Milling Tutorial

8/6/2019 Milling Tutorial

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TexasTechUniversity

ElectricalEngineeringDepartment

IEEEStudentBranchMillingTutorial

AnEEsGuidetoUsingtheMillingMachine

Writtenby:JuanJoseChong

Photosby:DavidHawronsky

IEEE#:90499216

March24,2011

Rev.A


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ContentsTableofFigures............................................................................................................................................. 3

Introduction.................................................................................................................................................. 4

Whatismilling?............................................................................................................................................. 4

Whylearnhowtomill?................................................................................................................................. 4

Whatwillyouneedinordertomill?............................................................................................................ 4

CopperSubstrate...................................................................................................................................... 5

MillingBits................................................................................................................................................. 5

Tape........................................................................................................................................................... 6

HowtoMill.................................................................................................................................................... 6

DrillinganAlignmentHole........................................................................................................................ 6

TurningonandInitializingtheMachine................................................................................................... 7

PlacingCopperontheTable..................................................................................................................... 8

LoadingFiles,Mirroring,andIsolating...................................................................................................... 8

PlacingtheCircuit................................................................................................................................... 11

RunningLayers........................................................................................................................................ 12

DrillLayer................................................................................................................................................ 12

TopIsolationLayer.................................................................................................................................. 14

FlippingtheBoard................................................................................................................................... 15

CuttingOutYourDesign......................................................................................................................... 16

Cleanup................................................................................................................................................... 16


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TableofFiguresFigure1 OriginalCircuitBoardvs.MilledReplacementBoard................................................................... 4

Figure2 30Degree(Left)vs.60Degree(Right)Endmill............................................................................. 5

Figure3 DrillBit(Left)andRoutingBit(Right)........................................................................................... 6

Figure4 InitializingSelection...................................................................................................................... 7

Figure5 MaterialChangeButton................................................................................................................ 7

Figure6 CopperPlacedontheMachineTable........................................................................................... 8

Figure7 SelectingtoAutoDetectFiles....................................................................................................... 8

Figure8 DecimalSelection.......................................................................................................................... 9

Figure9 IsolateButton................................................................................................................................ 9

Figure10 IsolationWindow........................................................................................................................ 9

Figure11 IsolatedCircuit.......................................................................................................................... 10

Figure12 LayersButton............................................................................................................................ 10

Figure13 IsolationWindowwithMirroringEnabled................................................................................ 10

Figure14 SelectingLayoutforMoving..................................................................................................... 11

Figure15 JumptoCursor.......................................................................................................................... 12

Figure16 RunningaLayer......................................................................................................................... 12

Figure17 ToolChangeWindow................................................................................................................ 13

Figure18 CheckingDepthofaDrillBit..................................................................................................... 13

Figure19 MachineJogWindow................................................................................................................ 14

Figure20 IsolationDepthTesting............................................................................................................. 15

Figure21 CopperBoardFlipped180Degrees.......................................................................................... 15

Figure22 JumpingtoMirrorCursor......................................................................................................... 16


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IntroductionSoyouveprobablyheardpeopleinprojectlabaskingaboutmilling,andmaybehaveseenaboardor

twobefore,butneverknewexactlywhatitwas.Well,thisguideisjustforyou!ItswrittenbyanEE

student,forEEstudents!Ifyouhavedoubtsabouthowsomethingisdoneafterreadingthisguide,ask

upperclassmen.Itwillhelpeveryonetohaveapositivemillingexperience(andalsokeepyoufrombeing

theguywhobrokethemachine!)

Whatismilling?Millingistheprocessbywhichacircuitdesignisetchedintoacoppersubstratebymeansofa2axis

CNCmachine,orforusEEs,itsbasicallyawaytodesignandbuildcircuitsquicklyandeasily.Onceyou

understandhowtheprocedureworks,andwithabitofpractice,youcanhaveafullcircuitboardin

about20minutes!Thismethodmayalsobecomeyourpreferredmethodofprototypinginsteadofusing

protoboardorbreadboardswithbreakoutboards.

Figure1 OriginalCircuitBoardvs.MilledReplacementBoard

Whylearnhowtomill?Whilemillingisnotstrictlynecessaryfortheearlyprojectlabs(1&2),itisagoodideatogetyourfeet

wetandlearnhowitsdonebeforeitbecomesnecessaryinfuturelabs.Millingalsomakesitpossibleto

makemuchmorecomplicatedandcleanercircuitdesigns.

