注塑成型优化方法有出处中英文翻译.docx

注塑成型优化方法有出处中英文翻译.docx

《注塑成型优化方法有出处中英文翻译.docx》由会员分享，可在线阅读，更多相关《注塑成型优化方法有出处中英文翻译.docx（15页珍藏版）》请在冰点文库上搜索。

注塑成型优化方法有出处中英文翻译

Atechnicalnoteonthecharacterizationofelectroformednickelshellsfortheirapplicationtoinjectionmolds

——UniversidaddeLasPalmasdeGranCanaria,DepartamentodeIngenieriaMecanica,Spain

Abstract

Thetechniquesofrapidprototypingandrapidtoolinghavebeenwidelydevelopedduringthelastyears.Inthisarticle,electroformingasaproceduretomakecoresforplasticsinjectionmoldsisanalysed.ShellsareobtainedfrommodelsmanufacturedthroughrapidprototypingusingtheFDMsystem.Themainobjectiveistoanalyzethemechanicalfeaturesofelectroformednickelshells,studyingdifferentaspectsrelatedtotheirmetallographicstructure,hardness,internalstressesandpossiblefailures,byrelatingthesefeaturestotheparametersofproductionoftheshellswithanelectroformingequipment.Finallyacorewastestedinaninjectionmold.

Keywords:

Electroplating;Electroforming;Microstructure;Nickel

ArticleOutline

1.Introduction

2.Manufacturingprocessofaninjectionmold

3.Obtaininganelectroformedshell:

theequipment

4.Obtainedhardness

5.Metallographicstructure

6.Internalstresses

7.Testoftheinjectionmold

8.Conclusions

References

1.Introduction

Oneofthemostimportantchallengeswithwhichmodernindustrycomesacrossistooffertheconsumerbetterproductswithoutstandingvarietyandtimevariability（newdesigns）.Forthisreason,modernindustrymustbemoreandmorecompetitiveandithastoproducewithacceptablecosts.Thereisnodoubtthatcombiningthetimevariableandthequalityvariableisnoteasybecausetheyfrequentlyconditiononeanother;thetechnologicaladvancesintheproductivesystemsaregoingtopermitthatcombinationtobemoreefficientandfeasibleinawaythat,forexample,ifitisobservedtheevolutionofthesystemsandtechniquesofplasticsinjection,wearriveattheconclusionthat,infact,ittakeslessandlesstimetoputanewproductonthemarketandwithhigherlevelsofquality.Themanufacturingtechnologyofrapidtoolingis,inthisfield,oneofthosetechnologicaladvancesthatmakespossibletheimprovementsintheprocessesofdesigningandmanufacturinginjectedparts.Rapidtoolingtechniquesarebasicallycomposedofacollectionofproceduresthataregoingtoallowustoobtainamoldofplasticparts,insmallormediumseries,inashortperiodoftimeandwithacceptableaccuracylevels.Theirapplicationisnotonlyincludedinthefieldofmakingplasticinjectedpieces[1],[2]and[3],however,itistruethatitiswheretheyhavedevelopedmoreandwheretheyfindthehighestoutput.

Thispaperisincludedwithinawiderresearchlinewhereitattemptstostudy,define,analyze,testandpropose,atanindustriallevel,thepossibilityofcreatingcoresforinjectionmoldsstartingfromobtainingelectroformednickelshells,takingasaninitialmodelaprototypemadeinaFDMrapidprototypingequipment.

Italsowouldhavetosaybeforehandthattheelectroformingtechniqueisnotsomethingnewbecauseitsapplicationsintheindustryarecountless[3],butthisresearchworkhastriedtoinvestigatetowhatextentandunderwhichparameterstheuseofthistechniqueintheproductionofrapidmoldsistechnicallyfeasible.Allmadeinanaccurateandsystematizedwayofuseandproposingaworkingmethod.

2.Manufacturingprocessofaninjectionmold

Thecoreisformedbyathinnickelshellthatisobtainedthroughtheelectroformingprocess,andthatisfilledwithanepoxicresinwithmetallicchargeduringtheintegrationinthecoreplate[4]Thismold（Fig.1）permitsthedirectmanufacturingbyinjectionofatypeamultipleusespecimen,astheyaredefinedbytheUNE-ENISO3167standard.Thepurposeofthisspecimenistodeterminethemechanicalpropertiesofacollectionofmaterialsrepresentativeindustry,injectedinthesetoolsanditscoMParisonwiththepropertiesobtainedbyconventionaltools.

Thestagestoobtainacore[4],accordingtothemethodologyresearchedinthiswork,arethefollowing:

（a）DesigninCADsystemofthedesiredobject.

（b）Modelmanufacturinginarapidprototypingequipment（FDMsystem）.ThematerialusedwillbeanABSplastic.

（c）Manufacturingofanickelelectroformedshellstartingfromthepreviousmodelthathasbeencoatedwithaconductivepaintbeforehand（itmusthaveelectricalconductivity）.

（d）Removaloftheshellfromthemodel.

（e）Productionofthecorebyfillingthebackoftheshellwithepoxyresinresistanttohightemperaturesandwiththerefrigeratingductsmadewithcoppertubes.

Theinjectionmoldhadtwocavities,oneofthemwastheelectroformedcoreandtheotherwasdirectlymachinedinthemovingplaten.Thus,itwasobtained,withthesametoolandinthesameprocessconditions,toinjectsimultaneouslytwospecimensincavitiesmanufacturedwithdifferenttechnologies.

