增材制造技术-第4章-液态树脂光固化成形

天津科技大学TianjinUniversityofScience&Technology1.结合流程图，描述快速原型制造技术的工艺过程。2.立体光刻快速原型制造技术的工作原理、系统组成，以及各主要部分的控制原理？3.目前立体光刻主要采用哪种类型的激光器，它的波长处于什么区段?为什么必须采用这种激光器?4.SLA快速原型制造技术中,为什么必须保证激光扫描速度与其功率自动匹配?应该如何匹配?5.叙述光学振镜式(偏转镜扫描)激光扫描系统和纯机械式扫描系统的原理，试分析它们的优缺点。思考题逆向工程与快速成形技术ReverseEngineeringandRapidPrototypeTechnology天津科技大学TianjinUniversityofScience&Technology第4章液态树脂光固化成形技术天津科技大学TianjinUniversityofScience&Technology天津科技大学TianjinUniversityofScience&Technology快速成型加工（制造）过程天津科技大学TianjinUniversityofScience&Technology天津科技大学TianjinUniversityofScience&Technology1.TessellationThesurfacesofastandardCADfilearetessellated.表面网格化ForvisitorstoourstudioIexplainthatit’slikethrowingafish-netstockingoverthesurfaces,convertingthemaseaof~10,000triangles.In19873DSystemscalledthisfileoftrianglesthe--andlikemanythishasremainedinusesincethenandfurthermoreadoptedsuchasFDM.天津科技大学TianjinUniversityofScience&Technology2.SlicingThefileoftrianglesissenttotheprototypingmachineandsortedintolayersbythez-dimensionofthetriangles.Again,tovisitors,IexplainthisislikeslicingtheoriginalCADmodelintoastackofpancakes.天津科技大学TianjinUniversityofScience&Technology3.LayerbylayerOncethefirstlayeriscured,theelevatorjogsdownafewtenthsofamillimeterLiquidflowsoverit,andthenthelaserbeginsworkonthesecondlayerwhich,withthecorrectcontrols,fusestothefirstlayer.Theprocessisrepeatedmanytimes;layersaccumulateoverseveralhoursuntiltheobjectisformedTheelevatorrises;andlikeExcalibur’ssword,theobjectappearsfromthehoney!Curingandhandfinishingarefinallyneeded.天津科技大学TianjinUniversityofScience&TechnologyRemovesupportstructuresTwostepcleaningprocessAcetonebath2-PropanolwashCureinUVovenAcetonen.[化]丙酮4、PostProcessingPolymerization聚合Liquidresin(CibatoolSL5170)convertedtosolidpolymeruponexposuretoUVlightPhotopolymerPhotoinitiatorabsorbslaserenergy,formsreactivecationicspecies,initiatepolymerizationprocessEpoxybasedmonomers单体andoligomers低聚物polymerizeuponexposuretocationicspecies天津科技大学TianjinUniversityofScience&Technology快速成型的基本过程天津科技大学TianjinUniversityofScience&Technology1、CAD三维模型建立快速成型技术是由CAD模型直接驱动。因此，要建立任何的快速原型必须从CAD模型开始。而绝大部份的快速成型系统只接受STL档案为输入途径。而目前大多数的CAD商业软件均能将其CAD模型转换成STL档案。如ProEngineer,UG等。2、CAD三维模型Z向离散这是一个分层/切片的过程，由于快速成型是按照其分层截面轮廓来进行加工，因此加工前必须从三维模型沿Z方向每隔一定间距进行切片处理，以便提取截面的轮廓。而分切的距离越少，精度就越高，但成形时间则越长。分层的厚度通常由0.05mm–0.3mm之间，最常用的分切层厚为0.1mm巳得到相当不错的曲面。快速原型的基本成型过程天津科技大学TianjinUniversityofScience&Technology3、层片信息转换处理当分层工序完成之后，必须把截面轮廓的几何形状信息转换成控制成型机的运动数控代码，如SLI及CLI档案等，才能进行加工。各种快速成型系统都带有切片外处理软件。4、截面加工计算机会根据分层处理的截面轮廓进行加工，成型系统会在X-Y平面内自动按截面轮廓进行扫描，得到一层层实体截面。5、堆积层面当一层加工完成之后，成型机工作台会下降一个层厚的距离，再加工新的一层，反复进行以上动作直至整个原型加工完成。6、后处理从成型机中取出成型件，进行清洗、去除支撑(如有需要)、加强固化、打磨、着色等，以达致所需的要求。快速原型的基本成型过程天津科技大学TianjinUniversityofScience&Technology快速成型方法SLA1、光固化成型原理2、光固化成型系统3、光敏树脂的固化特性4、成型工艺5、光固化成型精度天津科技大学TianjinUniversityofScience&TechnologyCuringofaphotopolymerwithalowpowerlaser.Thephotocurableliquid,resemblinghoneyinappearance,iskeptinavatandthelaserbeginstoscanthetopsurface.Thiscuresaninitiallayer,resemblingiceformingonapond,Thelayerismadetositonamechanicalelevator-platformjustbelowthesurface.1、光固化成型原理背景资料StereolithographyPatentedin1986,stereolithographystartedtherapidprototypingrevolution.Thetechniquebuildsthree-dimensionalmodelsfromliquidphotosensitivepolymersthatsolidifywhenexposedtoultravioletlight.Asshowninthefigurebelow,themodelisbuiltuponaplatformsituatedjustbelowthesurfaceinavatofliquidepoxyoracrylate丙烯酸resin.Alow-powerhighlyfocusedUVlasertracesoutthefirstlayer,solidifyingthemodel’scrosssectionwhileleavingexcessareasliquid.背景资料Next,anelevatorincrementallylowerstheplatformintotheliquidpolymer.Asweeperre-coatsthesolidifiedlayerwithliquid,andthelasertracesthesecondlayeratopthefirst.Thisprocessisrepeateduntiltheprototypeiscomplete.Afterwards,thesolidpartisremovedfromthevatandrinsedcleanofexcessliquid.Supportsarebrokenoffandthemodelisthenplacedinanultravioletovenforcompletecuring.StereolithographyApparatus(SLA)machineshavebeenmadesince1988by3DSystemsofValencia,CA.Tothisday,3DSystemsistheindustryleader,sellingmoreRPmachinesthananyothercompany.Becauseitwasthefirsttechnique,stereolithographyisregardedasabenchmarkbywhichothertechnologiesarejudged.Earlystereolithographyprototypeswerefairlybrittleandpronetocuring-inducedwarpageanddistortion,butrecentmodificationshavelargelycorrectedtheseproblems.背景资料Highlights拔萃,集锦(精采会议文献选辑)ThefirstRapidPrototypingtechniqueandstillthemostwidelyused.Usesalight-sensitiveliquidpolymer.Requirespost-curingsincelaserisnotofhighenoughpowertocompletelycure.Long-termcuringcanleadtowarping扭曲.Partsarequitebrittleandhaveatackysurface.Nomillingstepsoaccuracyinzcansuffer.Supportstructuresaretypicallyrequired.Uncuredmaterialcanbetoxic.VentilationisamustTackyadj.有些粘的,缺乏教养或风度的,俗气的Toxicadj.有毒的,中毒的Ventilationn.通风,流通空气背景资料Uncuredresinisremovedandthemodelispost-curedtofullycuretheresin.Becauseofthelayeredprocess,themodelhasasurfacecomposedofstairsteps.Sandingcanremovethestairstepsforacosmeticfinish.Modelbuildorientationisimportantforstairsteppingandbuildtime.Ingeneral,orienti