mould hpdc runner

Upload: sahri-karim

Post on 05-Oct-2015

200 views

Category:

Documents


4 download

DESCRIPTION

no rip

TRANSCRIPT

  • CAEDSMouldDesign

    HPDCrunnerandgatingsystemdesignTampereUniversityofTechnologyTuulaHk

    Highpressurediecasting(HPDC)diegatingsystemconsistsofabiscuitorasprue,arunner,agate,overflowsandvents.Thebiscuit forms in the cold chamberHPDCmachineshotsleeveandsprue inthehotchamberHPDCdiespruebushing.Spruebushing isanactive element inguiding themetal flow.Cold chamberHPDC shotsleevedoesnothingmuchbutoffersaclosedplacetoshootthemetalfrom.

    There are two basic runner types: tangential and fan runner. (See images below.)Runner isacarefullydesignedpartof theHPDCdie. Itcontrols themetal flowbyacceleratinganddirectingittotherightplacesinsidethedie.

    Overflowsgathertheoxidisedfrontofthemetalandfunctionasheatstoragesnearthinand/ordistantpartsofthecasting.Ventsleadgasesoutofthediecavity.Shortdiecavity fill timerequiresmoregenerousventing than longer fill time.Ventsandoverflowsattractthemetalfronttothewanteddirections,butmainlyitistherunner,whichdoesthedirecting.

    Image1. FantyperunnerwiththebasicelementsinHPDCdiegatingsystems.Coldrunnergatingsystemontheleftandhotrunnersystemontheright.

    Image2. TangentialrunnerforacoldchamberHPDCdie.

    Both runner types arewidely in use.Tangential runner gives better possibility toguide themetal flow in the runner and inside the die cavity. It also gives betterpossibility tocontrol themetalvelocity in thegateandraise thevelocityashighaswanted.

    HPDCrunnerandgatingsystemdesign1

  • CAEDSMouldDesign

    HPDCrunnerandgatingsystemdesignconsistsofthefollowingsteps:

    1. Analysisofthemetalflow2. Selectionofthebestplaceforthegateononesideofthecastingandventson

    theoppositeside3. Calculationofamaximumdiecavityfilltimeandselectionofagatevelocity4. Divisionofthecastingintogatingsegments5. Calculationofoverflowvolumespersegment6. Calculationofatotalgateareaandselectionofagateheight7. PQ2analysis8. Cavityfilltimeandgateareacalculationsbysegment9. Selectionofarunnertypeandshapingtherunner

    Analysisofthemetalflow

    HPDCrunnerandgatingsystemdesign2

    Anidealcastingdesignallowsthemetaltopassthediecavitywithdirectandclearroutes.Usuallythereisaneedtocompromise.Onlyseldomitispossibletodesignanidealgateandrunnersystem.(Seeimages.)

    Image3. Acupshapedcastingwithaflange.Metalflowstartsfromthepartinglineandfinishestothepartinglineontheoppositeside.Nolargebossesoutsideorinside.Clearflowpatternandenoughspaceforthegate.

    Image4. Aflatcasting.Nohighbosses.Clearroute.Thereareblindspotsbehindtheholesintheendofthemetalflowpath.Metalentersthelastpointfromtwodirectionsanditispossiblethattherewillbeanareawherethemechanicalpropertiesarenotasgoodasontheotherareasofthecasting.

    Image5. Acastingwithcoolingribs.Thisisnotanoptimalsolution.Ribsformclosedcavitiesoutsidethemainrouteofthemoltenmetal.

    Runnerandgatingdesignsteps

  • CAEDSMouldDesign

    Image6. Bettertogatefromthisdirection,butthereisnotasmuchspaceforgatingasinthecaseabove.

    Image7. Ablindboss.Aclosedshapeabovethecavitysurfacewithoutventing.Notagoodsolution.

    Image8. Betterthanabove.Metalflowsaroundtheprojectedshapesandpushesgasestowardventingintheoppositesideofthecavity.

    Image9. Betterthantheexampleintheimage7.Metalflowsthroughtheribsandgasesouttowardstheventingintheoppositeside.Ribscancausesomemoredifficulties,forexampletherecanbeshrinkmarksonthebottomofthepart.Ribsarerelativelyexpensivetomachinetothemould.

