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TSINGHUASCIENCEANDTECHNOLOGYISSN1007-021404/38pp24-28Volume14,NumberS1,June2009PerusingPiezoelectricHeadPerformanceinaNew3-DPrintingDesignRAHMATISadegh,SHIRAZIFarid†,**,BAGHAYERIHesam†MechanicalEngineeringGroup,FacultyofEngineering,AzadIslamicUniversity,MajlesiBranch,Iran;†MechanicalEngineeringDepartment,KhajeNasirToosiUniversity,Tehran,IranAbstract:Rapidprototyping(RP)isacomputerizedfabricationtechnologythatadditivelybuildshighlycom-plexthree-dimensionalphysicalobjectslayerbylayerusingdatageneratedbycomputer,forexampleCADordigitalgraphic.Three-dimensionalprinting(3DP)isoneofsuchtechnologiesthatemployink-jetprintingtechnologyforprocessingpowdermaterials.Duringfabrication,aprinterheadisusedtoprintaliquidontothinlayersofpowderfollowingtheobject'sprofileasgeneratedbythesystemcomputer.Thisworklooksatredesigning3DPmachine,usingpiezoelectricdemand-modetechnologyheadinordertoimproveaccuracy,surfacefinishingandcolorqualityofconstructedmodels.Thelayerscreatedwithaforesaidsystemarebe-tween25to150µm(stepsof25µm).Keywords:prototyping;three-dimensionalprinting(3DP);piezoelectricheadIntroductionSolidfreeformfabrication(SFF)technologiesaremanufacturing/prototypingtechnologiesthatarechar-acterizedbylayer-by-layeradditionofmaterialtofab-ricatecomponents.Thesetechniquesarealsoknownaslayeredmanufacturingandrapidprototyping.Thelayer-by-layerbuildingapproachallowssignificantlymorecomplexpartstobebuiltinonefabricationstepthanwaspreviouslypossiblethussimplifyingprocessplanning.SFFtechnologythereforecanautomatetheprocessplanningandfabricationofapartundercomputercon-trolsothattheonlyinputneededisasolidmodelofthepart[1,2].Overthelastdecade,manydifferenttechnologiesforSFFhaveevolved.Broadly,theSFFtechniquesavailablecurrentlycanbeclassifiedasstereolithogra-phy,solidfusionandsolidification,laminatedobjectReceived:2008-11-09;revised:2009-03-30**Towhomcorrespondenceshouldbeaddressed.E-mail:s_farid_sh@yahoo.com;Tel:98-912-1350938manufacturing,andpowder-basedtechniques.Theste-reolithographytechniqueselectivelysolidifiesaliquidphotopolymerwhilesolidfusionandsolidificationfuse/meltthematerialanddeposititlayer-by-layer.Thelaminatedobjectmanufacturingtechnologycutsoutlaminatesfromsheetsofpartmaterialandgluesorfusesthemtogether.InmostmethodsofSFF,specialsupportstructuresareneededtosupportoverhangingfeaturesofthepart[1,3].Thetwomainpowder-basedtechniquesthathavebeencommercializedareselectivelasersinteringandthree-dimensionalprinting(3DP)printing.Forpowder-basedmethods,nosupportstructuresaretypicallyre-quiredtocreatecomplexshapes.Powderisselectivelyconsolidatedintoapartandtheremainingpowdercanberemoved.IntheSLSprocess,athinlayerofpowderisdepositedinaworkspacecontainerandthepowderisthenfusedtogetherusingalaserbeamthattracestheshapeofthedesiredcross-section.Theprocessisre-peatedbydepositinglayersofpowderthusbuildingthepartlayer-by-layer.Inthe3DPprocess,abindermaterialselectivelybindspowderdepositedinlayers.RAHMATISadeghetal：PerusingPiezoelectricHeadPerformanceinaNew…25Ink-jetprintinghead(IJH)technologyisusedtoprintthebinderintheshapeofthecross-sectionofthepartoneachlayerofpowder(Fig.1)[4,5].changecausespressure/velocitytransientstooccurinthefluidandthesearedirectedsoastoproduceadropthatissuesfromanozzle(Fig.3)[6,8].Aresultofsimu-lateddropletejectionisshowninFig.4.Fig.13-DPrintingprocessTwokindsofdrop-on-demandheadscanbeusedinIJHsystems,piezoelectricandthermalheads[6],andthethermalheadsareusedincurrent3DPsystems.Sincethermalheadshavesomedrawbacks,hencepiezoelec-tricheadhasbeenemployedfornewgenerationof3DPmachines.Inaddition,piezoelectrictechnologycanhelptoinjectthelivecellsintovitaltexturesinordertocreatebones,membersanddentureswithoutanychemicalorphysicalchangesincells.1Ink-jetHeadTechnologies1.1ThermalheadsInthermalsystemsthereisaheatingelementasathin-filmresistor.Whenanelectricalpulseisappliedtothehead,ahighcurrentpassesthroughthisresistorandthefluidincontactwithitisvaporized,formingavaporbubbleovertheresistor.Thisvaporbubbleexpandsinfluidreservoirandisejectedasadropletthroughthenozzle(Fig.2)[6,7].Fig.2Schematicofathermalhead1.2PiezoelectricheadsInthistypeofsystemavolumetricchangeinthefluidreservoirisinducedbytheapplicationofavoltagepulsetoapiezoelectricmaterialelementthatiscou-pled,directlyorindirectly,tothefluid.ThisvolumetricFig.3SchematicofapiezoelectricheadFig.4Aresultofsimulateddropletejectioninpiezo-electricheads[9]Whenavoltagepulseisappliedinthedirectionor-thogonaltothepolarizationdirectionofthepiezoelec-tricelement,itisdeformedandthefluidinthechannelreservoirispressurized.Whenthepressurewavegen-eratedinthechannelisreflectedbetweennozzleandcommonfluidchamberandresonated,thepressureap-pliedtothenozzlechangeintime,andasaresultdrop-letisejected[9].1.3ComparisonbetweenthermalandpiezoelectrictechnologyThermaldemand-modeink-jetsystemscanachieveex-tremelyhighfluid-dispensingperformanceataverylowcost.However,thisperformance/costhasbeenachievedbyhighlytailoringthefluid:thermalink-jetsystemsarerestrictedtofluidsthatcanbevaporizedbytheheaterelement(