Crimp Tooling — Where Form Meets Function Quality, cost, and throughput are key attributes for any production process. The crimpterminationprocessisnoexception.Manyvariablescontributetotheresults. Crimp tooling, defined here as crimpers and anvils, is one of those variables. Thispaperwillfocusondefiningkeycharacteristicsofcrimptoolingandtheeffects thosecharacteristicsmayhaveontheproductionprocess. Introduction Quality,cost,andthroughputareassociatedwithspecificmeasurementsandlinkedtoprocessvariables.Crimp height,pulltestvalues,leadsperhour,andcrimpsymmetryaresomeofthemeasuresusedtomonitorproduction terminationprocesses. Manyvariablesaffecttheprocesssuchaswireandterminalquality,machinerepeatability,setupparameters,and operatorskill. Crimptoolingisasignificantcontributortotheoverallcrimpterminationprocess.Theconditionofcrimptoolingis constantlymonitoredinproductionbyvariousmeans.Thesemeansareoftenindirectmeasures.CrimpQuality Monitorsandcrimpcrosssectionsaremethodologiesthatinfertheconditionofthecrimptooling.Visualinspec- tionofthecrimptoolingcanbeused tocheckforgrossfailuressuchastoolbreakageortoolingdeformationwhichoccurredasaresultofamachine crash.Continuousmonitoringofproductionwillhelpdeterminewhen theprocessneedstobeadjustedandthereplacementofcrimptoolingcanbeoneoftheadjustmentsthatis made. Crimptoolingcanahavepositiveeffectonthequality,cost,andthroughputoftheterminationprocess.Highqual- itycrimptoolingcanproducehighqualitycrimpswithlessin-processvariationoveragreaternumberoftermina- tions. Itisdifficulttodistinguishcriticaltoolingattributeswithvisualinspectiononly.Someattributescannotbein- spectedevenbyrunningcrimpsamples.Thispaperwillpresentthereaderwithinformationthatidentifieskey crimptoolingattributesandtheeffectofthoseattributesonthecrimpingprocess. Key Crimp Tooling Characteristics Therearefourmajorcategoriesofkeycharacteristicsforcrimptooling.Theseare: • Geometryandassociatedtolerances • Materials • Surfacecondition • Surfacetreatment Eachofthesecategoriescontributestotheoverallperformanceoftheproductionterminationprocess. tooling.te.com

Geometry and Associated Tolerances Terminalsaredesignedtoperformtospecificationonlywhenthefinalcrimpformiswithinanarrowrangeof dimensions.Controllingcriticalcrimpdimensionsisinfluencedbymanyfactorsincluding: • Wiresizeandmaterialvariation • Terminalsizeandmaterialvariation • Equipmentcondition Thefinalqualityandconsistencyofacrimpcanneverbeanybetterthanthe qualityandconsistencyofthetoolingthatisused.Ifothervariationscould beeliminated,toolingcanandshouldbeabletoproducecrimpformsthat arewellwithinspecifiedtolerances.Inaddition,variationfromonetooling settoanothershouldbeheldtoaminimum.Crimptoolingfeaturesthatare wellcontrolledandexhibitexcellentconsistencyfromtoolingsettotooling setcanresultinshortersetuptimeaswellasmoreconsistentproductionre- sults. Somecriticalcrimpcharacteristicsaredirectlydefinedbythetoolingform andareobvious.Theseinclude: CrossSectionDefiningCrimpWidth, • Crimpwidth CrimpHeight,andFlash • Crimplength Othercriticalcrimpcharacteristicscanberelatedtoseveraltoolingformfea- turesand/orothersystemfactors.Thesemay belessobviousandinclude: • Flash • Roll,twist,andside-to-sidebend • Up/downbend • Crimpsymmetry • Bellmouth Thefollowingdiscussionfocusesontwocharacteristics,crimpwidthandflash,asexamplesofhowtoolingcan affectcrimpform.Similarargumentscanbeappliedtotheothers. Crimp Width Crimpwidthisagoodexampleofafeaturethatshouldbeconsistentandincontrolbetweendifferent crimpersofthesamepartnumber.Thereasonforthisisquitestraightforward.Foragiventerminalandwire combination,itisnecessarytoachieveanareaindex,AI,whichisdeterminedbytheterminaldesignerforop- timalmechanicalandelectricalperformance.Crimpheight,CH,andcrimpwidth,CW,directlyaffectachieving properAI.Areaindex,AI(asapercentage),isdefinedas: whereAtisthetotalareaofthewireandbarrelaftercrimping.A andA are,respectively,theinitialcross- W B sectionalareasofthewireandbarrelbeforecrimping.

