arcam’s electron beam melting (ebm)
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M f t db A I ti S dManufacturedbyArcamIncorporation,Sweden
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Introduction to EBMIntroduction to EBMEBM is one form of high energy beam used for
l imetal processing.Basically EBM is a thermal process.Due to the various facilities provided with the Due to the various facilities provided with the
system, EBM becomes a versatile process for various precision and micro manufacturing applications. The system hassystem has
capability to vary the current density.provision of energy in Pulsed form besides Continuous mode.very fine focusing system to a longer focal length as compared to its competitor i.e. laser beam.
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Electron Beam Generation
1 A th d ti1. A cathode section generates an electron beam.beam.
2. An anode section accelerates the beam.
3. The magnetic lens converges and deflects the electron beam to the desired position.
Scheme of Electron Beam Machining Process
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Scheme of Electron-Beam Machining Process
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Electron Beam Set-uppThe rate at which electrons are emitted from a hot surface by thermo-ionic emission is given by
I = C 2 exp(-/)where I is in amp/cm2, is the p ,absolute temperature, C is a constant, and is given by = e/(k)with e = charge of an electron, k = Boltzmans constant and k = Boltzmans constant, and (when measured in electron-volts) = thermo-ionic work f ti
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function
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Electron Beam GenerationElectron Beam GenerationA tungsten wire filament in cathode is heated to produce electron beam by thermo-ionic emission.Electrons are accelerated to a speed of about 200,000 km/s (about 2/3 of Speed of light) with a voltage ofkm/s (about 2/3 of Speed of light) with a voltage of about 150 kV.The electron beam can be focused to 10 to 200 m to produce an energy-density of about 3500 GW/mm2.The focusing area of the electron beam can be
t ll d il b l t ti lcontrolled easily be electro-magnetic lenses.The electron beam can be maneuvered precisely and swiftly by magnets on the work-surface.swiftly by magnets on the work surface.A high vacuum minimizes the electron collision with air molecules and energy loss.
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Electron Beam in Ambient Air Electron Beam in Vacuum
In vacuum a clear stream of electrons bombarding the surface of a material, allowing an easy and predictable cut.
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Effect of Vacuum Electron Beam Propagation
Vacuum Levelacuu e e
(courtesy, Leybond-Heraeus Vacuum System, Inc)
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Analysis for High Voltage y g gand Vacuum
E f th l t it b ti th b t tEnergy of the electrons, on its absorption on the substrate, should be sufficient to cause thermal processing.
Energy means the kinetic energy of the electrons to reach its maximum velocity. y
This may be possible underunder high accelerating electric fieldunder magnetic field (however it may be used ford i ti f th l t f it i di ti )deviation of the electrons from its moving direction)under high vacuum to avoid resistance to the movingelectrons
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electrons
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Requirement for High VoltageRequirement for High VoltageThe electrons out of the cathode (having high potential( g g penergy) are accelerated under and electric field towards theanode. As it moves, it gains kinetic energy at the cost ofpotential energy.potential energy.
The sum totals energy of the electron at any point in its path: (m U 2) eE = C (meUe ) eEs C
where, me = Mass of an electron; Ue = velocity of the electron;e = Electron Charge; Es = Field strength and C = Constant.
At the cathode Es = 0 and Ue = 0; so C = 0 and (meUe2) = eEsUe = (2e/ me). Es km/sec
As me = 9.109 x 10-31 kg, and e = 1.602 x 10-19 coulombUe = 600Es km/sec
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So at about 150 kV, Vs = 230,000 km/sec
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The electron can be deflected by Magnetic field, which helps in focusing or deflect the beam of electrons due tohelps in focusing or deflect the beam of electrons due to Lorenz force.
So the beam can be deflected magnetically and canalsoalso
be focused to 10 to 200 micron and
attain an energy density of about 6500 GW/mm2
achieve good narrow cut or holeachieve good narrow cut or hole.
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Electron Beam Processing Mechanism The intensity of the beam is compromised by the collision
with air molecules. It is difficult to calculate the time and/or beam intensity of the irradiated stream hitting the surfacebeam intensity of the irradiated stream hitting the surface, required to cut the part or drill a hole.