    Thepartdesigner shouldhavehadconsidered thepart shapes from thecastabilitypointofview.Usuallythereisatleastonenegotiatingandconsultingroundduringwhich thehighpressurediecasting foundrypersonnelgivesadvice inshaping thepartforcastability.Iftheseconsultingphasesarepassed,thegatingsystemdesignerdoesnothaveanyotheroptionthantotryfindingthebestpossiblepathforthemetalto flow through the cavity.Thispath sets the bounds forplacing gates to thediecavity.

    Selectionofthebestplaceforthegateononesideofthecastingandventsontheoppositeside

    Allcommoncastingalloystendtoshrinkduringsolidificationandcooling.Ifnothingisdone, the finished castingwillhavevariousdefects caused by the solidificationshrinkage.Thesedefectsarebasicallyhollowsections,porosityandsinksofdifferentsize.Insandcasting,gravitydiecasting,lowpressurediecastingandforexampleininvestment casting themould is equippedwith risers,which feed liquidmetal forcompensating the solidification shrinkage. Risers are conical protrusions placedabove theheaviestand lastsolidifyingsections in thecastpart.The lastsolidifyingsectionsshouldnotbesurroundedwiththinnersections,becausethethinwallswillsolidifyprematurelyandblocktheflowpathofthefeedingmetal.

    HPDCrunnerandgatingsystemdesign3

    USERTypewritten Text

    USERTypewritten TextAmet-sahri, sampe hal 11

  • CAEDSMouldDesign

    Highpressurediecastingisanexceptionamongcastingmethodsinthattherearenorisers.Thefeedingmetalisforcedthroughtheingatewithaplunger,basicallyusingthesamerouteasduringthefillingphase.Forthisreasonthecastingdesignershouldshape the castingwith a path of decreasing sections starting from the ingate andendingtooverflowsandvents.Uniquewallthicknesswillalsodo,butusuallythereareboththinnerandthickersections.

    If the part iswisely designed there is a clear path ormultiple paths through thevolume.Thegatesareplacedonthepartingsurfacetowardsthethickestsectionsanddirectedawayfromcoresandverticalwallsifpossible.Ventsareplacedtotheopposite side of thepart. Select gate andventpositions in order tominimize the flowlengthacrossthediecavity.

    Tangentialgatingsystemgivesgoodpossibilitiestodirectthemetalflowwherethefangategivesonlyalittleornopossibilitiesfordirecting.Bothgatetypescanbeusedwithmultiplerunnersordividedrunners.Ifthepartisdesignedwithmultiplethicksections,it ispossibletodividetherunnerandplaceagatetowardseachthicksection.(Seeimagesbelow.)

    HPDCrunnerandgatingsystemdesign4

    Image10. Dividedrunnerwithtwogates.Multiplecavitydierunnersaredesignedinasimilarway.

    Image11. Adirectedmetalflowfromatangentialrunner.

    Avoidtwometalfrontstoencounterindistancefromthegate(Seeimage4).Thisisanunwanted situationon thewhole,but sometimesnotavoidable.For this reasonframeshapedcastingsshouldbegatedfrominside.Weakpointsincentergateconstructionarethatitdoesnotallowmultiplecavitiesandthattheflowvelocitydropsinsidelongrunnersbeforethemetalentersthediecavity.Largeopeningscanalsobeprovidedwithrunners.

  • CAEDSMouldDesign

    HPDCrunnerandgatingsystemdesign5

    Calculationofamaximumdiecavityfilltimeandselectionofagatevelocity

    FilltimeThecastingshouldhaveenoughspaceonthepartinglineforthegateandvents.Thegatelengthisthegateareadividedbythegatethickness.Thegateareadependsonselecteddiecavity fill timeandgatevelocity.Diecavity fill time isselectedon thegroundsof:

    Thinnestcastingwallthickness:Thickwallallowslongerfilltimethanathinwall.Thinwallstendtosolidifyprematurelyifthefilltimeistooshort.Alsotheflowlengthiscritical.Iftherearelargeareasofthinwallsorthethinwallsareindistancefromthegate,thefilltimemustbeselectedshorter.

    Thermalpropertiesofthecastingalloyanddiematerials:Liquidustemperature,widthofthesolidificationrangeandthermalconductivityofthemouldmaterial.Theseinfluencethesolidificationtime.

    Combinedvolumeofthecastingandoverflows:Thinwallcastings,castingswithlongflowdistancesthroughthecavityandcastingswithspecialsurfacequalityrequirementsneedlargeoverflows.Largevolumeofthemetalisabletokeeptheheatlongerthanasmallervolume.

