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OpenSLS:一個(gè)開放源碼的激光燒結(jié)實(shí)驗(yàn)平臺(tái)3D打印咨詢網(wǎng)【3D打印咨詢網(wǎng)編者按】國(guó)內(nèi)的FDM和SLA的diy打印機(jī)已經(jīng)有不少了,但是SLS的還不多見,而在2014年底SLS打印技術(shù)專利開放后,國(guó)外已經(jīng)涌現(xiàn)不少DIY愛好者,也獲得了不少成績(jī),下面介紹一種比較簡(jiǎn)單的、門檻也比較低的OpenSLS打印機(jī)制作過程。希望對(duì)3D打印機(jī)愛好者是一個(gè)很好的參考。注:本網(wǎng)致力于3D打印專業(yè)技術(shù)和行業(yè)發(fā)展研究,歡迎愛好者加入我們的翻譯隊(duì)伍,一起為DIY愛好者提供高價(jià)值的專業(yè)技術(shù)資料。(QQ:1472294842,備注“翻譯”)為了確保對(duì)讀者原文的研讀,這里保留了原文,方便查看相關(guān)的硬件器件或資料的來源鏈接。另外,也方便發(fā)現(xiàn)錯(cuò)漏之處及時(shí)與我們聯(lián)系?。≦Q:1472294842,備注“翻譯問題”)本文原文地址:/wiki/OpenSLS#IntroductionOpenSLS:一個(gè)開放源碼的激光燒結(jié)實(shí)驗(yàn)平臺(tái)Introduction簡(jiǎn)介OpenSLSprintemergingfromthebuildchamber.OpenSLS打印機(jī)從構(gòu)建室制作而來。OpenSLSisaplatformforexploringtheselectivelasersinteringprocessandafunctioningprototypeSLS3Dprintercapableoffabricatingobjectsinavarietyofmaterials.ItwasdevelopedattheAdvancedManufacturingResearchInstitute(AMRI)andwasfundedbyDr.JordanMiller'slabformicrophysiologicalsystemsandadvancedmaterials.Anoverviewofthisprojectandtheresearchinwhichitwillbeusedcanbefoundhere.OpenSLS是探索選擇性激光燒結(jié)工藝和SLS3D打印機(jī)功能樣機(jī)加工各種材料對(duì)象能力的平臺(tái)。它是先進(jìn)制造技術(shù)研究所(AMRI)研制的,由喬丹米勒博士的實(shí)驗(yàn)室資助,實(shí)驗(yàn)室是進(jìn)行微觀生理系統(tǒng)和先進(jìn)材料研究的。這個(gè)項(xiàng)目的一個(gè)綜述和將會(huì)被用到的一些研究可以在這里找到。Thisprojectisuniqueinthatitappropriatesexisting,affordablelaserhardware,namelylasercutters,foruseasintheSLSprocess.Thischangedthenatureofthechallengefromoneofprocurement(ie,wheretofindasufficientlypowerfullaserandoptics)tooneofintegration,modularhardwaredesign,andmaterialdevelopment.TheOpenSLShardwareisdesignedtobeadrop-inpowdermanagementmodulewhosesolepurposeistosynchronouslylayoutlayersofpowderforthelasermotionsystem(thelasercutter'sgantryandlaser)tosinterormelt.Byadaptingcommercialandwidelyavailablelasercuttersforthisprocess,thebarriertoentryforthistechnologycanbelowered.這個(gè)項(xiàng)目是獨(dú)特的,它提供利用現(xiàn)有的、負(fù)擔(dān)得起的激光硬件,即把激光切割機(jī)用于燒結(jié)工藝。這改變了挑戰(zhàn)的性質(zhì)為從采購(比如,在哪里可以找到一個(gè)足夠強(qiáng)大的激光和光學(xué)器材)到集成的、模塊化的硬件設(shè)計(jì)和材料開發(fā)。OpenSLS硬件被設(shè)計(jì)成為裝粉管理模塊,其唯一目的是一邊鋪粉,一邊讓激光系統(tǒng)(激光切割機(jī)的機(jī)架和激光)燒結(jié)或熔化。通過采用市場(chǎng)上和廣泛使用的激光切割機(jī)做這個(gè)過程,這使得SLS打印技術(shù)的進(jìn)入壁壘降低。SAFETY安全BecauseSLSisaninherentlyhigh-energyprocessinvolvingapowerfulinvisiblelaser,CNCequipment,andhazardousmaterials,itshouldnotbetreatedlikethemorefamiliarextrusion-basedmachines.Thisisaverydangerousprocess.Muchcangowrong.Ifyoudecidetoexplorethistechnology,pleaseexerciseextremecaution:thepotentialforlastingbodilyharmisrealandever-presentandshouldtakenveryseriously.因?yàn)镾LS是一個(gè)固有的高能的過程,涉及一個(gè)強(qiáng)大的看不見的激光、數(shù)控設(shè)備、有害物質(zhì),它不應(yīng)被當(dāng)作我們很熟悉的基于擠壓的機(jī)器。這是一個(gè)非常危險(xiǎn)的過程,很多人會(huì)出錯(cuò)。如果你決定去探索這個(gè)技術(shù),請(qǐng)有心理準(zhǔn)備:身體傷害的可能性是真實(shí)的、時(shí)刻存在的,應(yīng)該非常謹(jǐn)慎地對(duì)待。LaserSafety激光安全性Thelasersusedinlasercuttersareincrediblypowerful--literallytensofthousandsoftimesmorepowerfulthanthepocketlaserpointersthatalreadybearaeye-safetywarninglabel.Thisisawholeotherclassoflasersafety.Youreyesarenolongertheonlythingatrisk.Inadditiontothedangerofthelaserradiation,thegastubethatemitsthelaserisdrivenbyahighvoltagepowersupplywithvoltagesupwardsof30kV.Extremecareshouldbetakenwhenworkingonthelasercutterelectronicsasthehighvoltagesupplyholdschargeforsometimeafterthelasercutterispowereddown.SamGoldwasserhaspreparedanexcellentpageonlasersafety,includinganextensivesectiononDIYlasersandthesafetychallengesthere-in.Pleasereadthroughitbeforeattemptinganyoftheworkdescribedhere.