= 2.6 x 10-17 (V2/ ), mmV = Accelerating potential, V = Density of material, kg/mm3
Drilling Steel by EBM operating at 150 kV:
= 2 6 10-17 [(150 103)/ (76 10-7)]2 mm = 77 m = 2.6 x 10-17 [(150 x 103)/ (76 x 10-7)]2 mm = 77m
The electron beam is shot through the vacuum towards the i l Th l f h h h lmaterial. The electrons often pass through the outer layer
of the material and then become trapped in the material. The dark line shows the path of the electron.
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Process parameters for electron beam machiningbeam machining
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Schematic of Arcams electron beam melting processbeam melting process
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TheEBMProcess Apowerfulelectrongun shootsout
highspeedelectrons.Thenbyusingelectromagnets,theelectronbeamisf d d h l
Themagazineofpowderscrapesoutathinlayerofmetalpowderinaverticallyadjustablecradle.Inthiscradlethebj illb d focusedandyetotherelectromagnetsare
usedtosteerthebeam.Whenthebeamhitsthemetalpowderitisheatedsomuchthatthemetalpowdermelts.
M t l d i f di t i th t
objectwillbecreated. Thefirstlayeroftheobjectiscreated
throughmeltingthelayerofmetalpowderwithacomputercontrolledl t b Th bj tf th Metalpowderisfedintoamagazinethat
ismountedintothemachine.Dependingontheuseoftheobject,anumberofdifferentmetalpowderscanbeusede g alloys
electronbeam.TheobjectfromtheCADmodelisbuiltlayerbylayeruntilacomplete,solid,metalproductiscreated.
Whentheruniscompletethecradlecanbeusede.g.alloys. Themachine,whichisusedduringthe
manufacturing,ispreparedfortherun.Thedoorisclosedandvacuum isinduced.Hightemperature maybe
Whentheruniscompletethecradlewiththeobjectinitspowderbeddingisbeingremovedfromthemachine.Thenitislefttocooloff.
Whentheobjecthascooleddown it'sg p ymaintained.
Whentheobjecthascooleddown,it sbeingcleanedfromexcessivepowderandtheslightlyrough metalobjectisreadyforthefinaltreatment.
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Different Modules of EBMDifferentModulesofEBMMachine ENCLOSURE
Themachinehasanenclosuretoprotectthesystemswithinthemachine.Theenclosureisalsofortheoperatorssafety.Theenclosureisconstructedinpaintedsheetmetalandh i d f h h b i d fh d d l dl d l thewindowforthevacuumchamberismadeofhardenedglassandleadglass.
VACUUMCHAMBERMadeof20mmstainlesssteel.ContinuouslyTIGweldedontheinsideforvacuumtightnessandintermittentlyTIGweldedontheoutsideforstrength ThechamberistightnessandintermittentlyTIGweldedontheoutsideforstrength.Thechamberisalsoreinforcedwithstruts.Connectionflangesofstandardtype.
VACUUMSYSTEMThevacuumsystemconsistsofoneturbopump260l/secandisbackedupbyoney p p p ymechanicalpumpwithacapacityof10m3/h.ThevacuumsystemiscontrolledviaaPLCwhichinturncommunicateswiththecontrolcomputer.
THEELECTRONGUNConsistsofthreeroundunits Thebottomunithasawater cooledbaseandcontainsConsistsofthreeroundunits.Thebottomunithasawatercooledbaseandcontainsthelenssystemforfocusingandcontrollingthebeam.Themiddleunitcontainstheanode.Thetopunitconsistsofhighvoltageconnection,filamentholder(cathode),controlelectrodeandsetscrews.
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DifferentModulesofEBMMachine THEHIGHVOLTAGEUNIT
Thehighvoltageunitiscontrolledfromthecontrolcomputer.
CONTROLSYSTEMCONTROLSYSTEMConsistofanindustrialcomputer(MicrosoftWindows2000Professional)whichinturncontrolsandchecksthevacuumsystem,thehighvoltageunits,theelectronbeamlenssystem,thefabricationtable,powderdosageandpowderplacement.
CONTROLPANELThecontrolpanelconsistsofabuiltinindustrialtype15"PCtouchscreen.Inaddition,anindustrialtypekeyboardisavailableonaslidingunitformorecomplexcommands.