    Percentagesolidifiedmetalallowedduringfilling:Thebetterthewishedsurfacequalitythelesssolidifiedmetalisallowedandtheshorterthediecavityfilltime.

    OneofthebestknownformulasfordeterminingdiecavityfilltimeistheNADCAfilltimeequationbyJ.F.WallaceandE.A.Herman1:theequationtakesslightlydifferentformsindifferentliterature.ThefollowingequationandparametersaremodifiedfromMikeWard:GatingManual,NADCA,USA,2006.

    t=maximumfilltime,sK=empiricallyderivedconstantrelatedtothethermalconductivityofthediesteelT=characteristicthinnestaveragewallthicknessofthecasting,mmTf=liquidustemperature,CTi=metaltemperatureatthegate,CTd=diesurfacetemperaturejustbeforetheshot,CS=percentsolidsattheendoffill,%Z=solidsunitsconversionfactor,Cto%,relatedtothewidthofthesolidificationrange

    Thepartoftheequationbetweenthebracketssetsarelationbetweentheconsumableheatduringthecavityfilltimeandthetemperaturedifferencebetweentheminimumflow temperatureanddiecavitysurface temperature.ConstantKrelates this to thediematerialthermalconductivityandTtothethinnestwallthicknessesofthecasting.

    1MikeWard:GatingManual,NADCA,USA,2006.

    TTTSZTT

    Ktdf

    fi

    +=

  • CAEDSMouldDesign

    ConstantKis:

    0,0312s/mmbetweenAISIP20(prehardenednitratingplasticmouldsteel)steelandzincalloys

    0,0252s/mmbetweenAISIH13(hotworkingtoolsteelalloyedwithchromium)andAISIH21(hotworkingtoolsteelalloyedwithchromiumandtungsten)steelandmagnesiumalloys

    0,0346s/mmbetweenAISIH13andAISIH21steelsandzinc,aluminumandbrassalloys

    0,0124s/mmbetweentungstenandmagnesium,zinc,aluminumandbrassalloys

    SolidifiedmaterialcanbeallowedaccordingtotheTable1.

    Table1. Recommendedpercentageofsolidifiedmaterialasafunctionoftheaveragethinnestwallthickness.Ifthereisaneedtohavegoodsurfacequalityinthecasting,uselowervalues.MikeWard:GatingManual,NADCA,USA,2006.

    Aluminum Magnesium Zinc< 0,8 5 10 5 - 15

    0,8 - 1,25 5 - 25 5 - 15 10 - 201,25 - 2 15 - 35 10 - 25 15 - 30

    2 - 3 20 - 50 20 - 35 20 - 35

    Wall thickness, mm

    Recommended amount of solidified material (S), %

    ConstantZis:

    4,8C/%foraluminumalloysASTM360,380ja384,allundereutectic,lessthan12%SicontainingAlSi(Cu/Mg)alloys

    5,9C/%foraluminumalloyASTM390,overeutecticAlSi(Cu/Mg)alloy 3,7C/%formagnesiumalloys 3,2C/%forzincalloys12and27 2,5C/%forzincalloys3,5and7 4,7C/%forbrass

    BrassHPDCdiefilltimecanbedeterminedbymultiplyingthewallthicknesswithaconstant2:

    s

  • CAEDSMouldDesign

    Gasporositycanbereducedwithoutraisingthegatevelocitybydesigningthegateand runnersystem tomaintain smooth,continuous flowprofilesandbydesigningthecastingsothatnobackflowoccurs.Backflowcanoccurifthereareprotrusionsonthewayofthemetalflow(Seeimages39).

    Thefollowingtablepresentsrecommendedgatevelocitiesfordifferentalloytypes.

    Table2. RecommendedgatevelocitiesfortypicalHPDCalloygroups2

    Normal VacuumAluminum 20 - 60 15 - 30

    Zinc 30 - 50Magnesium 40 - 60 (up to 90)

    Copper 20 - 50

    AlloyRecommended gate velocity, m/s

    Divisionofthecastingintogatingsegments

    HPDCrunnerandgatingsystemdesign7

    Gatingsegmentsaretoolsforvisualizationthemetalflow.Basicallytheyareportionsof the castingwheremetalnaturally tends flows toa relatively coherentdirection.Avoidclosedends:Thereshouldalwaysbeaventontheoppositesideofthegatingsegment. Tangential runner gives good possibilities to direct themetal flow. (Seeimages.)