用于激光切割機(jī)的激光是令人難以置信的強(qiáng)大——簡(jiǎn)直比口袋里激光指示器的能量高成千上萬倍,口袋激光指示器已經(jīng)滿足用眼安全警示指示,而這完全是另一個(gè)激光安全級(jí)別。你的眼睛不再是唯一危險(xiǎn)的事情,除了激光輻射的危險(xiǎn),發(fā)射激光的氣管通過一個(gè)30kV以上的高電壓電源驅(qū)動(dòng)。工作時(shí)對(duì)激光切割機(jī)電子部分應(yīng)該特別注意,激光切割機(jī)斷電后,讓高壓電源保持充電一些時(shí)間。SamGoldwasser準(zhǔn)備了一個(gè)激光安全的優(yōu)秀的網(wǎng)頁,包括一個(gè)DIY激光器擴(kuò)展領(lǐng)域和安全挑戰(zhàn)。請(qǐng)?jiān)趪L試這里的所有工作之前先閱讀它。MaterialsHazards材料的危害FinelypowderedmaterialsareoftenVERYFLAMMABLEorEXPLOSIVEinadditiontobeingaseriousrespiratoryhazard.Extremecareshouldbetakenwhenhandlingpowderedmaterials.Staticshocksareinsomecasesenoughenergytoignitecloudsofdust,causinganexplosion.Additionally,thisfirstprototypedoesnotincorporateinert-gasshieldingofthepowder-laserinterface,which,forsomematerials,couldbeverydangerous,especiallyifanypowderbecomesairborne.最后,細(xì)粉狀的材料往往是非常易燃易爆的,而且有嚴(yán)重的呼吸系統(tǒng)危害性,處理粉狀材料時(shí)應(yīng)特別小心。靜電沖撞在某些情況下有足夠的能量點(diǎn)燃?jí)m云,引起爆炸。此外,這第一版原型并不包含粉末激光接口惰性氣體保護(hù)裝置,這對(duì)一些材料是很危險(xiǎn)的,尤其是粉末散播到空氣中。ProcessOverview工藝概述Laser-basedadditivemanufacturingtechnologiesarealittledifferentfromthemorefamiliarmelt-extrusiontechniques.Ofchiefinterestistheflexibiitythatcomeswithusingapowderedfeedstock.Manynon-thermodecomposingmaterialshavethepotentialforcompatibilitywiththelaser-formingprocesses.基于激光的增材制造技術(shù)與比較熟悉的熔融擠出技術(shù)有點(diǎn)不同。主要有趣的是使用粉末狀的進(jìn)料存貯帶來的復(fù)雜性。許多非熱解材料與激光成形工藝有潛在兼容性。Terminology術(shù)語ThetermSLSisusedoftenbroadlytodescribeanumberoflaser-formingprocesses.Itissometimedistinguishedfromselectivelaser-melting(SLM)becausethereisacleardifferencebetweenthetwosolidificationmethods.Laser-meltinginvolvesfullymeltingthepowderedmaterialtoitsliquidphase,whichresultsinafully-densepart.Laser-sinteringreliesonveryhighthermalgradientstoliquify(thoughnotinallcases)thesurfaceofthepowderparticles,bondingtoeachother,butleavingsmallvoidsbetweenthebondedparticles.Intermsofbondingmechanisms,thisdistinctionisimportant,butintermsofterminology,laser-sinteringandlaser-meltingareoftenusedsomewhatinterchangeably.Kruthetal,2005proposed12distinctbindingmechanismsinthefamilyoflaser-sintering/laser-meltingprocesses.Theimportantpointthoughisthatthedistinctionbetweenmechanismsismainlymaterial-dependentandbasedonparticlesize,geometry,packingstructure,andthermalconductivityaswellasthebedtemperature,laserpower,spotsize,andatmosphere.Buttheimplicationsofthefinerpointsoflaser-formingterminologywithrespecttothisprojectareinteresting:thissystemhasbeendemonstratedsuccessfullywiththelaser-meltingprocess,buthasyettobedemonstratedwiththelaser-sinteringprocess.術(shù)語SLS經(jīng)常廣泛地指激光成形工藝系列。它有時(shí)是區(qū)別于選擇性激光熔融(SLM)因?yàn)閮煞N凝固方法之間有明顯的差異。激光熔融包括完全熔化粉末材料到液態(tài)的過程——最后形成一個(gè)完全致密的狀態(tài)。激光燒結(jié)依賴很高的熱梯度來液化(雖然不是在所有情況下)表層的粉末顆粒,使其彼此粘結(jié),但粘結(jié)顆粒之間留下小的空隙。就粘合機(jī)制而言,這個(gè)區(qū)別是重要的,但從術(shù)語而言,激光燒結(jié)、激光熔化通常有點(diǎn)相同的含義。Kruth等人,2005年對(duì)激光燒結(jié)/激光熔化過程,提出了12種不同的約束機(jī)制。然而重要的一點(diǎn)是,機(jī)制之間的區(qū)別主要是材料相關(guān)的,基于顆粒大小、幾何、填充物結(jié)構(gòu)、導(dǎo)熱性以及床層溫度、激光功率、光斑大小和空氣。但就這個(gè)項(xiàng)目定義激光成形術(shù)語的細(xì)節(jié)很有趣:該系統(tǒng)已被成功證明是激光熔融過程,但尚未被證明是激光燒結(jié)過程。