Millingopensthedoortosurfacemountpartswhicharenearlyimpossibletouseonprotoboardand

muchless,breadboards.MoreandmoremanufacturersaremovingfromDIP(throughhole)packagesto

muchsmallerandcheaperSMT(surfacemount)parts.Whilesolderingthesepartsmayrequiresome

morepractice,asstatedearlier,thesooneryoubeginworkingwiththesepartsandtools,theeasier

futureprojectswillbe.

Whatwillyouneedinordertomill?WhileTexasTechandtheEEdepartmentprovidethemachineandsoftwarenecessarytomill,youmust

providesometoolsyourself.


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CopperSubstrateThisoneisprettyessential;ifyoudonthavecoppertomillyourcircuitonto,youcantmill!The

substrateisbasicallytwothinpiecesofcoppergluedontoafiberglasssubstrate.Thissubstrateiscalled

adielectricandcanvaryinwidth,ascanthewidthofthecopper.IfyouredoingsomesortofVHF/UHF

projectwhereimpedancemustbepreciselycontrolled,youmusttakethesemeasurementsinto

account,butformostprojects,anycopperavailableinthestockroomshouldsuffice.

Itshouldalsobenotedthatsincethesubstrateistwoconductorsseparatedbyadielectric,itisbasically

acapacitor.Becauseofthis,youcanexpectslightlymorecapacitancebetweentraces.

MillingBitsAsmentionedearlier,thisprocessusesaspecialbitcalledanendmilltoseparatetracesfromtherestof

theplane.Therearemanytypesofendmillsavailable,buttypicalsizesareanythingfrom10to100mills

(1mill=1/1000inch). Youmayfindsomeendmillsaresoldin45,60,and90degreeincrementsaswell.

Thesemeasurementsspecifytheanglewhichtheendmillspointmakes.90degreeendmillscancut

tracesofabout16mills,45degreescancuttracesofabout12millsand45degreescancutabout6mill

tracesifyourecareful.Mostofthesebitscanbefoundonline.Theretailerwhichistypicallyusedis

http://www.precisebits.com

Thereisalsoanothersetofbitsthatisrequiredtomill.ThesebitsarecalleddrillbitsandareusedtodrillholesforIClegs,headermounts,VIAs,etc.Youmustusedifferentsizesofbitsinordertodrill

differentsizedholes.Ifyourcircuitrequiresacertainsizeofbit,itisimperativethatthepropersizebe

used.Ifthisruleisnotfollowed,theholesdrilledmayeitherbetoolargeortoosmallforyourpart.Too

small,andthepartwillnotfitintotheboard.Toolarge,andtherewillnotbeenoughofapadleftonthe

boardtosolderto.Typicalsizeswillrangefrom28to45mills.Thesebitsmaybepurchasedfromthe

previouslymentionedwebsite,orfromHarborFreightTools(34thandI27).

Figure2 30Degree(Left)vs.60Degree(Right)Endmill


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Thefinalsetofbitsareoptional,butwillmakecuttingoutthecompletedboardmucheasier.Thisbitis

calledaroutingbit(alsoknownasacutoutbit)becauseitwillcleanlycutoutthecompletedcircuitfromtherestofthecopper.SomeprefertouseacopperpressoraDremel,butIhavefoundthesebits

toproducethebestresults.

TapeTapewillberequiredinordertotemporarilyholdyourcopperboardtothemachineandsacrificiallayer

placedonthemachine.Silverducttapeistypicallyused,butmostothertypesoftapewillalsowork.

HowtoMillDrillinganAlignmentHoleFirstthingyouhavetodoisdrillanalignmentholeforyourcopperboard.Besuretomeasureexactly

themiddleoftheboardanddrillasshowninthefigure.Iftheholeyoudrillisoffbyevenatinybit,the

boardwillbeslightlyoffsetlateronintheprocessandwillnotlineupproperly.

Figure3 DrillBit(Left)andRoutingBit(Right)


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TurningonandInitializingtheMachineToturnonthemachine,firstflipthepowerswitchesonthethreemachinesnexttothemillingPC.Also

turnonthemillingPCifitisoff.Oncefinished,opentheprogramnamedIsoProonthedesktop.Thisis

theprogramwewillbeusingtocontrolthemillingmachine.

Thefirstthingtodoisinitializethemachine.Thisprocessresetsthemachineandletsthecomputer

knowwherethemachinesboundariesare.GotoMill>Initializetoinitializethemachine.Itshouldbegin

movingandonceitsfinished,itshouldstopatthefrontcenterofthetable,justabovethealignment

pin.InitializationmustbedoneeverytimeIsoProisstarted.

Figure4 InitializingSelection

Oncethemachineisfinished,anewbuttonlabeledMaterialChangeshouldbecomeactive.Clicking

thiswillcausethemachinetomovethemachinehead,orspindle,outoftheway,allowingyouto

replacematerialonthemachinetable.