    Image12. Acupshapedcastingwithnarrowribtypeprojectionsinthemiddle.Themetalflowisdirectedthroughtheflatprojectionsinthesidesofthecastingbothinupwardandsidewarddirections.Theribtypeprojectionswillcauseproblems.

    Image13. Overflowsforthecasting.

    Image14. Segmentedcasting.Theribshapedprojectionsformclosedcavitiesinthemiddlesegmentandmakethemetalflowmorecomplicated.Itispossiblethatsomebackflowoccursinthemiddlesegment.Backflowmixesgastothemetalandcausesporosity.

    Image15. Modifieddesign.Thelongribshapeprojectionsarenowsmaller.Metalflowsbettertotherightdirectionsandtherearenoclosedshapes.

  • CAEDSMouldDesign

    Eachgatingsegmentshould:

    provideacoherentandunrestrictedflowofmetalthroughthecavity haveuniquewallthicknessorsectionsofthickerwallstowardsthegateand

    thinnerwallstowardsventing haveaenoughpartinglinetoplacethegateandventing

    Definingtheoverflowvolume

    HPDCrunnerandgatingsystemdesign8

    Overflowsarelocalheatstoragesandalsostoragesofanoxidized,badqualitymelt.Overflowsarenecessary if the castingwall thickness is smallor there isaneed tokeep the castingwarm for some other reasons. The common reason is that somedistantpartshave coredholesaroundwhich themelt flows throughnarrowwallsfrom twodirections.Themelthas tobesufficientlyhot tobeable to forma tightlyknittedwall.Theremightalsobeaneedtomoveahotspotawayfromacriticalareabykeepingsomeotherareanearbywarmforalongertime.

    With a 3DCAD software it is relatively easy to find out the characteristic or thesmallestwallthicknessineachofthegatingsegments.Basedonthisinformation,theoverflow volume is selected (See the following table). If the die is designed for avacuumcastingmethod,theoverflowsaretypicallyrathersmallifexistingatall.

    Table3. Overflow volumes in a conventionalHPDC diewithout vacuum equipments as afunctionofathinnestwallthickness

    Requirements of an excellent surface quality Some cold defects allowed

    0,90 150 % 75 %1,30 100 % 50 %1,80 50 % 25 %2,50 25 % 25 %3,20 - -

    Overflow volume, percentage of the segment volume

    Characteristic (or the smallest) wall thickness in the gating segment, mm

    Overflowsshouldhavetheshapepresentedinthefollowingimage.

    Image16. Theshapeanddimensionsofanoverflow.A=Landlength(25mm);B=Overalllengthoftheoverflowgate(58mm);C=Overflowgateheight(Al0,61,2mm,Zn0,30,8mm,Ms0,81,5mm).Ventheightisasfollows:Al0,100,15mm,Zn0,060,10mm,Ms0,10,15mm.

  • CAEDSMouldDesign

    HPDCrunnerandgatingsystemdesign9

    Calculationofatotalgateareaandselectionofagateheight

    Totalgateareaiscalculatedwiththecavityfilltime,gatevelocityandtotalcasting+overflowsvolumeaccordingtothefollowingformula:

    fillgate

    overflowspartgate tv

    VVA

    += ,

    where Agate=totalgatearea Vpart=partvolume Voverflows=overflowsvolume vgate=gatevelocity tfill=cavityfilltime

    Possiblegate thickness rangedependson the selectedgatevelocity (orviceversa)accordingtothefollowingformula3:

    JTV gg **707,1 ,

    where Vg=gatevelocity(m/s)

    Tg=gatethickness(mm)=alloydensity(kg/m3)J=constant,998000foraluminum,magnesiumandzincalloys

    Theformulagivesalimittothegatethicknessasafunctionofagatevelocity.Itisnotagoodpracticetochoosealowvelocitywithathingate.Typicalgatethicknessis0,83mmforaluminumalloys,0,72,2mmformagnesiumalloys,0,351,2mmforzincalloysandfrom1,5mmupto4mmforbrassalloys.

    PQ2analysisandthemachinelockingforce

    PQ2 analysis matches the selected gate velocity to the HPDC machine plungerhydraulicsystem.Theplungerhydraulicsconsistsofnitrogenbottles,accumulator,computercontrolledvalvesystem,andahydrauliccylindertowhichtheplungerisattached.Thepurposeoftheplungerhydraulics istomovetheplungerandfillthediecavity.(Seeimage)

    Image17. Coldchamberhighpressurediecastingmachineplungerhydraulics.