[page]Mechanics機(jī)械Theprocessoflaser-sinteringbeginswithaverysimplesystem:alaserinjectingenergyintoagroupofparticlesofsomemass.However,manyfactorsinfluencehowthelaserenergyisabsorbed:particleshape,size,packingdensityandconfiguration,materialabsorption,reflectivity,andtransmission,atmosphere,energydensity,beamprofile,andspotdiameteraresomeofthemajorfactors.激光燒結(jié)過程開始于一個(gè)非常簡(jiǎn)單的系統(tǒng):激光能量注入到一批有質(zhì)量的粒子。然而,許多因素影響激光能量的吸收:顆粒的形狀、大小、密度、結(jié)構(gòu),材料的吸收、反射、透射、空氣、能量密度、光束輪廓、和光斑直徑是一些主要的因素。Theparticleshapeaffectshowthepowderbehavesatamacroscale:sphericalparticlesfloweasilyovereachotherandenmasseyieldpowdersthatflowmuchlikealiquid.Moreangularparticlesgiverisetotransient,butstablepackingstructuresandflowinmorestaggered,haltingwaysonthemacroscale.Flakesandmorecomplexplateletscanhavebothfluidflowpropertiesinsomecases,adegreeofself-adhesionorself-entanglement,dependingonthecomplexityoftheformoftheparticles.Thesegeometricfactorscombinewithparticlesizetoinfluenceparticlepackingpatterns,whichinturnplayalargeroleinhowheatistransferredthroughtheparticlesystematthesiteofsintering.Heattransferbetweenbodiesisproportionaltoboththemagnitudeofthetemperaturedifferenceandthecross-sectionalareabetweenthebodies.Particlesize,shape,andpackingpatterndeterminethenumberandsizeofcontactpointsbetweenparticles(Gusarovetal,2003).Themorepointsofcontacttherearebetweenparticles,thebetterheatcanflowthroughthem.顆粒形狀在宏觀程度影響粉末的行為:球形粒子流很容易互相疊加流動(dòng),聚集而生成粉末,就像流動(dòng)的液體。有棱角的顆粒流會(huì)引起瞬間的、但卻穩(wěn)定的填充結(jié)構(gòu),更多地以交錯(cuò)、停頓的方式(在宏觀層面看)流動(dòng)。薄片和更復(fù)雜的片晶在某些情況下都可能有流體特性,并有一定程度的自我粘附或自我纏繞,這取決于顆粒形態(tài)的復(fù)雜性。這些幾何因素結(jié)合粒徑共同影響顆粒的聚集形態(tài),從而對(duì)熱量如何穿過燒結(jié)中的粒子系統(tǒng),發(fā)揮了很大的作用。物體之間的傳遞的熱量與溫差大小和物體之間橫截面積的大小成正比。顆粒大小,形狀,和填充模式?jīng)Q定顆粒之間的接觸點(diǎn)的數(shù)量和尺寸(薩洛夫等人,2003)。顆粒之間的接觸點(diǎn)越多,通過它們的熱量就越多。Inadditiontoinfluencingheattransferthroughstaticpowder,particlesizeandshape(anddistributionthere-of)affectshowlaserenergyistransferredtothepowderparticles.Thesurfaceofthepowderbedcanbethoughtofasporous--therearenumerousvoidsbetweenparticlesthatexposeparticlesoneortwolayersdeeperinthebedtothelaser.Thischangestheabsorptiontopology:forasolidmaterial,laserenergywouldbeabsorbedthroughthetwo-dimensionalsurfaceofthesample.Here,laserlightpenetratesdeeperintothematerial,bothreflectingoffofandbeingabsorbedbyparticlesbeyondthesurfacelayer(Simchi,2006).除了靜電粉末影響傳熱,顆粒大小和形狀(分布)影響激光能量如何被傳遞到粉末顆粒。粉末床的表面可以認(rèn)為是多孔的——顆粒之間有無數(shù)的間隙,給激光暴露了一層或兩層以致更深的粉末。這改變了吸收的拓?fù)浣Y(jié)構(gòu):對(duì)固體材料,激光的能量會(huì)通過樣本的二維表面吸收。在這里,激光穿透更深的材料時(shí),既被表面層顆粒反射也被表面層顆粒吸收(Simchi,2006)。Nowwecanbegintoconsidertheimpactoftimeonthesystem.Asthelaserheatsparticlesinathree-dimensionalprofile,thesurfacesoftheparticlesbegintomelt,increasingthecontactsurfacearebetweenindividualparticlesandthroughbondingandeliminatingthematerial-gas-materialjunction,increasingheattransferbetweenparticles.Thiscanbethoughofasachangingoftherateofsinteringwhichisinturndependentontherateofsintering(Simchi,2006).Inotherwords,sinteringacceleratesitselfduetotheincreaseinheattransferthatoccursasparticlesbegintobondtoeachother.現(xiàn)在我們可以開始考慮時(shí)間對(duì)系統(tǒng)的影響。由于激光加熱的是顆粒的三維型面,顆粒的表面開始融化,融化增加了單個(gè)顆粒之間的接觸面,通過粘結(jié)并消減材料之間的氣體空隙,增加顆粒間的傳熱。這雖然可以改變燒結(jié)速度,它反過來又依賴燒結(jié)速度(Simchi,2006)。換句話說,燒結(jié)增速本身依賴于熱傳遞的增加,熱傳遞是當(dāng)顆粒之間開始相互粘合時(shí)發(fā)生的。