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TRANSCRIPT
SPECIALTY CHEMICALS AND ENGINEERED MATERIALS
EDM GraphiteSelection guide
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Aerospace Applications
• Blades
• Vanes
• SealSlots
Consumer Applications
• CapsandClosures
• PlasticInjection
• ElectricalConnectors
Automotive Applications
• Speakers
• Lenses
• PowerDistribution
Medical Applications
• SurgicalFasteners
• DentalImplants
• OrthopedicJoints
7.92
mm
(0.3
12”)
APPLICATIONS—OurEDMelectrodematerialsofferthebestbalanceofmetalremovalrates,lowelectrodewear,andexcellent
totalcostofownership.EachEDMgraphitegradeprovidesconsistentperformancefromblocktoblock,
yeartoyear,andhasbeentailoredforaspecificrangeofelectrodeapplicationswithbenchmarkedperfor-
mancecharacteristics.
3
KEY FACTORS OF ELECTRODE SELECTION—EDMhastakenitsplaceasaproven,precision
technology,chosenforwhatitcando,ratherthan
whatconventionalmachiningcannotdo.EDM
machinetechnologyhasspawnedaworldofnew
applicationswhereinincreasedimportanceis
placedonthegraphiteelectrodematerialutilized.
Whiletherearemanymethodsusedtodetermine
therightmaterialforajob,webelievetherearefive
factorsthatmeanthedifferencebetweensuccess
andfailure,profitandloss.
Metal Removal Rate (MRR)
Metalremovalrateisusuallyexpressedascubic
millimetersperhour(mm3/hr)orcubicinchesper
hour(in3/hr),butinfactcouldjustasrealisticallybe
expressedas$/hr.AchievinganefficientMRRisnot
simplyamatteroftherightmachinesettings.Italso
involvesdirectenergydissipatedintheEDMprocess.
Graphiteisgenerallymuchmoreefficientthan
metallicelectrodes,howevermetalremovalrates
varywidelybetweengraphitetypes.Withtheproper
electrodematerial/workmetal/applicationcombina-
tion,MRRcanbemaximized.
Wear Resistance (WR)
Therearefourtypesofwear:volumetric,corner,end,
andside.Ofthefour,webelievethatcornerwearis
themostimportantsincethecontoursofthefinalcut
aredeterminedbytheelectrode’sabilitytoresistthe
erosionofitscornersandedges.Itfollowsthatifan
electrodecansuccessfullyresisterosionatitsmost
vulnerablepoints,thenoverallwearwillbeminimized,
andmaximumelectrodelifeachieved.Electrode
erosioncannotbeprevented,butitcanbeminimized
bychoosingtheproperelectrodematerial/workmetal
combinationandmachiningattheoptimumsettings.
Theabilityofanelectrodetoproduceandmaintain
detailisdirectlyrelatedtoitsresistancetowearand
itsmachinability.Minimizingcornerwearrequires
choosinganelectrodematerialthatcombineshigh
strengthwithhightemperatureresistance.
Surface Finish (SF)
Finesurfacefinishisobtainedbyacombinationof
theproperelectrodematerial,goodflushingcondi-
tions,andtheproperpowersupplysettings.High
frequency,lowpower,andorbitingproducethe
bestfinish,astheseconditionsproducesmaller,less
definedcratersintheworkmetal.Thefinalsurface
finishwillbeamirrorimageoftheelectrode’ssurface,
soAngstrofineandUltrafineparticle,highstrength
graphitesarethebestchoicesforfinishingelectrodes.
Machinability
Anymachinistwhohasevermachinedgraphiteis
awarethatgraphitecutsveryeasily.Simplybeingeasy
tomachinedoesnotnecessarilymakeamaterialthe
bestchoiceforanelectrode.Itmustalsobestrongto
resistdamagefromhandlingandfromtheEDMprocess
itself.Strengthandsmallparticlesizeareimportant
sothatminimumradiiandclosetolerancesmaybe
achieved.Materialhardnessisalsoafactoringraphite
machinability.Harderelectrodematerialswillbemore
pronetochippingduringthemachiningprocess.
Material Cost
Electrodematerialcostgenerallyrepresentsonlya
smallpartofthetotalEDMjobcost.Whatistoooften
overlooked,however,isthatelectrodematerialcost
consideredoutsidethetotaljobcostiscompletely
meaningless.
Fabricationtime,cuttingtime,labor,andelectrodewear
alldependontheelectrodematerialmorethanon
anyotherfactor.Thusitiscriticalthatyouknowthe
propertiesandperformancecharacteristicsofthe
availableelectrodematerialsastheyaffectthework
metalsyouaremachining.Onlywiththisdataisit
possibletomakeacost/performanceanalysisto
determinethetruecostofanEDMjob.
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EDM-AF5®graphite
EDM-AF5isthepremier
graphiteelectrode
materialavailableonthe
markettodaywithan
averageparticlesizeof
lessthanonemicron.
Thisparticlestructure
hassuperiorstrength,
providesforfinesurfacefinish(7μinRa),and
givesexcellentmetalremovalrateandhigh
resistancetowear.