    Totalgatearea

    Gatethickness

    3Modified tometric dimensioning system fromMikeWard:GatingManual,NADCA,USA, 2006.1,707(or1+1/2)isusedaspowerinsteadof1,71intheoriginalequation.

  • CAEDSMouldDesign

    HPDCrunnerandgatingsystemdesign10

    Plungermovementhasthreephases:

    Slowphaseduringwhichtherunnerisfilleduptothegate. Fastphaseduringwhichthecavityandoverflowsarefilled.Fastphaseisad

    fillthemouldcavityinthecalculatedfilltime. Intensificationphaseduringwhichacastingispressedwithahighpressure.

    atevelocitydependsonthemetalpressureduringthefastshotphaseaccordingtoefollowingformula4:

    Pm=metalpressurePa=metaldensitykg/m3g=gravitationalconstantm/s2Vg=gatevelocitym/sCd=coefficientofdischarge

    haveuniquepressureandvelocityprofiles.Thecoefficientofdishargerepresentsthevariationbetweenmachines.Typicalvalueis0,450,5.

    HPDC foundries analyze theirmachines to find out the dependence between thevelocityandthepressureinsidetheplungerhydraulics.Pmistheoretical,actualvaluecanbedifferent.

    TheHPDCmachinesareclassifiedbytheir lockingforce.Lockingforce istheforce,which resists themouldopening in the endof the shot.At the instancewhen themouldistotallyfilled,ahighpressureformsinsidethemouldcavity.Thepressureisstill increased in the third, intensificationphaseoftheshot.Thesepressuresformaforcewhichisproportionaltotheprojectedareaofthecasting.Projectedareaistheareaofthecastinginthepartingsurfacedirection.(Seeimage.)

    Image18. Projectedareaofthecastingintheimage2.Projectedareaisthecasting,runner,biscuitandoverflowsprojectioninthepartingsurface.

    Metalpressure createsabreaking forcewhich isproportional to theprojectedareawiththeequationF=PxA.ThiscalculationisusedinestimatingtherequiredHPDCmachinesize.Forexampleiftheintensificationpressureis550bar=550x105N/m2,theprojectedareaof1,49dm2createsadiebreakingforceof820kN.Thisforcewouldrequirea82kilotonsHPDCmachine,which isvery small.PresentHPDCmachinesizevariesfrom100to1000kilotons.Theactualclampingforceshouldbeatleast25%higherthanthetheoreticalvalue.

    justedto

    Gth

    HPDCmachinesc

    4MikeWard:GatingManual,NADCA,USA,2006

    Diebreakingforce

    2

    2

    =

    d

    gm C

    Vg

    P

  • CAEDSMouldDesign

    Consequenceofthedependencesbetw

    HPDCrunnerandgatingsystemdesign11

    eenthemetalpressureandgatevelocityandont o is,thatitisnot pressur

    The lifferentparttypesanddifferentalloys.

    ssurefordifferentalloysandparttypes5

    he therhandthegatevelocityandthepressureinsidethediecavityalwayspossibletoproducewidecastingwithhighgatevelocityand/orhighend

    e.Thereisaneedtocompromise.

    fo lowing table presents recommendations for an intensification pressure ford

    Table4. Intensificationpre

    Aluminum and magnesium

    alloysZinc alloys Copper alloys

    Standard parts, no special mechanical o requirements < 400 100 - 200 300 - 400

    echnical parts with special mechanical

    Part requirements

    ation pressure, bar

    r otherTrequirements 400 - 600 200 - 300 400 - 500Parts with pressure tightness requirements, inspection required 800 - 1000 250 - 400 800 - 1000Parts to be chrome plated - 220 - 250 -

    Intensific

    Cavityfilltimeandgateareacalculationsbysegment

    Totalcavityfilltimeandgateareaisdividedtothegatingsegmentsintermsofthevolume of each segment and overflows.Gate are is calculatedwith the followingformula:

    overflowscasting

    overflowssegmentsegmentgatesegmentgate VV

    VVA + )( _A+

    =_ ,

    where Agate_segment= ateareaofthesegmentAgate=total tearea

    Vsegment=segmentvolume Vsegment_overflows =overflowvolumeinthesegment Vcasting=totalcastingvolume

    Voverflows=t wsvo

    gga

    otaloverflo lume

    Ventcrosssectionarea

    Vent cross section area is ingate cross section areadividedby 4. Sufficiently largeventsassurethatair insidethediecavitydoesnotexitwithtoo largevelocity.Vacuumcastingequipmentneedsspecialconsiderations.

