 0CSolidus T = 1110 0CPouring T = 1370 0CWeight = 850.5 kgPART PROPERTIESCasting, Core, Sand MoldCore CO2 CuredSpecific Heat = 735 J/kg-KK (Thermal Conductivity) = 0.98Density = 1770 kg/m3Specific Heat = 735 J/kg-KMoldGreen SandSpecific Heat = 1.1kJ/Kg-KCompressive Strength = 13 kPaK (Thermal Conductivity) = 0.60 W/m-K

PART SHAPE COMPLEXITYCVR ,Volume Ratio = 1 - (Vol. of Part/ Vol. of Bounding Box) = 0.58 CAR , Area Ratio = 1 - (SA Sphere of Same Vol. / SA of Part) = 0.55 CTR , Thickness Ratio = 1- Min thick. /Max thick. = 0.66Number of Cores = 1,CNC = 1 [1 / (1 + number of features)]^0.5 = 0.29 CCR , Core Volume Ratio = Core Volume/Part Bounding Box Volume = 0.34

Avg. Shape complexity = (CVR + CAR + CTR + CNC + CCR)/5 = 0.544

DESIGN - CORENumber of Cores = 1Design Consideration Core Print Weight ( Wp ) > Core Weight ( Wb )Core & Print DesignWb = Volume of Core * Density = 0.041 * 1770 = 72.57 kgCore Print Volume > 0.041 m3 (Implying consideration)Safety factor of 1.15 is taken i.e. Wp = 1.15 * Wb

Assuming Dp > Max. Db - Core Dia. = 30 cm & Lp = Dp / 2Weight of print, Wp = 83.46 kgSo, Lp = Wp / Ap = 83.46/(*Dp2/4)/pTherefore, Lp = 25 cm; Dp = 50 cm 9DESIGN - CORESustainability of Core print & Core:Weight of Core print = 83.46 kg * g (Downwards)Weight of Core body = 72.57 kg * g (Downwards)Buoyancy force on the Core = *Vb*g = 297 kg * g (upwards)Net force = Buoyancy Weight in kg NNet force on the Core Print + Body = 150 kg N approx.Compressive stress on mold dictates its safetyDue to core compressive mold stress:d = Net force/ Print Area = 150 kg N/ (*Dp*Lp)Calculated d = 1871 N/m2 = 2k Pa approx. < 13k PaRequired d tCasting)MCasting = Volume / Area of CastingModulus of Casting = 4.8MFeeder > MNeck > MCasting = 5 (Approx.)Assuming, Factor of Safety = 2(Since, thick sections casting modulus is about 7)Feeder type Spherical BottomMFeeder = 2* Mcasting = 10

DESIGN - FEEDERFor this feeder,Mfeeder = (2r3/3 + r2h)/(3r2+ 2rh)Implying, MF = (2r2 + 3rh)/(9r + 6h)Assuming, H= D i.e. h = 2*rMF = 10 = 8/21 * r , r = 28 cmStandard r = 28 cm ; h = 56 cmSince, we are making two castings with one feederFeeder Yield = 2*vc / (2*vc + vF) = (0.12)/(0.12+0.18)Yield = 60 %

DESIGN - NECkNumber of Necks required = 1 per castingMC , Modulus of Part = 5MF , Modulus of Feeder = 10MN , Modulus of Neck > 5 & < 10MN > Mh (Modulus of hotspot)Modulus of hotspot = 7 (Hot spot, thick section)Therefore, MN = 1.2 * MH = 8.4Considerations: MF > MN > Mh > McastingNeck type : RectangularMN = (L*w*d)/(L*2(w+d)) = wd/(2w+2d)

DESIGN - NECKAssuming, w= dMN = d/4 = 8.4which implies d = 33.6 cm (Taking 30 cm approx)30 cm of neck width is comparable with Height of FeederTherefore, we do at least one iterations1st Iteration :New area available for cooling in FeederArea = 3r2+ 2rh wd, Vol. remains sameMF (New) = 11.2 Since, Area of casting is so high = 2.5 m2 >> 0.11m2we need not consider changing modulus of casting in iteration, it remains almost sameFrom new MF = 11.2, r = 31 cm, h = 62 cm (approx.)

DESIGN FEED-AIDSFeed-aids SleevesSleeves & Cover are feed-aids in our castingNumber of sleeves = 1 + 1 CoverModulus Extension Factor = (metal*Cp,metal/ mold*Cp,mold)MEF = 7176*471/1550*1100 = 3.93 = 1.98 (Approx.)For insulation sleeve, MEF = 1.3 1.8After insulating feeder, MF = 1.5*MF1 = 1.5*11.2 = 17 (Approx.)Exothermic Sleeve, MEF = 1.5 1.8For that sleeve MF = 22.4 (Approx)DESIGN - GATINGGating System Constituents: Choke, Sprue (Exit, Entry, Well), Runners, GatingGeneral cross-sections assumed, Diverging gating system is assumedFor Cast Iron < 10 Tons ; Medium thin wall partsGating Ratio = As: Ar : Ag = 1: 0.9: 0.5Gating is done for two castings together Filling Time CalculationsWeight of Gate, Wg = 10% (Wc + WF) = 0.1 (850*2 + 1275) kgWg = 301 kgTotal weight = WF +Wc +Wg = W = 3311 kgFilling time (f )= Ko (Kf Lf / 1000) (Ks + Kt t / 20) (Kw W)pWe know for CI,Ko = Kf = Kw = 1, Lf = 900 mm, Ks = 1.1, Kt = 1.4, p = 0.4