Figure5 MaterialChangeButton


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PlacingCopperontheTableWiththespindleoutoftheway,makesurethetableiscleanandplaceyourcopperboardonit.Once

alignedwiththefaceofthemachineasshown,tapedowntheboard.2or3piecesoftapeshould

suffice.

Figure6 CopperPlacedontheMachineTable

LoadingFiles,Mirroring,andIsolatingThenextstepistoloadyourfilesintotheprogramandbeginpreparingthem.Inordertodothat,click

onFile>Import>AutoDetectFiles

Figure7 SelectingtoAutoDetectFiles


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IfyouareusingtheTTUMilling.camfilefromEagleCADorimportingfromOrCADyoumustselectthe

optionsshowninthefollowingfigure.Thissettingtellsthemachinehowmanydecimalplacesitshould

takeintoaccountwheninterpretingyourgerberfiles.Thecorrectsettingisfourintegerdigitsandfour

decimaldigits.

Figure8 DecimalSelection

Oncethemachineisfinishedimportingyourfiles,thenextstepistoisolateyourtraces.Isolationisthe

processofisolatingyourtracesfromtherestofthecopperboard.Todothis,clickontheIsolate

button,selectyourtopandbottomlayers,andtypeinthespacewhichyouwishtoisolate.

Figure9 IsolateButton

Formostapplications15millsisusuallymorethanenough,butifyouareworkingwithsurfacemount

componentsaslittleas6millsmightberequired.

Figure10 IsolationWindow


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Oncethecomputerfinishesisolating,youwillseethattheprogramhasdrawnlinesaroundyourtraces.

Theselinesarethepathsthatthespindlewilltakewhencuttingoutyourtraces.Besuretocheckfor

errorsorpartswhereisolationdidnotworkcorrectlyandadjustasneeded.

Figure11 IsolatedCircuit

Onceyouarehappywiththeresults,clickontheLayersbuttonandselectMirrornexttoyour

bottomandcutoutlayers(ifoneexists).Mirroringtheselayerswillmakethemachineinterpret

everythingproperlywhentheboardisflippedlateronintheprocess.Alsonotethatifyouareusinga

cutoutlayer,youmustalsochangeitstypefromComponenttoIsolationinadditiontomirroringit.

Figure12 LayersButton

Figure13 IsolationWindowwithMirroringEnabled


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PlacingtheCircuitThefinalthingtodobeforemillingistomakesurethatyourcircuitwillproperlyfitonthecopper

substrateyouhaveplacedonthemachine.Todothis,rightclickonanyofthelayerstotheleftand

selectEditAll.Afterdoingso,drawaboxaroundallyourtracesandcutoutlayer.Besuretoselect

everylayer.Youcanzoomoutifneeded.

Figure14 SelectingLayoutforMoving

Abitofguessworkisrequiredtogettheboardtofitproperlysometimes,butitisimportanttomake

surethattheboardisproperlypositionedforagoodcircuittobemilled.Onceplaced,rightclickonone

ofthecornersofyourlayoutandselectJumptoCursor.Themachinewillmovetothelocation

specified.Dothisfortheoppositecornerandmakesureyouhaveenoughspace.Keeprepeatingthis

processuntilyouresureyouhaveenough.


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Figure15 JumptoCursor

RunningLayersNowthateverythinghasbeenprepared,layersmustberun.Irecommendrunningyourdrilllayerfirstin

ordertoensurethatpadsdonotgetdamagedandalsotogiveyoureferencepointswhenmillingthe

restofthecircuit.

DrillLayerInordertorunthedrilllayer,rightclickonthelayertotheleftofthescreenandselectRunLayer.

Figure16 RunningaLayer

Youwillnoticethatthemachinewillmoveoffofthetableandisaskingforabit.Thisdialogwindowwill

askforaspecificbitanditwillalsoshowyouwhatthediameterofthebitshouldbe.Besuretogivethe

machineabitclosetothesizeitrequests!Ifyoudontdothis,youmaynothaveenoughofyourpads

lefttosolderto!Youcansafelyroundupordown1or2millsifyoudonthavetheexactmeasurement.


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Figure17 ToolChangeWindow

Thetoolshouldbesnug,butnotoverlytight.Besuretonotdropthetoolswheninsertingorremoving

them!Ifoneisdropped,itwillshatter!!

Onceyouveinsertedyourtoolintothemachine,youmustensurethatthespeediscorrect.Thespindlespeed(howfastthetoolspins)shouldread60,000RPM.Afeedrate(howfastthetoolcutstraces)of60in/minisokayfordrillingonly.Slowerspeedsshouldbeusedforeveryotherprocess.