    lu,seminar20.22.10.1998,Espoo,Finland

    tensificationressures

    5J.Orkas,edit.E.R.Keil:Painevalumuotinsuunnitte

    Inp

  • CAEDSMouldDesign

    HPDCrunnerandgatingsystemdesign12

    Selectionofagatetypeandshapingrunnersandgates

    Thereare twobasicgate types: tangentialand fangate.Bothgatesareusuallyde

    metalflowthroughthegate(s)isminimal.Tangentialgatescomeintwobasictypes,whichcanbeguidedorunguided:

    continuousdirectedgate dividedundirectedgate divideddirectedgate

    Selectionbetween thegate typesdependson thepartrequirements.Fangate is thesimplest instructureandeasiest tomachine.Theunfavourablecharacteristic is thatmostof the flow comesout from the centreof thegate.Tangentialgatesaremoredifficulttodesignandmachine,butthedesignisflexibleandeasytoadapttodifferenttechnicalrequirements.

    othgatetypescanbedividedintotwosections:

    mainrunners

    atestodiecavities.

    Cro shapeofmThe of th a trapezoidwith sidedraft of 10deg ewidth ratio should be between 1:1 1:3.Typ is1

    Image19. MainrunnerheighthrandwidthWr.Inthisexampletheratioheighttoaveragewidthof1:2hasbeenused.hr=1,Wr=2.

    tionofrunnerbranchesshouldnlargeby530%aftereachcrossingifthedirectionfromgatestowardsthesprueoriscuitisconsidered.Seeimage20nextpage.

    Runnerheighttowidthratios(fanandtangential)

    signedwith converging cross sectional area. Fan gates can be divided into smallopenings,butthepossibilitytoguidethe

    continuousundirectedgate

    B

    gaterunners

    Mainrunnersleadthemetalfromahotchamberdiecastingmachinesprueoracoldchamber die castingmachine chamber to the gate runners.Gate runners lead themetaltog

    sssection ainrunners shape r ion should bee unner crosssectrees.Main runner height to averag

    .Seeimagicalratio :2 ebelow.

    Iftherunnerisdividedtobranches,thetotalcrossseceb

  • CAEDSMouldDesign

    thecross

    esizeofthecasting.Smallcastingsrequirelargegatetoaltolargecastings.

    The ll runner ratiosare recommended in the referenceMikeWard:Gati CA,USA, 2006 although some references recommend largeratios:

    esmallratiosareduetothesizeofsprueornozzleopeningcrosssection;runnercrosssectionshouldbesmallerorequaltothesprueopening

    Magnesium:similartoaluminiumwithratiosfromthesmallerendand

    gthof thegate.Flowangleshouldbe1045 arenotpractical.Fan gate flow angle is the

    linedrawnbetweenthegatecornerandgatesideatofthetotal lengthofthegate.Thesmallertheflowanglethenarrowerandlongerthegate.Seeimagebelow

    andfansideatadistanceofofthetotalgatelength.

    rosssectionnlargementafterrossing(fanandngential)

    atetorunnertios(fan)

    Image20. Enlargetherunnercrosssectionby530%aftereachcrossing.Inthisexamplesectionisenlarged10%.

    HPDCrunnerandgatingsystemdesign13

    FangateFan gates can be constant in crosssectional area or converging. Constant crosssectionalareameansthatthegateareaissameastheopeningfromthemainrunner.In converginggate the crosssectional areaof thegate is smaller than theopeningfromthemainrunner.Asuitablegatetorunneropeningratiois1:1,01,5.Theratiodependsonalloytypeandthrunnerratiowheresmallerratiosaremorepractic

    fo owinggate tong Manual,NAD

    r

    Aluminium:1:1,11:1,4,flowangleshouldbebetween1035degreeswithratios1:1,3andlargerthan35degreeswithratio1:1,4

    Zinc:1:1,051:1,15,th

    higherrunnervelocities

    Flowanglesets limits to the total lendegrees.Over 45degrees flow anglesanglebetweenthecentrelineofthegateandastraight

    .