Inthecaseoflaser-melting,thereisafullphasechangefromsolidtoliquid,whichgivesrisetooneofthemostdifficultchallengesinlaser-sintering/-meltingprocesses:the"ballingeffect,"whichdescribesthetendencyofpowderedmaterialstobeadupintosmallspheresafterbeingheatedbythelaserbeam.Thisisaresultofsurfacetensionevolvingandexercisingashapingforceuponthematerialasitisliquified.Theeffectisverysimilartothesegmentationthatasinglestreamofwaterundergoesasitfalls–thetensiondistributedoveritscylindricalsurfaceisuneven,spatiallyspeaking:thesurfacetensioncreatesaconstrictiveforce,whichduetonaturalvariancesintheshapeofthestream,leadstonecking,whichleadstodropformation.Thedropsassumetheirspherical(ornearlyspherical)shapebecauseitisthelowestenergyshapeforthephysicalsystem:nettensionisthelowest.Thesameforcesthatcreatedropsfromashowerheadareresponsibleforthesmalldropsofmaterialintheballingeffect.在激光熔化的情況下,有一個(gè)從固體到液體的完整的相變過程,導(dǎo)致了激光燒結(jié)/熔化過程一個(gè)最困難的挑戰(zhàn):“球化效應(yīng)“,它描述了粉末材料被激光束加熱后,形成球珠并分解成小球珠的趨勢(shì)。這是由于表面張力的變化和材料液化運(yùn)動(dòng)的成形力所致。效果非常像一個(gè)片段:一個(gè)單一的水流經(jīng)過時(shí)–張力分布在水流柱表面是凹凸不平的,從空間上來:表面張力產(chǎn)生收縮力,收縮力依賴于水流形狀的自然變化,并導(dǎo)致細(xì)頸現(xiàn)象,最后導(dǎo)致液滴形成。水滴我們假設(shè)他們是球形(或近球形),因?yàn)榍蛐问俏锢硐到y(tǒng)的最低能量形狀:網(wǎng)張力是最低的。從一個(gè)淋浴頭形成一滴水的力量完全能勝任從材料的球化效應(yīng)產(chǎn)生小水滴。Hardware硬件Progressinopen-sourcelaser-sinteringtechnologyhasbeenstymiedbyalackofaffordable,high-powerlasersourcesandopticschains.Lasercuttersareincreasinglyaccessibleathackerspacesandarerapidlydroppingincost.Byusinganexistinghigh-precisiongantryandassociatedoptics,lasersource,andpowersupply,themostsignificantbarriertoentryintothistechnologycanberemoved.OpenSLSisarelativelysimplepowder-handlingmodulethatdropsintoalasercuttertocreateaplatformforlaser-sinteringresearch.Thepowdermodulewasdesignedtoconsistlargelyoflaser-cutpartstoallowittobefabricateduponthelasercutterwhosefunctionalityitwillaugment.3DprintedpartsarealsousedextensivelyandnearlyallotherhardwarecanbesourcedfromMcMasterandInventables.Multiplemodulescanbeinstalledintoonelasercutter,allowingfortandemexperimentationinmultiplematerials.開源的激光燒結(jié)技術(shù)的進(jìn)展已經(jīng)因?yàn)槿狈ω?fù)擔(dān)得起的、高功率激光源和光學(xué)鏈而遇到阻礙。激光切割機(jī)越來越容易在創(chuàng)客空間接觸到,成本也在迅速下降。利用現(xiàn)有的高精密龍門架和相關(guān)的光學(xué)器件、激光源和電源,進(jìn)入該技術(shù)最顯著的障礙可以被移除。OpenSLS是一個(gè)相對(duì)簡(jiǎn)單的粉末處理模塊,用一個(gè)激光切割器來創(chuàng)建一個(gè)用于激光燒結(jié)的研究平臺(tái)。粉末模塊設(shè)計(jì)主要由激光切割零件組成,使得可以從激光切割機(jī)制作出激光打印機(jī),使其功能增強(qiáng)。3D打印的部件也被大量使用和幾乎所有其他的硬件可以來自McMaster和inventables。多個(gè)模塊可以安裝到一個(gè)激光切割機(jī),多種材料可以串行進(jìn)行實(shí)驗(yàn)。

[page]PowderModule粉模塊TheR1hardwaresupportedwaxsinteringandwasavaluablesourceofdesignandprocessrefinement.R1硬件版本支持蠟燒結(jié),對(duì)設(shè)計(jì)和工藝改進(jìn)是一個(gè)有價(jià)值資源。R1HardwareR1的硬件TheR1powdermoduleconsistsoftwopistonsofidenticaldimensions,eachdrivenbyalead-screwofdifferentpitch.ThefeedpistonisdrivenbyanM12x3.0AcmescrewwhiletheprintpistonisdrivenbyaM8x1.25threadedsteelrod.Thedifferenceinpitcheswasintendedtoallowthetwopistonstobedrivenoffthesamemotorcontrolchannelinadirection-reversedparallelconfiguration,movingdifferentdistancessimultaneouslyinoppositedirections.However,the"transferratio"betweenthepistonsisactuallyquitedependentonthematerialinquesitonaswellas,tosomedegree,thegeometryoftheobjecttobeprinted.R1粉模塊由兩個(gè)相同的尺寸活塞組成,每一個(gè)活塞由不同螺距絲杠驅(qū)動(dòng)。進(jìn)給活塞通過m12x3.0的梯型螺紋絲杠驅(qū)動(dòng),打印活塞通過m8x1.25螺紋鋼棒驅(qū)動(dòng)。兩個(gè)活塞的螺距不同是為了兩個(gè)活塞被驅(qū)動(dòng)離開相同的馬達(dá)控制器通道,以方向平行相反的配置,同時(shí)在相反的方向移動(dòng)不同的距離。然而,活塞之間的“轉(zhuǎn)移率”實(shí)際上還相當(dāng)依賴于材料的問題,在某種程度上,在于打印件的幾何形狀。