TypicalValue
Average particle size:
<1 µm
Flexural strength:
1,019 kg/cm2 (14,500 psi)
Compressive strength:
1,554 kg/cm2 (22,100 psi)
Hardness: 83 Shore
Electrical resistivity:
21.6 µΩm (850 µΩin)
Applications
• Finedetailedelectrodesforengraving
• Hardtomachinedetail
• Delicateandfragileelectrodes
• Varioustypethreadingelectrodes
• Jobsrequiringfinesurfacefinishes
• Intricatemoldsanddies
GRAPHITE GRADES—
EDM-C3®graphite
EDM-C3isahigh-quality
graphiteinfiltratedwith
copper,recommended
wherespeed,wear,
andsurfacefinishare
important.Unequalled
forfragileelectrodes,
manyEDMerschoose
thisgradetocompensateforoperator
inexperienceorwherepoorflushingcondi-
tionsexists.
TypicalValue
Average particle size:
<5 µm
Flexural strength:
1,427 kg/cm2 (20,300 psi)
Compressive strength:
1,993 kg/cm2 (28,350 psi)
Hardness: 66 Shore
Electrical resistivity:
3.2 µΩm (127 µΩin)
Applications
• Finedetailedelectrodeswherestrengthiscritical
• Threadingelectrodes
• Aerospaceapplications
• Plasticinjectionmolds
• Machiningofcarbide
• Smallholedrilling
Copper Ultrafine
Our 5 micron EDM material Competitor’s 5 micron material
Angstrofine Graphite
5
EDM-3®graphite
EDM-3isanisotropic
Ultrafinegraingraphite
thatoffershighstrength
withoutstandingwearand
finesurfacefinishcharac-
teristicseasilymachined
tothicknessesof0.1mm
orless.
TypicalValue
Average particle size:
<5 µm
Flexural strength:
935 kg/cm2 (13,300 psi)
Compressive strength:
1,273 kg/cm2 (18,100 psi)
Hardness: 73 Shore
Electrical resistivity:
15.6 µΩm (615 µΩin)
Applications
• EDMingoffinedetailedelectrodes
• Punchanddiesets
• Plasticinjectionmolds
• Threadingelectrodes
• Useinaerospacemetalcutting
EDM-2®graphite
EDM-2isanisotropic
Ultrafinegraingraphite
withhighstrengthand
goodwearcharacteris-
tics.Recommendedfor
useondetailedelec-
trodes,wherespeed,fine
finish,andresistanceto
weararedesired.
TypicalValue
Average particle size:
<5 microns
Flexural strength:
787 kg/cm2 (11,200 psi)
Compressive strength:
1,188 kg/cm2 (16,900 psi)
Hardness: 71 Shore
Electrical resistivity:
16.0 µΩm (620 µΩin)
Applications
• ICMolds
• Aerospaceapplications
• Fine-detailedelectrodes
• Minimum-taper-cavities
• Blindcavitywork
Ultrafine Graphite
EDM-4®graphite
EDM-4isthepremier
offeringintheUltrafine
grainclassification.This
highlyisotropicgrade
combinesextraordinary
strengthwithmoderate
hardness,yieldingsuper-
iorelectrodefabrication
characteristics.EDM-4hassuperiorEDM
performancecharacteristicsformetalremoval
rates,wearandsurfacefinish.
TypicalValue
Average particle size:
<4 µm
Flexural strength:
1,230 kg/cm2 (17,500 psi)
Compressive strength:
1,511 kg/cm2 (21,500 psi)
Hardness: 76 Shore
Electrical resistivity:
12.7 µΩm (500 µΩin)
Applications
• EDMingoffinedetailedelectrodesrequiringexcellentsurfacefinishes
• Wirecutelectrodes
• Plasticinjectionmolds
Ultrafine Graphite
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EDM-200®graphite
EDM-200isanisotropic
Superfineparticlegraphite
providinggoodstrength,
surfacefinish,andwear
resistance.Moderately
priced,EDM-200graphite
providesexcellentrepeat-
abilityfromelectrodeto
electrodeandfromjob
tojob.
EDM-C200®graphite
EDM-C200isaSuperfine
graphiteinfiltratedwith
copperthatoffersexcel-
lentmetalremovalrates
andgoodwearresistance.
EDM-C200graphite
improvescuttingstability
inpoorflushingcondi-
tions,andisanexcellentmaterialforcutting
aerospacealloys.