THEBUILDINGTANKMadeofstainlesssteel,joinedwithscrewjoints.Thevolumeofthebuildingtankis250x250x200mm,WxDxH,whichgivesavolumeof12,5liter.Thebuildingtankhasaheightadjustablebottomplatewhichiscontrolledbyalineardevicedevice.
DOSAGEEQUIPMENTConsistsoftwopowdercontainers,welded,ofstainlesssteel.Twopowderdosageunitsandapowderdistributionunitwhichmoveshorizontallyacrossthefabricationtable
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andapowderdistributionunitwhichmoveshorizontallyacrossthefabricationtable.
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DifferentModulesofEBM
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EBMSpecificationsp
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Materials ToolSteel
L All S l LowAlloySteel AlloyedTitanium CommerciallyPureTitanium NickelAlloys Nextclassofmaterialstobedevelopedwillbealuminumalloy(s)forautomotiveandaerospaceapplications.
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MechanicalPropertiesp
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AdvantagesofEBMg ElectronBeamWelding has
becomeavitaltechnologyinmanyindustries Someofits
ElectronBeamMeltingbenefitsfromallofthesefactorsinthesameway Comparedwithmanyindustries.Someofits
benefits include: Abilitytoachieveahighenergy
levelinanarrowbeam.
inthesameway.Comparedwithlasersintering/meltingadditionalbenefits include:
Higherefficiencyingeneratinglevelinanarrowbeam. Vacuummeltqualitycanyield
highstrengthpropertiesofthematerial.
Higherefficiencyingeneratingthebeamofenergyresultinginlowerpowerconsumptionaswellaslowermaintenanceandi t ll ti t Vacuumenvironmenteliminates
impuritiessuchasoxidesandnitrides.
ld f
installationcosts Highactualoverallpower
resultinginhighbuildspeeds Deflectionofthebeamcan Permitsweldinginrefractory
metalsandcombinationsofdissimilarmetals
Deflectionofthebeamcanachievedwithoutmovingpartsresultinginhighscanningspeedandlowmaintenance.
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DisadvantagesofEBMg Requiresvacuumwhichaddsanothersystemonthemachinewhichcostmoneyandmustbethemachinewhichcostmoneyandmustbemaintained[Addedbenefit:Vacuumeliminatesimpuritiesandprovideandgoodthermalp p genvironmentforfreeformfabrication]
Electronbeamtechnologyproducesgammaraysgy p g ywhileinoperation[Solution:Thevacuumtankshieldstheraysperfectlyifproperlydesigned.]
Requireselectricallyconductivematerials[Comment:metalsareconductive]
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ApplicationsofEBMpp PresentR&Disfocusingonpartsforhighperformanceapplications
withinautomotive andaerospace industryaswellasbiomedicalapplicationssuchasimplants applicationssuchasimplants.
Typicalapplicationsarecomplexpartsmanufacturedinlowvolumeswherecastingandmachiningwouldrequiretoomuchofleadtime,machinetimeorscrappingofmaterial.machinetimeorscrappingofmaterial.
Thetechnologycanalsobeusedtomanufacturepartsfeaturinggeometriesthatcannotbeachievedinothermanufacturingtechnologies,thusprovidingsuperiorperformanceinthepartandg p g p p pvaluetothecustomer.Examplesofsuchapplicationsare:
Complexlattice/frameworkstructuresforlightweightdesign Internalcavitiesforlightweightdesign,weightdistributiong g g g
optimizationandflowcontrol Optimizationofmaterialandstressdistribution Conformalcoolingchannelsg
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Titaniumandsteelplatesfabricatedforrepair of bone fracturerepairofbonefracture
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EBM Fabricated exhaust coupling flange (Volvo), The component shown mounted for real-world
testing on the righttesting on the right
Steel test piece
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Volvo camshaft sensor coverVolvo camshaft sensor cover made of reinforced PBT by injection
molding.The cooling cycle for this part was
The shape of the conformal cooling channels within the moldg y p
reduced from 25 to 15 seconds using conformal cooling channels,
created as Arcams EBM
channels within the moldfor the Volvo part created in the normal course of the structural building process
technology made the core and cavity inserts.
g pfrom CAD to metal.
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