TheR1powderdistributorfirstusedacable-drivencounter-rotatinganodizedAluminumrodtospreadprintpowderduringlayerdistributions.Tensionednylonmonofilamentwrappedaroundstaticpulleyscoupledtotheendsofthedistributorrodenforcedcounter-rotationduringtranslation,whichwasaccomplishedbybelt-drivenbushingsateachendoftheAluminumrod.Thisallowedforaonedegreedrivetoeffecttwodegreesofmotion.Laterexperimentsindicatedthatamuchsimplerpowderdistributorperfromedbetterthanthecounter-rotatingone.Astainlesssteellabspatulaprovidedthebestresultsinbothwaxandnylon.Whilethepowderdistributorusestwosteppermotors(solelyforthelackofanappropriately-sizedGT2timingbelt),thesetoocanbedriveninparalleltoreduceagainthenumberofmotorchannelsneededtocontrolthesystem.R1的粉末分配器首先用電纜驅(qū)動(dòng)的反向旋轉(zhuǎn)的電鍍鋁桿,用以鋪開打印用的粉末。拉緊的尼龍單絲纏繞靜滑輪耦合到鋁桿的一端,使鋁桿在移動(dòng)的同時(shí)執(zhí)行反向旋轉(zhuǎn),完美結(jié)合鋁桿兩端的皮帶帶動(dòng)的軸襯。這允許一級(jí)驅(qū)動(dòng)作用給兩級(jí)運(yùn)動(dòng)。后來的實(shí)驗(yàn)表明,一個(gè)更簡(jiǎn)單的粉末分配器比這個(gè)反向旋轉(zhuǎn)分配器更好。一個(gè)不銹鋼實(shí)驗(yàn)室刮刀給蠟和尼龍材料提供了最好的結(jié)果。而粉末分配器使用兩個(gè)步進(jìn)電機(jī)(僅為缺乏一個(gè)適當(dāng)大小的GT2同步齒型帶),這些也可以并行驅(qū)動(dòng)從而再次降低電機(jī)通道的數(shù)量,滿足控制系統(tǒng)的需求。R2HardwareR2的硬件TheR2hardwareincorporatesmuchofwhatwaslearnedfromworkingwiththeR1module.R2的硬件增加了很多從R1模塊使用獲得的經(jīng)驗(yàn)。Thesecondrevisionofthehardwareaddressesbothmechanicalissuesrelevanttothelasersinteringprocessandusabilityconsiderationswiththefollowingfeatures:硬件的第二版修訂解決機(jī)械問題,包括關(guān)于激光燒結(jié)過程,以及關(guān)于以下功能可用性的考慮:Aluminumbuildchambercompatiblewithsiliconeheatingpads鋁構(gòu)建室兼容硅樹脂加熱墊Inertgasbuildvolumeshieldingviaperforatedbuildplate惰性氣體通過多孔板構(gòu)建大量屏蔽罩Level-ablebuildplate打印板的水平能力Fluidizedbedpartextraction流化床部分提取Modularandadaptabledistributorsystem模塊化和適應(yīng)性強(qiáng)的分配系統(tǒng)Integratedelectronicsandpowersupply集成的電子和電源Internalpowdercaptureandstorage內(nèi)部粉末捕獲和存儲(chǔ)Linearmotionhardwarebetterisolatedformpowder線性運(yùn)動(dòng)硬件更好地隔離于粉末Adjustablepowderdistributorblade可調(diào)葉片粉末分配器Properlyconstraineddistributionsystemonlinearrailstoenforcelayerheight適當(dāng)約束分配系統(tǒng)的線性導(dǎo)軌來縮小層高度Integrationbracketsforsecuringpowdermoduletolasercutterframe給激光切割框架集成支架來提高粉末模塊的安全性Modularconstructionforeasycleaningofthepowderductingandprintpiston模塊化結(jié)構(gòu),易于清潔粉管道和打印活塞Integrateddistributorwipercleaningbrushestodislodgeanyadheredclumpsorpowder安裝刮片清潔刷給分配器,去除分配器上附著的塊狀或粉末Moduleisfree-standingwhenremovedfromthelasercutterforeasymaintenance/repair模塊是獨(dú)立的,可以從激光切割機(jī)上取下來,易于維護(hù)/維修LaserCutter激光切割機(jī)ThelasercutterbeforeanymodificationsweremadetoitsZ-stageorelectronics.之前的任何修改都合入了Z級(jí)或電子器件。R2hardwareinstalledinalasercutter(powderductingremovedandrestingontheleft).R2版本硬件安裝在激光切割機(jī)上(移動(dòng)粉末管道的位置,放在左邊)。ThelasercutterwasprocuredthroughSeeMeCNC.ItisanamelessChineseimportsystemwithan80Wtube,a600mmx900mmworkenvelope,andsurprisinglycapableaccompanyingsoftware.Anylasercutterthatusessteppermotors(andthat'smostofthem)shouldbecompatiblewiththeelectronicsstackusedhere.激光切割機(jī)是通過SeeMeCNC采購。這是一個(gè)無名的中國(guó)進(jìn)口系統(tǒng),一個(gè)80W電子管,一個(gè)600mm×900mm工作范圍,和有驚人的能力的附帶的軟件。任何采用步進(jìn)電機(jī)的激光切割機(jī)(這是大多數(shù)人)應(yīng)與這里使用的電子堆棧兼容。