ARCAM’s Electron Beam Melting (EBM)

M f t db A I ti S dManufacturedbyArcamIncorporation,Sweden

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.

11/11/2013 P Saha IIT Kharagpur 2

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


Scheme of Electron-Beam Machining Process

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


function

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.


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.


Effect of Vacuum Electron Beam Propagation

Vacuum Levelacuu e e

(courtesy, Leybond-Heraeus Vacuum System, Inc)


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


electrons

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


So at about 150 kV, Vs = 230,000 km/sec

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.


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.


Process parameters for electron beam machiningbeam machining


Schematic of Arcams electron beam melting processbeam melting process


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.


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.


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


andapowderdistributionunitwhichmoveshorizontallyacrossthefabricationtable.

DifferentModulesofEBM


EBMSpecificationsp


Materials ToolSteel

L All S l LowAlloySteel AlloyedTitanium CommerciallyPureTitanium NickelAlloys Nextclassofmaterialstobedevelopedwillbealuminumalloy(s)forautomotiveandaerospaceapplications.


MechanicalPropertiesp


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.


DisadvantagesofEBMg Requiresvacuumwhichaddsanothersystemonthemachinewhichcostmoneyandmustbethemachinewhichcostmoneyandmustbemaintained[Addedbenefit:Vacuumeliminatesimpuritiesandprovideandgoodthermalp p genvironmentforfreeformfabrication]

Electronbeamtechnologyproducesgammaraysgy p g ywhileinoperation[Solution:Thevacuumtankshieldstheraysperfectlyifproperlydesigned.]

Requireselectricallyconductivematerials[Comment:metalsareconductive]


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


Titaniumandsteelplatesfabricatedforrepair of bone fracturerepairofbonefracture


EBM Fabricated exhaust coupling flange (Volvo), The component shown mounted for real-world

testing on the righttesting on the right

Steel test piece


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.


ARCAM’s Electron Beam Melting (EBM)

Documents