    Image21. Flowangle.Flowangleisananglebetweenthegatecenterlineandalinebetweengateopeningcorner

    Cecta

    Gra

    Flowangle(fan)

  • CAEDSMouldDesign

    A constant crosssectional area fan gatewidth grows according to the followingformula:

    lLhh

    h

    AW

    grg

    gatel

    +

    = , where

    Andaconvergingfangatewidthgrowsaccordingtotheformula:

    HPDCrunnerandgatingsystemdesign14

    ( )

    lLhh

    h

    LAcr

    AW

    grg

    gategate

    l

    +

    +

    =

    1

    ,where

    Wl=gatewidthatdistancelAgate=gatecrosssectionalarea

    gateheight

    These formulasdo if theheightof the runnergrows linearly.Presentday3DCADsystems areequ orsurfaceobjectbetwe t ingcurves. andmo weenthesetwo.(Image22.)

    offerapossibility toshape therunnerwithoutanyspecific formulas.Theyippedwithtoolswithwhichtheusercanshapeasolid

    en wodifferentshapeprofilesandguide the featurewithoneormoreguidThereisaneedtodimensionendprofileslikegateandrunnercrosssectiondelafeaturebet

    Image22. Shapingarunner SolidWorkstools.Intheleftimagethereisastraightfangate,whichisshapedwithtwop ofiles.Therightimagepresentsshapingrunnerwithendprofilesandaguidingcurve.Ifuserwantstobesureoftheshapeortheshapeshouldbemorecomplicated,itisrecommendedtou two eformulasbelow.

    withr

    semorethan profilesandcalculatetheshapewithth

    hg= hr=runnerheightL=fangatetotallengthl=distancefromthegate

    Wl=gatewidthatdistancelAgate=gatecrosssectionalareacr=convergeratio(1,051,4)hg=gateheighthr=runnerheightL=fangatetotallengthl=distancefromthegate

  • CAEDSMouldDesign

    Image23. Fangatedimensioningsymbols

    TangentialgateTangentialgate isnamedafter the converge fa towhich thegate is

    Thegatecrosssectionconvergestow erswithafactorofngent of the flow angle. The tangential run section is thegatearea,whichitfeedsdividedbytheflow leifthegateeight is 2mm and the runner feeds the last 10mmof thegate length, it is theneding20mm2crosssectionof the ingateand therunnerareashouldbe20mm2 /

    o2:1.Aspectratiosof1:1and3:1realsopossible.Thelargertheratiothewidertherunnerandthemoreheatislosttothemouldmaterial.Averagewidthisthewidthintherunnercentreline

    ctorsaccordingdesigned.ta

    ardsthegatebordner area for any cross

    in anglecosine.Forexamphfecos,whereistheflowangle.Flowangleisusuallysetbetween26and45.Othervaluesarepossible,butnotpractical.

    Thegaterunnerscrosssectionispresentedinthefollowingimage.Themaindimensions of the gate runner are: approach angle,draft angle, aspect ratio, height andaveragewidth.Aspect ratio is the averagewidth to theheightof thegate runner.Typicalapproachangleis30andtypicalaspectratia

    Image24. Tangentialgaterunnercrosssection.=draftinthebackface(80);=pproachangle.Aspectratioistheaveragewidthdividedbytheheightofthegaterunnerrofile.Averagewidthisthewidthatthemiddleoftheprofile.Runnercrosssectionenlargesithacoefficientofgatearea/cos,whereisaflowangle.

    apw

    HPDCrunnerandgatingsystemdesign15

  • CAEDSMouldDesign

    HPDCrunnerandgatingsystemdesign16

    The tapered cylindrical shapeprotrusion in the end of the gate runner is called ashock absorber. The function of a shock absorber is to prevent the castingmetalsplashing into the die cavity. It should be fedwith a tangential channel and thediametershouldbeapproximatelyasquarerootoftheingatearea6.

    Ifsowantedtherunnerandgatingdesignercan:

    dividetheingateintosegments,whicharefedfromonesinglegaterunner usemultipleingatestofeeddifferentsegmentsinacastingorfillfromdiffer

    entdirections;inthiscaseeachingateisfedwithaseparatega runner usemultipleingatesandcalculateflowanglesseparatelyforeachfeeding

    terun directthemetalflowfromtheingatebyshapingthegaterunner

    withtwobranchinggaterunners.

    ThemetalisdirectedwiththefollowingtechniquepresentedinMikeWard:GatingManual,NADCA,USA,2006.Theaimistoshapethefrontedgeofthegaterunnerwithcurvature,whichwillforcethemetaltoflowtoawanteddirection.

    Drawavectortothedirectionofthewantedmetalflow(1.).Thevectorshouldstartapproximatelyfromthegaterunnerfront.