LaserPower激光功率Bothan80Wattand40WatttubeweretestedforusewiththeOpenSLSpowdermodule.Bothtubesonlyemittedaboveathresholdcurrentlevel,creatingafirmlowerboundtothepowerlevelsthatcouldbeexplored.Thelowestattainablepowerwas2.4Wattsonthe80Watttubeandapproximately100milliWattsonthe40Watttube.AscanbeseenbelowintheplotsoflaserpowerversusPWMcontrolsignalvalue,linearityvariesdependingonpowerrange.Bothtubesexhibithighervariabilityathigheroutputpowers,thoughthe80Wtubedistinguishesitselfbyapowersurgebetween14and40Watts,duringwhichitreachespowersmeasuredover150Wattsbeforereturningtoamorepredictablelinearregime.Thelowerendofthe40Wtube'spowerrangeallowedforthefinestgraduationofpowerlevelsforexploringrelativelylowlaserpowercarbohydratesandpolymers.一個(gè)80瓦和40瓦電子管在OpenSLS粉末模塊上的使用都被進(jìn)行了測(cè)試,兩個(gè)電子管都只在閾值電流水平以上發(fā)射電子束,能生成一個(gè)穩(wěn)定的下界功率水平以便能夠探測(cè)。最低能達(dá)到的功率是2.4瓦/80瓦電子管,和大約100毫瓦/40瓦電子管。通過PWM控制信號(hào)變量相應(yīng)的激光功率圖,線性變化取決于功率范圍,我們可以看出,兩個(gè)電子管在較高的輸出功率都具有較高的變異性,雖然80W電子管區(qū)別在于有14w和40W之間的電源浪涌,其間它達(dá)到超過150瓦功率才回到一個(gè)可預(yù)測(cè)的線性狀態(tài)。下面的40W電子管的功率范圍對(duì)探索相對(duì)較低的激光能量的碳水化合物和聚合物,是極好級(jí)別的功率水平Atlowpowers,thelaserisrelativelylinear,butthereisagradualincreaseinpoweroverthefoursequentialtrials,eachlastingapproximately15minutes.在低功率,激光是相對(duì)線性的,但在四序貫試驗(yàn)中,功率逐漸增加,每次持續(xù)約15分鐘。Overamuchbroaderpowerrange,thelaserdeviatesfromthelinearityseenatlowerpowers.在一個(gè)更廣泛的功率范圍,激光在低功率出現(xiàn)線性偏離。The80Wlaserisalsorelativelylinearatthelowerendofitspowerrangeandalsoexhibitsthegradualincreaseinoutputpowerovertheseriesoffourstrialsthatthe40Wlaserdid.80W激光在低功率范圍也相對(duì)呈線性,也表現(xiàn)出在四序貫試驗(yàn)中,輸出功率逐漸增加的情況,如同40W激光的實(shí)驗(yàn)結(jié)果。Athigherpowerlevels,specificallythosebetween14and40Watts,outputpowerisincrediblyhighandunpredictablebeforeitreturnstoanewlinearregime.在更高的功率水平,特別是那些14和40瓦之間,輸出功率是非常高的和不可預(yù)知的,直到它返回到一個(gè)新的線性狀態(tài)。BOMBOMTheBOMisbeingcompiledandwillbeupsoon.BOM正在編輯,很快會(huì)發(fā)上來。

[page]PrintMaterials打印材料Oneofthepowerfulaspectsoflasersinteringisitsabilitytofabricatepartsoutofmanydifferentmaterials.Thissystemhasbeentestedwitharelativelysmallnumberofmaterialstovaryingdegreesorrigor,fromsimplepoint-meltingtoonedimensionaltracesintering,allthewaytofullthreedimensionalsintering.一個(gè)強(qiáng)大的激光燒結(jié)的方面是它從許多不同的材料制造部件的能力。該系統(tǒng)已經(jīng)針對(duì)相對(duì)小數(shù)量的材料,不同程度或嚴(yán)謹(jǐn)性地通過了測(cè)試,從簡(jiǎn)單的點(diǎn)熔化到一維跟蹤燒結(jié),一直到完整的三維燒結(jié)。MethodsofFabrication制造方法GranularCrystallinePowders粒狀結(jié)晶粉末Ball-millingisawidely-usedprocessforreducingparticlesizeforbrittleandcrystallinematerials.Thelaser-sinteringprocessrequiresfineparticlesforeventraceformationandhigherresolution,butmanymaterialsareonlyavailableascoarsegrains.Byball-millingandsievingtheresults,finepowdersofhomogenousparticlesizecanbemanufacturedinsmallquantities.Iusedasmallrocktumblertostartmakingpowdersandgraduatedtoahigh-capacitytumblerwithasteelbarrelformakinglargerbatchesofpowderusinglargergrindingmedia.球磨機(jī)是一種廣泛使用的減小脆的和結(jié)晶狀材料大小的過程。激光燒結(jié)工藝要求即使是微量的形成和更高分辨率的細(xì)顆粒,但許多材料只提供粗糙顆粒。通過球磨、篩分顆粒材料,均勻大小顆粒的細(xì)粉末可小批量生產(chǎn)。我用一個(gè)小的石頭翻滾器開始制作粉末,并把它升級(jí)為一個(gè)鋼筒制作的大容量滾筒,使用更大的研磨介質(zhì)制作大批量粉末材料。Ascanbeseeninthetwochartsbelow,therearetwogoverningtrendsingrindingmediaselection.First,ahigherratio(byweight)ofgrindingmediatosubstrateyieldshigherfractionsoffinerparticles.Second,largergrindingmedia"grains"outyieldhigherfractionsoffinerparticlesthandosmallergrindingmediaormixturesofsmallandlargegrindingmedia.Bothofthesetrendsmakesenseinthecontextofthecountlesstinyimpactsbetweengrindingmediaandparticlesthatconstitutetheballmillingprocess:highermassgrindingmedialendslendsdelivershigherenergyimpactsandmoregrindingmediameansmoreimpacts.