Thelaststepbeforestartingischeckingdepth.Inordertodothis,presstheheadofthemachinedown

manuallyandcompareittotheedgeoftheboard.Thetoolshouldjustpenetratetheloweredgeofyour

copperboard.Toadjusttheheightofthebit,turntheknobonthemachineheadmarkedwitha+and .

Donotadjustthefournutstotheleftofthespindle!!Also,dontgotoodeepintothesacrificiallayeras

youmighthitthealuminumtableandshatterabit!

Figure18 CheckingDepthofaDrillBit


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Onceallthesepreparationsarecompleted,clickRunLayertobeginthedrillingprocess.Themachine

willstopandaskfordifferentsizebitsifyouusedtheminyourdesign.

TopIsolationLayerThenextthingwehavetorunistheisolationlayer.Inordertodothis,wemustonceagaincheckfor

depth.Theprocessisnearlyidenticaltothepreviousone,theonlydifferencebeingthatwehaveto

slowthefeedratetoabout14in/minwhilekeepingthespindlespeedat60,000RPM.Theslowerthe

feedratetheslowerthewearonyourtoolsandthemorepreciseyoucanbe,butthelongeritwilltake

tomill.

Thetoolshouldjustbarelycutthecoppersurface;justenoughforittocompletelycutthroughthe

copper,butnotdiveintothefiberglasssubstrate.Onceyouinsertyourtoolintothemachine,clickon

theJogbutton.Thisbuttonwillallowyoutocontrolthemachineheadmanuallyinorderadjustthebit

depth.Youcanmovethespindlewiththearrowkeysonthekeyboard.ClickingtheSpindleOnbutton

will

turn

on

the

spindle

and

Head

Down

will

lower

the

head

using

air,

just

as

if

you

were

running

the

layer.Irecommendturningonthespindlebeforeloweringtheheadbecauseitwillcauselessstresson

thetoolandkeepyoufrombreakingit.

Figure19 MachineJogWindow


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Figure20 IsolationDepthTesting

Oncethoseadjustmentsaremade,click"RunLayer"andsitbackwhileyourboardismade.Youshould

watchtheprocessabittomakesurethatthetooliscuttingenoughcopper.

FlippingtheBoardOncetheisolationlayerisfinishedrunning,clickthe"MaterialChange"buttonandfliptheboard180

degreesasshown.Youshouldflipitsothatthealignmentholeisstilloverthepegatthefrontofthe

machine.Tapetheboarddownjustasyoudidbefore.

Figure21 CopperBoardFlipped180Degrees


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Theprocessforrunningthebottomisolationlayershouldbeidenticaltothetop,withtheexceptionof

onestep.Wemustfirstmakesurethattheholeslineupproperlysothattheisolationdoesn'tcuttraces

incorrectly.Todothat,rightclickonthecenterofanyholeonyourschematicandselect"Jumpto

MirroredCursor".Thiswillforcethemachinetomovethespindletothatspecifichole.Dothiswitha

coupleholesonoppositeendsofyourcircuitandchecktomakesuretheylineup.Makeadjustmentsto

thetapeandcopperboardasneeded.

Figure22 JumpingtoMirrorCursor

Rememberthatdepthmustbecheckedonceagaininordertoensurethatyoudon'tbreakabit!The

processisthesameasbefore.Besuretocheckthesettingsandonceyouarereadytoproceed,click

"RunLayer".

CuttingOutYourDesignIftheTTUMilling.camfilewasusedinEagleCAD,itwillhaveacutoutlayerreadymadeforyou.Thislayer

willbegeneratedusingtheDimensionslayerinEagleCAD.Ifyouwouldliketocutoutyourdesign

usingthislayer,someminorchangeswillneedtobemadeforittowork.Ifyouhavefollowedthis

tutorial,youshouldhavealreadychangedthelayertypefromComponenttoIsolationandmirrored

it.Ifyouarenotsure,gobackintotheLayerswindowanddoublecheck.

Onceyouarefinished,rightclickonthecutoutlayer,select"RunLayer",insertyourcutouttool,and

adjustthedepth.Itshouldbeaboutthesameusedfordrilling.Besurethatthespindlespeedis60,000

RPMandthefeedrateisabout12in/min.

CleanupOncefinished,removeyourtool,clicktheChangeMaterialbuttontogiveyouenoughspaceto

removeyourcopperboardandyourcircuit,sweepoffanyexcessdust,closetheprogram,andturnoff

alldevices.

Congratulations!You'vejustfinishedmillingaboard!

Milling Tutorial

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