Download - Mould HPDC Runner
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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.
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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
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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.
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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.
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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
+=
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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
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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
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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.
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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.
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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.
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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
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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
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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
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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)
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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
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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
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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
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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.
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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
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