可以看下面的兩個(gè)圖表,有兩個(gè)選擇研磨介質(zhì)的控制趨勢(shì)。第一,底層物質(zhì)中較高比例(重量比)的研磨介質(zhì),能夠生產(chǎn)出較高分?jǐn)?shù)的更細(xì)的顆粒。第二,相比小研磨介質(zhì)或大小研磨介質(zhì)混合物,較大的研磨介質(zhì)“顆粒”產(chǎn)出較高分?jǐn)?shù)的更細(xì)顆粒。研磨介指和顆粒之間無數(shù)微小的碰撞,構(gòu)成了球磨機(jī)過程,在這樣的背景下前面兩個(gè)趨勢(shì)的意義在于:高質(zhì)量的研磨介質(zhì)可以提供更高能量的碰撞,更多的研磨介質(zhì)意味著更多的碰撞。Grindingmediaquantity.png磨礦介質(zhì)quantity.pngGrindingmediatypechart.png磨礦介質(zhì)類型chart.pngWax-basedPowder蠟基粉CandelillawaxcanbepurchasedfromStrahlandPitsch.ForprintingwithlowpowernearIRlaserdiodes,itisnecessarytoblendasmallamountofcarbonpowderintothewaxtoactasanenergyabsorbingpigment.Themixturecanbepreparedbyblending100partswaxwith7partscarbonbyweightandthenworkingthemixturethroughan80meshsievetothoroughlybreakupwaxclumpsandincorporatethecarbon.Thismixtureissensitivetohumidityandbeginstoclumpafterremainingstaticforseveraldays.小燭樹蠟可以從StrahlandPitsch購買。用低功率近紅外激光二極管打印,要混合少量的碳粉到蠟粉中作為能量吸收色素。該混合物可以通過混合重量為100份蠟與7份碳,然后把混合物通過80目篩子,徹底打破蠟粉塊并將其參入到碳粉中。這種混合物對(duì)濕度敏感,靜放幾天后開始結(jié)塊。CandelillaWax小燭樹蠟Candelillawaxhasbeendemonstratedasasapotentiallow-costSLSprintmaterialandwasinvestigatedasapositivecontrolduringOpenSLShardwaredevelopment.TheprintmaterialconsistsofCandelillawaxandcarbonpowderblendedina100to7ratio,inwhichthecarbonpowderactsbothasanenergy-absorbingpigmentforlaserwavelengthinthenearinfraredandalsoasade-clumpingagent.Thelaser-sinteringpreviousdemonstratedin2011byAndreasBastianwasfull-meltinglaserconsolidation,whichleadstohighamountsofcurlingandloweredgedefinitionduetosurfacetensioneffectsofafully-liquidconsolidationzone.Parametersformoretraditionalliquid-phasesinteringofindividualparticleswereinvestigatedviatraversalofthepower/speedparameterspace.Ofthe325power/speedcombinationsattempted,noneyieldedliquid-phasesinteringbetweenindividualparticlesofwax.Instead,imagingof2Dsinteredsurfacesindicatedafinedegreeofballingsufficienttoleadtobindingbetweensmallconsolidatedregionsofparticles,leadingtoabulkcohesionsufficientforprintingdelicateandporousobjects.小燭樹蠟已被證實(shí)為是一個(gè)潛在的低成本的SLS打印材料,被探查在OpenSLS硬件開發(fā)過程中作為陽性對(duì)照。打印材料由小燭樹蠟與碳粉混合在一個(gè)100比7的比例,其中炭粉既作為激光波近紅外線能量吸收色素在,也作為防結(jié)塊介質(zhì)。激光燒結(jié)是2011年由AndreasBastian展示是全激光熔化固結(jié)過程,從而導(dǎo)致大量的卷曲和下邊緣的定義基于表面張力影響完全液體固結(jié)區(qū)。通過遍歷了功率/轉(zhuǎn)速參數(shù)空間,單顆粒更傳統(tǒng)的液態(tài)燒結(jié)參數(shù)獲得研究。通過325個(gè)的功率/速度組合嘗試,沒有一個(gè)在單個(gè)蠟粒子之間產(chǎn)生液態(tài)燒結(jié)。相反,二維燒結(jié)表面成像表明,球化的精細(xì)程度充分導(dǎo)致小固結(jié)區(qū)域的顆粒粘結(jié),導(dǎo)致大量顆粒結(jié)合,足夠打印精致多孔的物體。Thewaxandcarbonmixtureatlowmagnification.在低倍鏡下的蠟粉和碳粉的混合物。Thegearaftercleaningwithcompressedair.Itwasfartoobrittleandporoustosurviveremovalfromthebuildplatform.用壓縮空氣清潔后的齒輪。它太脆和多孔,從構(gòu)建平臺(tái)拆除后很難再利用。Oneofmanyscriptedtraversalsofthepower/speedspace.PowerincreasesinYandspeeddecreasesinX.其中的許多文章中介紹功率/速度知識(shí)。X表示速度減小,Y表示功率增大Asmallgearillustratingtheresolutionandscalethemachinecanproduce.一個(gè)小齒輪可以表明分辨率和衡量機(jī)器可以生產(chǎn)。Athighermagnification,theindividualcarbonandwaxparticlescanbeclearlyseen.高倍鏡下,單個(gè)的碳顆粒和蠟顆粒清晰可見。Uponfurtherexamination,eventhebestprintingparameterswererevealedtobefineballinginsteadoftrueliquid-phasesinteringbetweenparticles.經(jīng)進(jìn)一步試驗(yàn),即使是最好的打印參數(shù),都顯示出很好的球化效應(yīng)而不是顆粒之間真正的液態(tài)燒結(jié)。