3.Obtaininganelectroformedshell:

theequipment

Electrodeposition[5]and[6]isanelectrochemicalprocessinwhichachemicalchangehasitsoriginwithinanelectrolytewhenpassinganelectriccurrentthroughit.Theelectrolyticbathisformedbymetalsaltswithtwosubmergedelectrodes,ananode（nickel）andacathode（model）,throughwhichitismadetopassanintensitycomingfromaDCcurrent.Whenthecurrentflowsthroughthecircuit,themetalionspresentinthesolutionaretransformedintoatomsthataresettledonthecathodecreatingamoreorlessuniformdepositlayer.

Theplatingbathusedinthisworkisformedbynickelsulfamate[7]and[8]ataconcentrationof400 ml/l,nickelchloride（10 g/l）,boricacid（50 g/l）,AllbriteSLA（30 cc/l）andAllbrite703（2 cc/l）.Theselectionofthiscompositionismainlyduetothetypeofapplicationweintend,thatistosay,injectionmolds,evenwhentheinjectionismadewithfibreglass.Nickelsulfamateallowsustoobtainanacceptablelevelofinternalstressesintheshell（thetestsgaveresults,fordifferentprocessconditions,notsuperiorto50 MPaandforoptimumconditionsaround2 MPa）.Nevertheless,suchlevelofinternalpressureisalsoaconsequenceofusingasanadditiveAllbriteSLA,whichisastressreducerconstitutedbyderivativesoftoluenesulfonamideandbyformaldehydeinaqueoussolution.Suchadditivealsofavourstheincreaseoftheresistanceoftheshellwhenpermittingasmallergrain.Allbrite703isanaqueoussolutionofbiodegradablesurface-actingagentsthathasbeenutilizedtoreducetheriskofpitting.Nickelchloride,inspiteofbeingharmfulfortheinternalstresses,isaddedtoenhancetheconductivityofthesolutionandtofavourtheuniformityinthemetallicdistributioninthecathode.TheboricacidactsasapHbuffer.

Theequipmentusedtomanufacturethenickelshellstestedhasbeenasfollows:

•Polypropylenetank:

600 mm × 400 mm × 500 mminsize.

•Threeteflonresistors,eachonewith800 W.

•Mechanicalstirringsystemofthecathode.

•Systemforrecirculationandfiltrationofthebathformedbyapumpandapolypropylenefilter.

•Chargingrectifier.Maximumintensityincontinuous50 Aandcontinuouscurrentvoltagebetween0and16 V.

•Titaniumbasketwithnickelanodes（IncoS-RoundsElectrolyticNickel）withapurityof99%.

•Gasesaspirationsystem.

Oncethebathhasbeendefined,theoperativeparametersthathavebeenalteredfortestingdifferentconditionsoftheprocesshavebeenthecurrentdensity（between1and22 A/dm2）,thetemperature（between35and55 °C）andthepH,partiallymodifyingthebathcomposition.

4.Obtainedhardness

Oneofthemostinterestingconclusionsobtainedduringthetestshasbeenthatthelevelofhardnessofthedifferentelectroformedshellshasremainedatratherhighandstablevalues.InFig.2,itcanbeobservedthewayinwhichforcurrentdensityvaluesbetween2.5and22 A/dm2,thehardnessvaluesrangefrom540and580 HV,atpH4 ± 0.2andwithatemperatureof45 °C.IfthepHofthebathisreducedat3.5andthetemperatureis55 °Cthosevaluesareabove520 HVandbelow560 HV.Thisfeaturemakesthetestedbathdifferentfromotherconventionalonescomposedbynickelsulfamate,allowingtooperatewithawiderrangeofvalues;nevertheless,suchoperativitywillbelimiteddependingonotherfactors,suchasinternalstressbecauseitsvariabilitymayconditiontheworkatcertainvaluesofpH,currentdensityortemperature.Ontheotherhand,thehardnessofaconventionalsulfamatebathisbetween200–250 HV,muchlowerthantheoneobtainedinthetests.Itisnecessarytotakeintoaccountthat,foraninjectionmold,thehardnessisacceptablestartingfrom300 HV.Amongthemostusualmaterialsforinjectionmoldsitispossibletofindsteelforimprovement（290 HV）,steelforintegralhardening（520–595 HV）,casehardenedsteel（760–800 HV）,etc.,insuchawaythatitcanbeobservedthatthehardnesslevelsofthenickelshellswouldbewithinthemedium–highrangeofthematerialsforinjectionmolds.Theobjectiontothelowductilityoftheshelliscompensatedinsuchawaywiththeepoxyresinfillingthatwouldfollowitbecausethisistheoneresponsibleforholdinginwardlythepressurechargesoftheprocessesofplasticsinjection;thisisthereasonwhyitisnecessaryfortheshelltohaveathicknessashomogeneousaspossible（aboveaminimumvalue）andwithabsenceofimportantfailuressuchaspitting.

5.Metallographicstructure

Inordertoanalyzethemetallographicstructure,thevaluesofcurrentdensityandtemperatureweremainlymodified.Thesampleswereanalyzedinfrontalsectionandintransversalsection（perpendiculartothedeposition）.Forachievingaconvenientpreparation,theywereconvenientlyencapsulatedinre