DESIGN - GATINGf = 70 secAverage poring Rate = W/ f = 43 kg/sChokeVelocity VCh= Cd(2)0.5 H = Total height of Pouring = Hsprue + Hbasin + Hpouring = 0.6 mAssuming,Cd = 0.8 , Re = vd/ where d = 30 mmVch = 0.8*(2*9.8*0.6)^0.5 = 2.75 m/sRe = 7150x2.75x0.03/2x10-5 = 2.94x 107Choke Area Ac = / VCh= 21.8 cm2 Ac =/4 * Dc2 ; D = 5.27 cmSprue ExitAssuming, H2 = 0.6 m Total height, H1 = 0.2 m Basin heightGating ratio , As: Ar : Ag == 1 : 0.8 : 0.6DESIGN - GATINGAS = AC = 21.8 cm2 and DS = DC = 5.27 cm Sprue Design (Entry)Ap(H1)^0.5 = As(H2)^0.5 where H1= 20 cm, H2= 60 cmAp = 37.8 cm2 = /4 * 2 ; dp = 6.94 cmRunner DesignAr : As= 0.8 : 1 , Ar= 0.8 x As Ar = 17.44 cm2Runners area cross section SquareSquare Area = Ar = 17.44 cm2 ; Side = 4.2cmGate DesignAg : As= 0.6 : 1Ag= 0.6 x As ; Ag = 13.1 cm2Circular gating cross-section, Ag= 13.1cm2 = g2 / 4, dg = 4.08 cSprue Well (Assuming, Dw= 2 x Ds , Hw = 2 x Dr)Dw= 2 x Ds, Ds= 5.27 cm, Dw=10.54 cmHw = 2 x Dr , Dr =4.2 cm, Hw= 8.4 cm

18YIELD & SOLIDIFICATION TIMECasting Yield = Part Weight / Total WeightPart Volume = 0.12*2 m3 (Two parts in one casting),Total Volume = (0.24 + 0.18 + 0.042) = 0.462Yield = 0.12*2/(0.12*2+0.18+0.042) = 52 %Solidification time (s)=[cast[L+Ccast(TpourTsol)] /1.128[(KmoldxCmoldxmold)^0.5(TinTatm)]*(V/A)]2Therefore, s = [7176*(230.12 KJ+471*(1370-1110) J) *5*0.01 /1.128(0.6*1100*1551)^0.5(0.9*1110-25)]2s = 113.52 = 12882 s = 3.6 hrsSimulation Report- Auto CASTCast Metal: Cast Iron- CI 3.5 CEDensity 7176kg/m3, Liquidus Temp: 1221 oCPart Dimensions: 500mm X 875mm X 649 mm ; Part Surface Area: 2.59 m2 Min Thickness: 26.25mm; Max Thickness: 183.75mmPart Weight 869.90 Kg Mold(sand Mold)Dimensions : 2100mm X 2100mm X 837 mmCavity- Wall Gap : 93.50 mmCavity Cavity Gap: 503.94mmMetal/Mold Volume: 15.35 % Mold Elements: 4 Contd..CoreMaterial CO2 Cured; Density 1770 kg/m3Weight 105kg; Volume= 593438.68 cm3Feeders Total Weight = 1.58 ton, Volume = 0.22 m3 Diameter = 800mm, Height = 500mmNumber of Necks= 2 (one per casting)NeckShape rectangular, length at part& feeder = 300mm, Breath = 150mm

Gating Pouring Temperature = 1370 C ; Mold Filling Time = 43.33sSprueHeight= 564.21mm, Cylindrical, Top Dia= 142.20mm; Bottom Dia= 97.63mmPouring BasinDimensions = 357mm X 238.61mm X 178.96 mmWellDiameter = 163.83mmHeight = 122.87mmRunners (2)Width = 73.01mm; Height = 73.01mm ; L1= 435mm; l2 = 476.15mmOverall

Gates

Part Properties

Core Design

Feed Path

Solidification

Flow Simulation

Cost Analysis

5.00 4.00 4.00 750 RsTotal Cost: 83957.59 Rs/part Comparison ParametersHand CalculationsAuto-cast SimulationRemark Dimensions650 x 875 x 500mm650 x 875 x 500mmSameFeeder Yield60%52.42%Compromise due to large size Feeder DimensionsD=480mm H=560mmD=800mm, H = 500mmBigger feeder for hotspot removalNeckW=B=336mm D=120mm B = 300mm l =150mm, D=116mmSimilarSprue WellD=105mm, H= 84mmD = 163, H = 123mmAuto-cast filling time is lower, Gating system is largerGateDg = 40.8mm D=60mmSpruve Exit and EntryDin 69mm, Dout = 52.7mmDin= 142mm Dout = 97Conclusions Both hand based calculations and Autocast simulations based designing process was carried out Successfully designed the core, feeding, gating system through an iterative process Various positions and sizes of feeder were tested and an optimum design was finalized using simulationsTwo castings were served by single feeder and the cavities are arranged in a fashion facilitating efficient gating design and mold utilization Porosity defects can further be reduced using internal chills in the top part of casting, but it will increase the cost Hand calculations have greater deviations from auto cast simulations due to the large size of the part