[page]Nylon尼龍SamplesofTaulman618sandPA650wereprocuredfromTaulman3DandALMLLC,respectively.Bothnylonsprovedmucheasiertosinterthanthewaxortheisomalt.Likethewax,thefirstlayerneededtobefirmlybondedtothebuildplatform(bluetape,inthiscase),orelsecurlingwoulddisruptpowderdistributionandlayerregistration.Evenso,unsupportedregionsoftheprintedobjectwillcurlanddisrupttheprintlaterintheprintsequenceifofsufficientsizetocatchthedistributorblade.Adheringthefirstlayeroftheprintisawork-aroundtoallowforfurtherexplorationof3Dsintering,butitdoesnotallowforthesamefreedomfromgeometricconstraintsascommercialSLStechniques.Thiswillhavetobeachievedviaheatingthepowderunderaninertatmosphere.從Taulman3D和ALM公司獲得了taulman618s和PA650個(gè)樣品,兩種尼龍都證明比蠟或異麥芽酮糖醇更容易燒結(jié)。像蠟,第一層必須跟構(gòu)建平臺(tái)(藍(lán)色帶,在這種情況下)粘結(jié)牢固,否則首層卷翹會(huì)破壞鋪粉和每層的準(zhǔn)確重合。即便如此,在沒有支撐的打印對(duì)象區(qū)域?qū)⒕砬⑶覕_亂后續(xù)的打印序列,即使有足夠打的尺寸抓住分配器的刀片。粘緊第一層是能夠進(jìn)一步探索3D燒結(jié)的基本工作,商業(yè)SLS技術(shù)有不受幾何約束的自由,但它不同。這需要通過在惰性氣體環(huán)境下加熱粉末來實(shí)現(xiàn)。Theseearlyobjectswerefabricatedwithalaserpowerof400mW,printspeedof58mm/s,layerheightof150microns,and"nozzle"sizeof0.075mm.SeethePA650slic3rprofileintheOpenSLSgithubformoredetailedprocessparameters.ThispowerlevelisquitelowandobviouslytheCO2lasercanemitatmuchhigherpowers.What'simportantisthehighabsorptionefficiencyofnylonat10.6um,thewavelengthofCO2gaslasers.Lowcost,high-powerdiodelasersareinthenearinfraredrange,between808nmand840nm,whichisnoteasilyabsorbedandconvertedintoheatbynylon.Lasersinthebluerangemayhavebetterabsorption.Addinganenergyabsorbingpigment,suchascarbonintheaboveCandelillawaxmixture,maybeeffectivefordiodelaserimplementations.這些早期的組件已經(jīng)是現(xiàn)成的:400MW的激光功率、58mm的打印速度,150微米層高度,“噴嘴”直徑0.075mm。在OpenSLSGitHub的PA650Slic3r簡(jiǎn)介查看更詳細(xì)的工藝參數(shù)。這個(gè)功率水平很低,明顯的CO2激光器可以發(fā)射更大功率。最重要的是尼龍?jiān)?0.6μm的CO2氣體激光器的波長(zhǎng)下有更高的吸收效率。低成本,高功率二極管激光器在近紅外范圍808nm和840nm之間,不容易被尼龍吸收并轉(zhuǎn)化為熱能。在藍(lán)色范圍內(nèi)的激光可能有更好的吸收效率。增加能量吸收色素,如在上面的小燭樹蠟與碳的混合,用激光二極管實(shí)現(xiàn)應(yīng)該是可行的。PA650particlesizeandshapedistribution.PA650粒子的尺寸和形狀分布。Taulman618sparticlesizeandshapeafterpassagethrougha60meshsieve.Taulman618s大小和形狀的顆粒通過60目篩后。PA650sinteredin150micronlayers.PA650燒結(jié)在150微米層。Taulman618ssinteredin150micronlayers.Taulman618s150微米層燒結(jié)。ThePA650ringdemonstratesreasonablefinefeatureresolution.PA650戒指演示細(xì)微特征和精度。TheTaulman618sringhasslightlythickerfeatures,butthislikelyisaresultofthecoarsergrainsizeofthepowder.Taulman的618s戒指有略厚的特點(diǎn),但這可能是由于粗粒度的粉末。ThefinallayerofthefirstPA650printwithoptimizedparameters.第一個(gè)PA650參數(shù)優(yōu)化打印的最后一層。Thering(designedbyNervousSystem)aftermostofthepowderhadbeencleared.粉末被清除后的戒指(由神經(jīng)系統(tǒng)設(shè)計(jì))。Theringafterthoroughpowderremovalwithcompressedair.用壓縮空氣徹底除粉后的戒指。Theengineblock.發(fā)動(dòng)機(jī)缸體。Silica/Sand石英砂Thesilicaparticlessintertogetherincrediblysmoothly,ascanbeseenabove,withun-sinteredparticlesintheupperrightandfusedparticlesintehlowerleft.二氧化硅顆粒燒結(jié)在一起非常順利,從上可以看出,在右上方的未燒結(jié)顆粒和熔融顆粒在左下角。Silicasandshowspromiseasacheapandabundantprintmaterial.AsdemonstratedbyMarkusKayser,sandcanbethermallyfusedintoobjectsofsomefunctionality.Furtherexplorationbeyondthissimpletestofsinterabilityisnecessary.石英砂是一種很有前景的廉價(jià)和豐富的印刷材料。由MarkusKayser表明,砂可熱融合到一些功能對(duì)象。進(jìn)一步探索如何優(yōu)化這個(gè)簡(jiǎn)單的燒結(jié)性能測(cè)試是必要的。Sucrose蔗糖Detailoflaser-meltedcrystallinesucrose.詳細(xì)的激光熔化結(jié)晶蔗糖。Meltedregionathighermagnification.高倍鏡下區(qū)域熔化。Sucrosehasatendencytobothballandcaramelize.蔗糖熔融有一個(gè)趨勢(shì)——球和焦糖都有可能。Sucrosee

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