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外文翻译--一个典型的注塑模具设计指南 英文版.pdf

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外文翻译--一个典型的注塑模具设计指南 英文版.pdf

ATypicalInjectionMoldDesignGuideThischecklistcanbeusedasageneralreferenceguideforinjectionmolddesignengineers.Itisdividedinto3partsofamolddesignprocess.Part1RequirementstostartyourmolddesignChecktheinjectionmachinewherethemoldistobemounted.Thiswillhelpyoudecidethesizeandstructureofthemold.foreaseofinstallationandotherfactors.ImportantnotesLocatingringsizeorotherpositioningmethodNozzlesizeMethodofclampingAutoormanualTemperaturecontrolsystemDeterminethenumberofcavitiesandvolumerequirements.Thiswillhelpyoudecidethematerialthatyouaregoingtouseandothermoldcomponentsthatyouwillchooseforcosteffectivedesign.Determinethegatelocationandsize.Determinethelocationwhereejectorpinmarksareprohibited.Part2MoldbaselayoutPlacecavitiesclosetothecenterofthemoldtominimizebasesizeandrunnerlength.EnsurethatthemoldedpartremainsonthemovablehalfejectorhalfuponopeningofPLtofacilitateproperejection.Waterlinesshouldbeplacedasevenlyaspossibletothecontoursofthecavity.Usesupportpillarsunderneaththecavitypockets.Useejectorguidesformoldswithsmallejectorpinsandrectangularejectorpins.Provideeyeboltholeforeaseofmountinganddismounting.Installmoldopeningpreventionlocksontheoperatorside.Establishprybargrooveonthecornersofthemoldpartinglinetofacilitateeaseofmoldopeningduringassemblyandmaintenance.Bythistimeyoumayaskforthemoldlayoutapprovalfromthecustomer.Part3Cavity/coredetailsCheckmaterialshrinkage.Locateportionscornersforpossiblesignificantdeflectionanddeformation.Maintainuniformwallthickness.Draftangleshouldbewithindimensiontolerance.Dividecoreblockstosimplifymachiningandprovidegasventpath.Gate,smallcores,andcoreswithshutofffittingsarebetterdesignedasinsertablecomponentsforeasymodificationandrepair.Watchoutforpossibledeformationofcorepins.Positiontheejectorpinsontheribsandotherhighstrengthlocations.Ensureejectorbalance.Detailing/partdrawingIncludeallparametersneededforprocessingmaterial,quantity,surfacefinish/texture,dimensions,tolerancesandmanymore.Donotassumethemachinistunderstandseverything.Anydesignchangeandamendmentstothemoldmustbereapprovedbythecustomerormoldowner.Standardhorizontalclamppressesdelivermoltenresintothemoldthroughaholeinthecenterofthestationarypressplaten.Amaterialdeliverysystemusuallyconsistingofasprue,runners,andgatesthenleadstheresinthroughthemoldandintothecavity.Thesecomponentsofthematerialdeliverysystemarediscussedinthissection.SpruesThesprue,orientedparalleltothepressinjectionunit,deliversresintothedesireddepthintothemold,usuallythepartingline.Thoughtheycanbecutdirectlyintothemold,spruebushingsareusuallypurchasedasofftheshelfitemsandinsertedintothemoldseefigure718.Theheadendofthespruebushingcomespremachinedwithasphericalrecesstypically0.5or0.75inchradiustoreceiveandsealoffagainsttheroundedtipofthepressinjectionnozzle.Thespruebushingflowchanneldiametertypicallytaperslargertowardthepartinglineatarateof0.5inchperfoot.Thiseasesremovalofthemoldedsprue.Thesprueorificesize,thediameteratthesmallend,comesstandardinodd1/32sfrom5/32to11/32inch.Spruedesigncanaffectmoldingefficiencyandeaseofprocessing.Inmanymolds,thegreatestrestrictiontomaterialflowoccursatthepressnozzletipandsprueorifice.Theseareasseethehighestvolumetricflowrateoftheentiresystem.Anexcessivelysmallsprueorificecangeneratelargeamountsofmaterialshearandleadtomaterialdegradation,cosmeticproblems,andelevatedfillingpressure.Theproblemcanbeworseinthepressnozzletipbecausethetiporificemustbeslightlysmallerthanthesprueorificetoavoidforminganundercut.Thevolumetricflowrateusedduringfillinglargelydeterminesthecorrectsprueorificesize.Shotsizeandfillingspeed,aswellastheflowpropertiesofthespecificresin,governtherequiredflowrate.Largepartsand/orpartsneedingfastfillingspeedsrequirelargesprueorificediameterstoavoidproblemsassociatedwithexcessiveflowshear.Asageneralrule,amorphousresinsandblendssuchasMakrolonpolycarbonate,LustranABS,andBayblendPC/ABSresinsrequirelargerspruesandrunnersthansemicrystallineresinssuchasDurethanPA6andPocanPBT.Thediameteratthebaseofthesprueincreaseswithincreasingspruelength.Standardspruetaper,typicallyonehalfinchperfoot,leadstolargebasediametersinlongsprues.Thislargebasediameterlengthenscoolingandcycletimesandalsoleadstoregrindproblems.Figure719showstypicalspruesizesforBayeramorphousresinsasafunctionofshotsizeandfillingtime.Becausethemaximumshearrateinasprueoccursattheorificeandthemajorityofshearheatingandpressurelosstakesplaceinthefirsttwoinches,theseguidelinesshouldapplytospruesofvariouslengths.Partgeometryinfluencesfillingtimetosomeextent.Forexample,partswithamixofthickandthinfeaturesmayneedafastfillingspeedtopreventprematurecoolingofthethinfeatures.Othergeometriesmayrequireslowerfillingspeedstopreventproblemssuchascosmeticdefectsorexcessiveclamptonnagerequirements.Hotspruebushingsprovideonesolutiontothisproblem.Hotspruebushingshaveaheatedflowchannelthattransportsmaterialalongitslengthinmoltenform,eliminatingorshorteningthemoldedcoldsprue.Additionally,somemoldsrelyonextensionpressnozzlesthatreachdeepintothemoldtoreducespruelength.RunnersUnlikesprues,whichdelivermaterialdepthwisethroughthecenterofthemoldplates,runnerstypicallytransportmaterialthroughchannelsmachinedintothepartingline.Runnerdesigninfluencespartqualityandmoldingefficiency.Overlythickrunnerscanlengthencycletimeneedlesslyandincreasecostsassociatedwithregrind.Conversely,thinrunnerscancauseexcessivefillingpressuresandrelatedprocessingproblems.Theoptimumrunnerdesignrequiresabalancebetweeneaseoffilling,molddesignfeasibility,andrunnervolume.Materialpassingthroughtherunnerduringmoldfillingformsafrozenwalllayerasthemoldsteeldrawsheatfromthemelt.Thislayerrestrictstheflowchannelandincreasesthepressuredropthroughtherunner.Roundcrosssectionrunnersminimizecontactwiththemoldsurfaceandgeneratethesmallestpercentageoffrozenlayercrosssectionalarea.Asrunnerdesignsdeviatefromround,theybecomelessefficientseefigure720.Roundrunnersrequiremachininginbothhalvesofthemold,increasingthepotentialformismatchandflowrestriction.Agoodalternative,theroundbottomedtrapezoid,requiresmachininginjustonemoldhalf.Essentiallyaroundcrosssectionwithsidestaperedbyfivedegreesforejection,thisdesignisnearlyasefficientasthefullrounddesign.Therunnersystemoftenaccountsformorethan40ofthepressurerequiredtofillthemold.Becausemuchofthispressuredropcanbeattributedtorunnerlength,optimizetheroutetoeachgatetominimizerunnerlength.Forexample,replacecorneredpathswithdiagonalsorreorientthecavitytoshortentherunner.

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