3D打印英文文献 翻译.docx

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1、JournaloftheEuropeanCeramicSociety31(2011)2543-2550Inkjetprintingceramics:FromdropstosolidB.DerbySchoolofMaterials,UniversityofManchester,OxfordRoad,ManchesterM139P1.,UKAvailableonline16February2011AbstractInkjetprintingisapowerfulInicrofabricationtoolthathasbeenappliedtothemanufactureofceramiccompo

2、nents.Tosuccessfullyfabricateceramicobjectsanumberofconditionsmustbesatisfiedconcerningfluidpropertiesanddropplacementaccuracy.Ithasbeenproposedthatfluidsareprintablewithinthebounds1Z2forstabledropgeneration.19Reisextendedthisthroughnumericalsimulationandproposedthefollowingrange,10Z1,forstabledropf

3、ormation.20IfZ10,dropletsareaccompaniedbyunwantedsatellitedrops.Jangetal.studiedtheDODprintabilityofanumberoffluidmixturesofethanol,waterandethyleneglycol.ThroughthistheyexploredarangeofvaluesofOhanddeterminedthattherangeofprintabilitywasFig. 1. Fromm,sparameterZ(Z=1/Oh)influencestheprintabilityoffl

4、uids.DashedlinesidentifythelimitsforprintabilityproposedbyReisetal.20Experi-mentalpointsareplottedforanumberofceramicsuspensions/inks:greysymbolsindicatesuccessfulinkjetprinting,blacksymbolsindicatethatnodropswereformed,andwhitesymbolsindicatethepresenceofsatellitedropsalongwiththemainprinteddrop.4Z

5、Z1(whereZ=lOh)canbeusedasaguidetothedevelopmentoffluidsforinkjetprinting.ThesuitabilityofafluidforinkjetprintingcanberoughlyassessedbyitsOhnesorgenumber.Howeverthereareotherlim-itsoffluidbehaviourthatimposeadditionallimitstopracticaldropgeneration.Inordertogenerateasmallradiusdrop,thesur-facetension

6、andassociated1.aplacepressuremustbeovercomebeforeadropcanbeejectedfromaprinter.DuineveldproposedthatthiscanbedescribedbyaminimumvalueoftheWebernumber,We4,belowwhichthereisinsufficientfluidflowtoovercomesurfacetension.24Afinalboundtoprintabilityisgivenbytheonsetofsplashingthatoccursifadrophitsthesubs

7、tratewithvelocityaboveacriticalthreshold.FromtheworkofStoweandHadfield,25thisoccurswhenWel2Rel450.Theselimit-ingboundsdefinearegionoftheparameterspaceofWeandRe,withinwhichDODinkjetprintingispossible.5,6Fig.2showsFig. 2. Inkjetprintingispracticalforalimitedrangeoffluidsandprintingcon-ditions.Thisisil

8、lustratedhereinaparameterspacedefinedbyaxesofReynoldsandWebernumbers.BasedonadiagramoriginallypublishedinRef.5.thisparameterspaceandtheregionsuitableforDODinkjetprinting.Dropvelocityincreasesdiagonally,asindicatedandhaslowerandupperboundsthataredefinedbytheappropriatelimitsofdropejectionandsplashing

9、,orthogonaltovelocityistheOhnesorgenumber;whichdefinesthelimitsofthefluidprop-erties,thusFig.2canbeconsideredrepresentingaguidetothelimitsofbothfluidcharacteristicsanddropdynamicsconsistentwiththepracticaluseofpiezoelectricDODinkjetprinting.3. Dropimpact,spreadingandcoalescenceAsdiscussedearlier,ani

10、mportantaspectofinkjetprintinginmanufacturingtechnologyistheprocessbywhichadjacentdropsinteracttoformasolid.Inallcasestheliquiddropwillinteractwithasolidsubstrate.Followingdepositiontherewillbeaperiodwhenthedrop,sshapeiscontrolledbyfluidpro-cessespriortosolidification.Thusanimportantconsiderationist

11、heappropriatetimeconstantsthatapplytothemechanismsofsurfacespreadingandsolidication.Hereweareconfiningourdiscussiontosolidificationthroughevaporation.Giventhatdropletsolidificationtimescalesarenormallyintheregimeofaround1sanddropletdepositionratesare1kHz,weneedtoconsidertheinteractionbetweenmanyliqu