    Drawavectorperpendiculartotheflowdirectionvector(2.). Drawavector,whichstartsfromthesamepointasthefirstvectorandwhich

    issettoanangleoftheselectedflowangle(3.).Payattentiontothemetalflowdirection.

    awaset

    keepingthecornerofthetwolastcreatedvectorsasacenterpoint(6.).

    te

    ga ner

    Image25. Segmentedanddirectedingate.Thesegmentedingateisfedfromtwosymmetricalgaterunners,whichmeetinthemainrunner.

    Image26. Multipleingatepositionsaroundthepart.Theingatescanbefedwithtwogaterunners,whichwillmeetatthemainrunnerasintheimagebelow.Theingatescanalsobefed

    Dr vector,whichisperpendiculartothelastdrawnvector(4.). Drawavectorfromtheendpointofthelastdrawnvectortothegateand

    thislineperpendiculartothegate(orvertical)(5.). Drawthegaterunnerfrontguidingcurvatureby

    6MikeWard:GatingManual,NADCA,USA,2006.p.56

  • CAEDSMouldDesign

    HPDCrunnerandgatingsystemdesign17

    1.) 2.)

    3.) 4.)

    5.) 6.)

    echnique.Image27. Metalflowdirectingt

    ld bewideenough.

    Gaterunnersmeetinthemainrunner.Themainrunnercrosssectionalareaislargerthanthecrosssectionalareainthegaterunner.Thecrosssectionalareashouldgrowequally towards themain runner and the approaching curvature shou

    (Seeimages.)

    Image28. Left:Approachcurvature.Right:Twomeetinggaterunners.

  • CAEDSMouldDesign

    HPDCrunnerandgatingsystemdesign18

    References

    Koskenniska,V. edit.Muotin suunnittelu javalmistus,Valimoinstituutti,Tampere,2004

    Orkas,edit.E.R.Keil:Painevalumuotinsuunnittelu,seminar20.22.10.1998,Espoo,Finland

    rd,M:GatingManual,NADCA,USA

    Wa ,2006

    /ColorImageDict > /JPEG2000ColorACSImageDict > /JPEG2000ColorImageDict > /AntiAliasGrayImages false /CropGrayImages true /GrayImageMinResolution 300 /GrayImageMinResolutionPolicy /OK /DownsampleGrayImages true /GrayImageDownsampleType /Bicubic /GrayImageResolution 300 /GrayImageDepth -1 /GrayImageMinDownsampleDepth 2 /GrayImageDownsampleThreshold 1.50000 /EncodeGrayImages true /GrayImageFilter /DCTEncode /AutoFilterGrayImages true /GrayImageAutoFilterStrategy /JPEG /GrayACSImageDict > /GrayImageDict > /JPEG2000GrayACSImageDict > /JPEG2000GrayImageDict > /AntiAliasMonoImages false /CropMonoImages true /MonoImageMinResolution 1200 /MonoImageMinResolutionPolicy /OK /DownsampleMonoImages true /MonoImageDownsampleType /Bicubic /MonoImageResolution 1200 /MonoImageDepth -1 /MonoImageDownsampleThreshold 1.50000 /EncodeMonoImages true /MonoImageFilter /CCITTFaxEncode /MonoImageDict > /AllowPSXObjects false /CheckCompliance [ /None ] /PDFX1aCheck false /PDFX3Check false /PDFXCompliantPDFOnly false /PDFXNoTrimBoxError true /PDFXTrimBoxToMediaBoxOffset [ 0.00000 0.00000 0.00000 0.00000 ] /PDFXSetBleedBoxToMediaBox true /PDFXBleedBoxToTrimBoxOffset [ 0.00000 0.00000 0.00000 0.00000 ] /PDFXOutputIntentProfile () /PDFXOutputConditionIdentifier () /PDFXOutputCondition () /PDFXRegistryName () /PDFXTrapped /False

    /Description > /Namespace [ (Adobe) (Common) (1.0) ] /OtherNamespaces [ > /FormElements false /GenerateStructure true /IncludeBookmarks false /IncludeHyperlinks false /IncludeInteractive false /IncludeLayers false /IncludeProfiles true /MultimediaHandling /UseObjectSettings /Namespace [ (Adobe) (CreativeSuite) (2.0) ] /PDFXOutputIntentProfileSelector /NA /PreserveEditing true /UntaggedCMYKHandling /LeaveUntagged /UntaggedRGBHandling /LeaveUntagged /UseDocumentBleed false >> ]>> setdistillerparams> setpagedevice