TypicalValue
Average particle size:
10 µm
Flexural strength:
635 kg/cm2 (9,000 psi)
Compressive strength:
1,075 kg/cm2 (15,500 psi)
Hardness: 68 Shore
Electrical resistivity:
14.7 µΩm (580 µΩin)
TypicalValue
Average particle size:
10 µm
Flexural strength:
851 kg/cm2 (12,100 psi)
Compressive strength:
1,631 kg/cm2 (23,200 psi)
Hardness: 62 Shore
Electrical resistivity:
2.9 µΩm (114 µΩin)
Applications
• Structuralribs
• Roughingorfinishingelectrodes
• Largefeaturedmold
• Highstrengthlargeelectrodes
Applications
• EDMingoffinedetailedelectrodesrequiringexcellentsurfacefinishes
• Wirecutelectrodes
• Plasticinjectionmolds
Superfine Graphite
Copper Superfine
EDM-1®graphite
EDM-1graphiteisour
lowestpricedUltrafine
graingraphite.Inaddition
toprovidinggoodwear
resistance,speed,and
finish,lowerelectrode
fabricationcostsare
possiblewhenlarger
electrodesarerequired.
TypicalValue
Average particle size:
<5 µm
Flexural strength:
682 kg/cm2 (9,700 psi)
Compressive strength:
988 kg/cm2 (14,200 psi)
Hardness: 69 Shore
Electrical resistivity:
19.3 µΩm (760 µΩin)
Applications
• Fabricatingelectrodeswithgooddetail
• Lowwearelectrodes
• Highdetailroughingelectrodes
• Moldsanddies
7
TECHNICAL ARTICLES—AllarticlescanbeaccessedbyscanningtheQRcode
orvisitingusatpoco.com.
Total Cost of Ownership
TheTotalCostofOwnership
(TCO)modelandanalysis
arecommonlyusedtomake
decisionswhenpurchasing
newequipment,butcan
alsobeappliedtothemajor
elementsassociatedwiththe
operationofthesinkerEDM
equipment,suchasgraphiteelectrodematerials.When
TCOprincipalsareappliedtothesemajorelements,
thevaluepropositionandproductivityofthese
elementsstarttoimpactprofitabilityofowningand
operatingtheequipment.
Thisarticleprovidesinsightintothekey
aspectsofapplyingtheTotalCostof
OwnershipModeltoyourelectrode
materialselectionprocess,andusing
thismethodtomaximizetheefficiency
ofyourEDMprocess.
Dealing with Graphite Dust
Dust,acommonhouseholdwordthat
canbedefinedasafinelypowdered
substanceofvariousmattersoften
suspendedintheair.Thisarticlereviews
thecharacteristicsofgraphitedustand
answersoften-askedquestionsin
dealingwithit.
Making EDM Profitable
Thisarticlereviewsthefactorstocon-
siderwhenworkingwithanexotic
workmetalapplication,andareal-world
exampleofhowelectrodematerial
selectionandEDMparameterscan
impactthebottomline.
Electrode Effect on Quality EDM Finish
Thisarticlediscussestheeconomic
impacttheelectrodematerialhason
producingfinesurfacefinisheseven
withthenewerEDMgeneratortechnol-
ogy.Toaccessmoreinformationabout
howthequalityofyourelectrodematerialcanimpact
yourworkpiecefinish,scantheQRcodetoaccess
thefullarticle.
EDM Effect on Surface Integrity
Learnaboutthealteredmetallayers
createdduringtheEDMprocess,and
howtheEDMprocessparameters
canimpacttheworkpiecefinishand
surfaceintegrity.
Sometimes Graphite Isn’t Enough
Anexplanationofhowthecorrect
machineparameterscanimprove
yourEDMprocesswhendealing
withnon-standardmaterials,such
asberylliumcopper,titanium,and
tungstencarbide.
Graphite vs. Copper
Viewatruecostcomparisonoftime
andmaterialbetweencopperand
graphiteelectrodes,andexaminethe
differencesbetweeneachoftheEDM
keyperformanceindicators.Scanthe
QRcodetoreadthefullarticleandto
learnmoreaboutcopperversusgraphite.
EDM Graphite Buyer’s Guide
Unlessyouhavemoneytoburn,time
tospare,andagreatmoldrepairteam,
neverbuyEDMgraphitedescribedas
“equivalentto”or“asgoodas.”Learn
tipsonhowtoassureyouaregetting
whatyouneedwhenitcomesto
sourcinggraphite.
Apply
Justify
Compare Data
Benchmark
Calculate Results
Measure Process
Simulate Procedures
FOR MORE INFORMATION
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TECHNICAL ASSISTANCE—Ifyouhaveaquestionconcerningelectrodemateri-
als(oursoranyoneelses),calltheEDMexperts.Our
EDMtechnicalservicepersonnelhavemanyyears
ofpracticalEDMexperienceandcanhelpyou
withdesign,machining,operatingparameters,or
practicallyanysituationinvolvingelectrodeman-
agementtechniques.
• Gradeverification
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INDUSTRY-LEADING EDM TRAINING—WeofferanEDMtechnicaltrainingprogramto
helpEDMersimprovetheirperformance.Thisisa
no-charge,three-daytrainingsessionthatincludes
classroomandlaboratoryactivities,andprovidesa
betterunderstandingofhowtocontroltheEDM
processtoachievepredictableresults.Thisis
practicalinformationthattheattendeecanput
touseontheshopfloor.
• EDMbasics
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EDM TECHNICAL MANUAL—OurEDM Technical Manualisnowavailableonlineat
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