12、iddropletsonthesurfaceofthesubstrate.Itispossibletouseinterlacingandsequentialprintingpassestodepositisolateddrops,allowthemtosolidifyandthenfillinthegapstoproduceaprintedplane.However,thismethodologyproducesanirregulardepositwithpoorsurfaceroughnessforeachprintedlaye9withaconse-quentriskofdefectsfr

13、ompoorpenetrationoftheliquid.Ifprintingoccurswithappropriatedropspacingtoallowover-lapbeforesolidication,theinteractionbetweenadjacentliquiddropsandtheconsequentinfluenceofsurfacetensionwilltendtoproducesmoothsurfacesandeliminatepossibledefectsbetweensolidifieddrops.Whenaliquiddropimpactsaplanarsubs

14、trateitwilldeformandspreadtocoverthesubstrate,ultimatelyachievinganequi-Iibriumsessiledropconfiguration.YarinhasrecentlyreviewedtheimpactofdropsoverasizeandvelocityrangethatintersectsthoserelevanttoDODprinting.26Thetypicalrangeofdropsize(radiusfrom5to50mm)andvelocity(1v10ms-l)issuchthattheinitialdef

15、ormationofthedropwillbecontrolledbydynamicimpactandviscousdissipationprocesses.6,18,26However,thisinitialstageofdropdeformationisexpectedtohavefinishedafterafewmsandsubsequentspreadingtoequilibriumwillbedrivenbycapillaryforces.27Aschematicrepresenta-tionofthetimescalesassociatedwithdropdeformationaf

16、terimpactispresentedinFig.3.Thedynamicprocessesofdropimpactoccuroveratimescaleofms.26Firstthedropdeformsonimpactwithitskineticenergyconvertedintonewsurfaceareaasthedropdeforms,someenergyisabsorbedthroughviscousdissipation.Iftheimpactconditionsaresuchthatsplashingdoesnotoccur(asisnormalwiththeconditi

17、onsofinkjetprinting),thedropmayrecoilafterexpansionandoscillatebrieflydissipatingenergy.Meanwhiletheprocessofcapillaryspreadingwilloccur,thishasatimescaleofmsfordropdimensionsconsistentwithinkjetprintingandthefinalequilibriumdropshapeisnormallycontrolledbythisprocess.2546Fig.3.Schematicillustrationo

18、fthetimescalesappropriatetotheprocessesofdropdeformationandspreadingonasubstrateafterimpact.Axesofdiameterandtimearetoarbitrarynon-linearscales.ReproducedwithpermissionfromRef.6.Onceequilibriumhasbeenreached,thedropcanbemodelledasasphericalcapbecausetheBondnumberissufficientlylowthatwemayignorethein

19、fluenceofgravity.Inwhichcasetheequilibriumcontactdiameterofthedrop,deqm,canbecalculatedwith(2a)deqm=d,where=2taneqm3+tan2eqm-1/3(2b)wheredisthediameterofthedropinflightandeqmistheequilibriumcontactangle.Foranisolateddropofpuresolvent,wewouldexpectthedropdiametertodecreaseandthecontactlinetoretractat

20、aconstantrecedingcontactangleduringevap-oration.However,forthecaseofparticlesinsuspension,thebehaviourofaliquiddropisdifferent.Solventevaporationdoesnotoccuruniformlyfromthesessiledrop.Atlowcontactangles,thefluidclosetothecontactlineisadjacenttoalargedrysurfaceandthisenhancesthetransportofthesolvent

21、vapourpromotingfasterevaporation.Thisleadstoaringofparticlescomingoutofsuspensionandthepresenceofthisdrieddepositpinsthecontactlineandpreventsitretracting.Thiscontactlinepinningresultsintherecedingcontactangledecreasingassolventisremoved.Itcanalsoresultinaflowofparticlestothecontactline,leadingtosus

22、pensionsegregationandaringdeposit;thisisaphenomenonknownasthecoffeestaineffect.28Wewillreturntothecoffeestainphenomenonlaterinthisarticle.Oneeffectofcontactlinepinningduringdryingisthatthefootprintorequi-libriumdiameterofthespreaddropofceramicinkwilldefinethediameterofthedrieddepositonthesurfaceaftersolventevaporation.Inordertoprinttwo-dimensionalpatternsitisnecessarytoallowadjacentdropletstointeractandcoalesce.Itisadvanta-geousforthesedropstointeractwhileinaliquidstatebecausesurfacetensionforceswillresultinasmo