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外文资料--A technical note on the characterization of electroformed.pdf

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外文资料--A technical note on the characterization of electroformed.pdf

JournalofMaterialsProcessingTechnology1762006273–277AbstractprocedurethemetallographicwithK1.industrywiththisitidoubtablethetointhetheaityfield,theturingcomposedusinTheir0924-0136/doiAtechnicalnoteonthecharacterizationofelectroformednickelshellsfortheirapplicationtoinjectionmoldsMarioD.Monzon,M.DoloresMarrero,A.NizardoBenitez,PedroM.Hernandez,J.FranciscoCardenesUniversidaddeLasPalmasdeGranCanaria,DepartamentodeIngenieriaMecanica,SpainReceived19November2003;receivedinrevisedform14January2006;accepted11April2006Thetechniquesofrapidprototypingandrapidtoolinghavebeenwidelydevelopedduringthelastyears.Inthisarticle,electroformingasatomakecoresforplasticsinjectionmoldsisanalysed.ShellsareobtainedfrommodelsmanufacturedthroughrapidprototypingusingFDMsystem.Themainobjectiveistoanalyzethemechanicalfeaturesofelectroformednickelshells,studyingdifferentaspectsrelatedtotheirstructure,hardness,internalstressesandpossiblefailures,byrelatingthesefeaturestotheparametersofproductionoftheshellsanelectroformingequipment.Finallyacorewastestedinaninjectionmold.2006ElsevierB.V.Allrightsreserved.eywordsElectroplating;Electroforming;Microstructure;NickelIntroductionOneofthemostimportantchallengeswithwhichmoderncomesacrossistooffertheconsumerbetterproductsplasticinjectedpieces[1–3],however,itistruethatitiswheretheyhavedevelopedmoreandwheretheyfindthehighestoutput.Thispaperisincludedwithinawiderresearchlinewhereitoutstandingvarietyandtimevariabilitynewdesigns.Forreason,modernindustrymustbemoreandmorecompet-veandithastoproducewithacceptablecosts.Thereisnothatcombiningthetimevariableandthequalityvari-isnoteasybecausetheyfrequentlyconditiononeanother;technologicaladvancesintheproductivesystemsaregoingpermitthatcombinationtobemoreefficientandfeasibleawaythat,forexample,ifitisobservedtheevolutionofsystemsandtechniquesofplasticsinjection,wearriveatconclusionthat,infact,ittakeslessandlesstimetoputnewproductonthemarketandwithhigherlevelsofqual-.Themanufacturingtechnologyofrapidtoolingis,inthisoneofthosetechnologicaladvancesthatmakespossibleimprovementsintheprocessesofdesigningandmanufac-injectedparts.Rapidtoolingtechniquesarebasicallyofacollectionofproceduresthataregoingtoallowtoobtainamoldofplasticparts,insmallormediumseries,ashortperiodoftimeandwithacceptableaccuracylevels.applicationisnotonlyincludedinthefieldofmakingE-mailaddressmmonzondim.ulpgc.esM.D.Monzon.attemptstrialstartinganequipment.formingcationswparametersrapidratemethod.2.throughepoxiccoreing–seefrontmatter2006ElsevierB.V.Allrightsreserved.10.1016/j.jmatprotec.2006.04.003tostudy,define,analyze,testandpropose,atanindus-level,thepossibilityofcreatingcoresforinjectionmoldsfromobtainingelectroformednickelshells,takingasinitialmodelaprototypemadeinaFDMrapidprototypingItalsowouldhavetosaybeforehandthattheelectro-techniqueisnotsomethingnewbecauseitsappli-intheindustryarecountless[3],butthisresearchorkhastriedtoinvestigatetowhatextentandunderwhichtheuseofthistechniqueintheproductionofmoldsistechnicallyfeasible.Allmadeinanaccu-andsystematizedwayofuseandproposingaworkingManufacturingprocessofaninjectionmoldThecoreisformedbyathinnickelshellthatisobtainedtheelectroformingprocess,andthatisfilledwithanresinwithmetallicchargeduringtheintegrationintheplate[4]ThismoldFig.1permitsthedirectmanufactur-byinjectionofatypeamultipleusespecimen,astheyare274Processingdefinedspecimentionandtools.researchedabcdeTheformedplaten.processca3.whichwhenbathanmadethethecathodesulf10703tomolds,sulfstressesconditions,aroundalsoisamidealsopermittingoftoharmfultidistribhasM.D.Monzonetal./JournalofMaterialsFig.1.Manufacturedinjectionmoldwithelectroformedcore.bytheUNE-ENISO3167standard.Thepurposeofthisistodeterminethemechanicalpropertiesofacollec-ofmaterialsrepresentativeindustry,injectedinthesetoolsitscoMParisonwiththepropertiesobtainedbyconventionalThestagestoobtainacore[4],accordingtothemethodologyinthiswork,arethefollowingDesigninCADsystemofthedesiredobject.ModelmanufacturinginarapidprototypingequipmentFDMsystem.ThematerialusedwillbeanABSplastic.Manufacturingofanickelelectroformedshellstartingfromthepreviousmodelthathasbeencoatedwithaconductivepaintbeforehanditmusthaveelectricalconductivity.Removaloftheshellfromthemodel.Productionofthecorebyfillingthebackoftheshellwithepoxyresinresistanttohightemperaturesandwiththerefrigeratingductsmadewithcoppertubes.injectionmoldhadtwocavities,oneofthemwastheelectro-coreandtheotherwasdirectlymachinedinthemovingThus,itwasobtained,withthesametoolandinthesameconditions,toinjectsimultaneouslytwospecimensinvitiesmanufacturedwithdifferenttechnologies.ObtaininganelectroformedshelltheequipmentElectrodeposition[5,6]isanelectrochemicalprocessinachemicalchangehasitsoriginwithinanelectrolytepassinganelectriccurrentthroughit.Theelectrolyticisformedbymetalsaltswithtwosubmergedelectrodes,anodenickelandacathodemodel,throughwhichitistopassanintensitycomingfromaDCcurrent.Whencurrentflowsthroughthecircuit,themetalionspresentinsolutionaretransformedintoatomsthataresettledonthecreatingamoreorlessuniformdepositlayer.Theplatingbathusedinthisworkisformedbynickelamate[7,8]ataconcentrationof400ml/l,nickelchlorideg/l,boricacid50g/l,AllbriteSLA30cc/landAllbrite2cc/l.Theselectionofthiscompositionismainlyduethetypeofapplicationweintend,thatistosay,injectionevenwhentheinjectionismadewithfibreglass.Nickelamateallowsustoobtainanacceptablelevelofinternalhahatemperatureifying4.testsformedFig.vfromofperature560conoperateTechnology1762006273–277intheshellthetestsgaveresults,fordifferentprocessnotsuperiorto50MPaandforoptimumconditions2MPa.Nevertheless,suchlevelofinternalpressureisaconsequenceofusingasanadditiveAllbriteSLA,whichastressreducerconstitutedbyderivativesoftoluenesulfon-andbyformaldehydeinaqueoussolution.Suchadditivefavourstheincreaseoftheresistanceoftheshellwhenasmallergrain.Allbrite703isanaqueoussolutionbiodegradablesurface-actingagentsthathasbeenutilizedreducetheriskofpitting.Nickelchloride,inspiteofbeingfortheinternalstresses,isaddedtoenhancetheconduc-vityofthesolutionandtofavourtheuniformityinthemetallicutioninthecathode.TheboricacidactsasapHbuffer.TheequipmentusedtomanufacturethenickelshellstestedbeenasfollowsPolypropylenetank600mm400mm500mminsize.Threeteflonresistors,eachonewith800W.Mechanicalstirringsystemofthecathode.Systemforrecirculationandfiltrationofthebathformedbyapumpandapolypropylenefilter.Chargingrectifier.Maximumintensityincontinuous50Aandcontinuouscurrentvoltagebetween0and16V.TitaniumbasketwithnickelanodesIncoS-RoundsElec-trolyticNickelwithapurityof99.Gasesaspirationsystem.Oncethebathhasbeendefined,theoperativeparametersthatvebeenalteredfortestingdifferentconditionsoftheprocess2vebeenthecurrentdensitybetween1and22A/dm,thebetween35and55◦CandthepH,partiallymod-thebathcomposition.ObtainedhardnessOneofthemostinterestingconclusionsobtainedduringthehasbeenthatthelevelofhardnessofthedifferentelectro-shellshasremainedatratherhighandstablevalues.In2,itcanbeobservedthewayinwhichforcurrentdensityaluesbetween2.5and22A/dm2,thehardnessvaluesrange540and580HV,atpH40.2andwithatemperature45◦C.IfthepHofthebathisreducedat3.5andthetem-is55◦Cthosevaluesareabove520HVandbelowHV.Thisfeaturemakesthetestedbathdifferentfromotherventionalonescomposedbynickelsulfamate,allowingtowithawiderrangeofvalues;nevertheless,suchopera-Fig.2.Hardnessvariationwithcurrentdensity.pH40.2,T45◦C.ProcessingTechnology1762006273–277275tistresstainhand,200–250isthemoststeel520–595anickmaterialsoffillingforplasticsshellminimumpitting.5.currentplesperpendicularpreparation,ishedacid15,observPME3-ADLarticle,thethelayerapproximatelyzontalThus,thegoingthebemoldsTTSeries1234Fig.3.Series1150,etch1.Fig.4.Series2300,etch2.M.D.Monzonetal./JournalofMaterialsvitywillbelimiteddependingonotherfactors,suchasinternalbecauseitsvariabilitymayconditiontheworkatcer-valuesofpH,currentdensityortemperature.OntheotherthehardnessofaconventionalsulfamatebathisbetweenHV,muchlowerthantheoneobtainedinthetests.Itnecessarytotakeintoaccountthat,foraninjectionmold,hardnessisacceptablestartingfrom300HV.Amongtheusualmaterialsforinjectionmoldsitispossibletofindforimprovement290HV,steelforintegralhardeningHV,casehardenedsteel760–800HV,etc.,insuchwaythatitcanbeobservedthatthehardnesslevelsoftheelshellswouldbewithinthemedium–highrangeoftheforinjectionmolds.Theobjectiontothelowductilitytheshelliscompensatedinsuchawaywiththeepoxyresinthatwouldfollowitbecausethisistheoneresponsibleholdinginwardlythepressurechargesoftheprocessesofinjection;thisisthereasonwhyitisnecessaryforthetohaveathicknessashomogeneousaspossibleaboveavalueandwithabsenceofimportantfailuressuchasMetallographicstructureInordertoanalyzethemetallographicstructure,thevaluesofdensityandtemperatureweremainlymodified.Thesam-wereanalyzedinfrontalsectionandintransversalsectiontothedeposition.Forachievingaconvenienttheywereconvenientlyencapsulatedinresin,pol-andetchedindifferentstageswithamixtureofaceticandnitricacid.Theetchesarecarriedoutatintervalsof25,40and50s,afterbeingpolishedagain,inordertobeedafterwardsinametallographicmicroscopeOlympus3.3/10.BeforegoingontocommentthephotographsshowninthisitisnecessarytosaythatthemodelsusedtomanufactureshellsweremadeinaFDMrapidprototypingmachinewheremoltenplasticmaterialABS,thatlatersolidifies,issettledbylayer.Ineachlayer,theextruderdieleavesathread0.15mmindiameterwhichiscompactedhori-andverticallywiththethreadsettledinmediatelyafter.inthesurfaceitcanbeobservedthinlinesthatindicateroadsfollowedbytheheadofthemachine.Theselinesaretoactasareferencetoindicatethereproducibilitylevelofnickelsettled.Thereproducibilityofthemodelisgoingtoafundamentalelementtoevaluateabasicaspectofinjectionthesurfacetexture.ThetestedseriesareindicatedinTable1.able1estedseriespHTemperature◦CCurrentdensityA/dm24.20.2552.223.90.2455.564.00.24510.004.00.24522.22firstthatstillalessetchisdarkconditionsFig.3illustratesthesurfaceofasampleoftheseriesaftertheetch.ItshowstheroadsoriginatedbytheFDMmachine,istosaythatthereisagoodreproducibility.Itcannotbenoticedtheroundedgrainstructure.InFig.4,series2,aftersecondetch,itcanbeobservedalineoftheroadinawayclearthaninthepreviouscase.InFig.5,series3and2◦itbeginstoappeartheroundedgrainstructurealthoughitverydifficulttochecktheroadsatthistime.Besides,themostenedareasindicatethepresenceofpittingbyinadequateofprocessandbathcomposition.Fig.5.Series3300,etch2.276Processingandmodelfordeposition,ditionswhatalthoughabosulfnon-laminarvturetheSLA.turecurrent6.applicationDiftiestensiometerwithwidthonlysilestresses.nickintestedforacceptableistionsstresses.M.D.Monzonetal./JournalofMaterialsFig.6.Planetransversalofseries2600,etch2.Thisbehaviorindicatesthat,workingatalowcurrentdensityahightemperature,shellswithagoodreproducibilityoftheandwithasmallgrainsizeareobtained,thatis,adequatetherequiredapplication.Iftheanalysisiscarriedoutinaplanetransversaltotheitcanbetestedinallthesamplesandforallthecon-thatthegrowthstructureofthedepositislaminarFig.6,isverysatisfactorytoobtainahighmechanicalresistanceattheexpenseofalowductibility.Thisqualityisdue,veall,tothepresenceoftheadditivesusedbecauseanickelamatebathwithoutadditivesnormallycreatesafibrousandstructure[9].Themodificationuntilanearlynullalueofthewettingagentgaveasaresultthatthelaminarstruc-wasmaintainedinanycase,thatmatterdemonstratedthatdeterminantforsuchstructurewasthestressreducerAllbriteOntheotherhand,itwasalsotestedthatthelaminarstruc-variesaccordingtothethicknessofthelayerintermsofthedensity.InternalstressesOneofthemaincharacteristicthatashellshouldhaveforitslikeaninsertistohavealowlevelofinternalstresses.ferenttestsatdifferentbathtemperaturesandcurrentdensi-weredoneandameasuresystemrestedoncathodeflexuralmethodwasused.Asteeltestingcontrolwasusedasidefixedandtheotherfree160mmlength,12.7mmandthickness0.3mm.Becausethemetallicdepositionisinonesidethetestingcontrolhasamechanicalstrainten-orcompressivestressthatallowstocalculatetheinternalStoneymodel[10]wasappliedandwassupposedthatelsubstratumthicknessisenoughsmall3H9262mtoinfluence,anelasticpointofview,tothestrainedsteelpart.Inallthecasesthemostvalueofinternalstresswasunder50MPaextremeconditionsand2MPaforoptimalconditions,anvaluefortherequiredapplication.Theconclusionthattheelectroliticbathallowstoworkatdifferentcondi-andparameterswithoutasignificantvariationofinternal7.moplastichasdimensions,calbycore,betweenthematerials.itofenceecrystallinenoticedcore,around8.checkhasertiesthatgoodstructure.becoreplasticReferTechnology1762006273–277Fig.7.Analysisbyphotoelasticityofinjectedspecimens.TestoftheinjectionmoldTestshavebeencarriedoutwithvariousrepresentativether-materialssuchasPP,PA,HDPEandPC,anditbeenanalysedthepropertiesoftheinjectedpartssuchasweight,resistance,rigidityandductility.Mechani-propertiesweretestedbytensiledestructivetestsandanalysisphotoelasticity.About500injectionswerecarriedoutonthisremainingunderconditionsofwithstandingmanymore.Ingeneralterms,importantdifferenceswerenotnoticedthebehaviorofthespecimensobtainedinthecoreandonesfromthemachinedcavity,forthesetoftheanalysedHoweverintheanalysisbyphotoelasticiyFig.7wasnoticedadifferenttensionalstatebetweenbothtypesspecimens,basicallyduetodifferencesintheheattransfer-andrigidityoftherespectivemoldcavities.ThisdifferencexplainstheductilityvariationsmoreoutstandinginthepartiallymaterialssuchasHDPEandPA6.ForthecaseofHDPEinalltheanalysedtestedtubesitwasalowerductilityinthespecimensobtainedinthenickelquantifiedabout30.InthecaseofPA6thisvaluewas50.ConclusionsAfterconsecutivetestsandindifferentconditionsithasbeenedthatthenickelsulfamatebath,withtheutilizedadditivesallowedtoobtainnickelshellswithsomemechanicalprop-acceptablefortherequiredapplication,injectionmolds,istosay,goodreproducibility,highlevelofhardnessandmechanicalresistanceintermsoftheresultantlaminarThemechanicaldeficienciesofthenickelshellwillpartiallyreplacedbytheepoxyresinthatfinishesshapingthefortheinjectionmold,allowingtoinjectmediumseriesofpartswithacceptablequalitylevels.ences[1]A.E.W.Rennie,C.E.Bocking,G.R.Bennet,Electroformingofrapidpro-totypingmandrelsforelectrodischargemachiningelectrodes,J.Mater.Process.Technol.1102001186–196.[2]P.K.D.V.Yarlagadda,I.P.Ilyas,P.Chrstodoulou,Developmentofrapidtoolingforsheetmetaldrawingusingnickelelectroformingandstereolithographyprocesses,J.Mater.Process.Technol.1112001286–294.

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