AtypicaldesignpointforAIis80%.Inordertomaintain CrossSectionsShowingMin- thesameAI,thecrimpheight,CH,needstochangein- (a) imum(a)andMaximum(b) verselytothechangeofcrimpwidth,CW,inapproxi- AreaIndexperTerminal matelythesameproportion.Thus,iftheCWincreases Specification—aVariationof +2%,theCHneedstochangeapproximately-2%inorder ±3.5% toachievethesameAIdesignpoint.Atfirstglancethat maynotseemsignificant,butinrealityitcanbevery significant.Usinganothergeneralindustrydesignruleof (b) theratioofCHtoCWofapproximately65%,atypical setofdimensionsusedasanexamplemaybe:CW=0.110in, CH=0.068in Therefore,varyingtheCWby2%wouldresultinaCHvariationof2%,or0.0014in. AtaCHtoleranceof±0.002in,35%ofthetotalCHtolerancewouldbeusedbya 2%variationinCW.Thus,theimportanceofcrimpwidthcontrolisobviouswhen toolingischangedduringaproductionrun. Flash Mostcrimpterminationshavearequirementtolimitflash.Flashisdefinedasthematerialwhichprotrudestothe sidesoftheterminaldownandalongtheanvil.Flashisnormalinthecrimpingprocessbutexcessiveflashisvery undesirable.Controllingflashrequiresabalanceofseveralgeometricfactors.Otherfactorsinfluencingflashare relatedtosurfacefinishandfriction,whichwillbediscussedlaterinthispaper. Adominantfactorincontrollingflashiscontrollingtheclearancebetweenthecrimperandanvilduringthecrimp process.Definingtheidealclearancecouldinitselfbeasimplematterwereitnotfortwofacts: • Inordertominimizeterminals’stickinginthecrimper,thesides ofthecrimperaretapered.Thustheclearancebetweenthe anvilandcrimpervariesthroughoutthestroke. • Crimperandanvilsetsaretypicallydesignedtoterminatetwo tofourwiresizes.Thiscreatesmultiplecrimpheights.Sincethe sidesofthecrimperaretaperedtominimizeterminalsticking, themaximumclearancepermittedwithoutcreatingflashmust beassignedtothemaximumcrimpheightspecifiedforthe toolingset.Inaddition,aminimalclearancemustbemaintained forthesmallestcrimpheightspecifiedbythetoolingsetto prohibitcontactbetweentheanvilandcrimper. Crimper-to-AnvilClearance=X+Y attheFinalCrimpHeight Crimpertoanvilclearanceisthusacombinationofcrimpwidth,crimperlegtaper, anvilwidth,andcrimpheight.Thecriticaldesignpointisatthelargestcrimp height.Thiscontributiontothegapisdirectlydependentondimensionalcontrol. Thefollowingisofferedasanexample: Nominalcondition:CH=0.073in, CW=0.110in Crimperlegtaper=3.0degree AnvilWidth=0.109in Nominalanviltocrimpertotalclearance=0.005in Theclearancecangrowrapidlywithsmallchangesto (a) Significantflashcanbegenerated thenominaldimensions: withexcessiveanviltocrimper CHremainsunchanged=0.073in clearance,asshownbynominal designcondition(a)and+0.003in Increaseincrimpwidth,CW,=0.0008in overnominalcondition(b) Increaseincrimperlegtaper=0.8degree Decreaseinanvilwidth=0.0008in Thetotalincreaseintotalclearanceisthiscase= (b) 0.0026in Thismorethana50%increaseinthenominaldesign clearance,whichcanresultinunacceptableflash(seeright). Dimensionalcontrolisclearlycritical.

Materials Thematerialselectionfortoolingiscritical.Thematerialmust beabletomeetthein-servicedemandsplacedonthetoolingcomponents.Thetwocriticaltoolingcomponents tobereviewedarethewirecrimperandtheanvil. Thewirecrimperandtheanvilhavedifferentfunctionaldemands.Bothhavetheneedtowithstandhighloadsand moderateshock.However,thewirecrimperisinfactanaggressiveformingtool.Itmustwithstandhighshear loadingthatisaresultoffrictionalloadsgeneratedastheterminalbarrelslidesalongthecrimpersurfacesinthe formingprocess,andthenastheterminalbarrelisplasticallydeformedandextrudedtocompletethetermination. Theanvilexperiencessomeofthesameconditionsbuttoamuchlowerlevelofseverity. Thewirecrimperandtheanvilcanbelikenedtoapunchanddieintheworldofmetalworking.Thematerialsused inpunchanddieapplicationshavebeenwelldocumented,alongwiththematerialselectionprocess.Theadded severityoftheaggressiveformingandtheterminalandwireextrusionduringcrimpingaddcomplexity tothematerialselection.Thematerialselectionprocessinvolves: • Strengthofmaterialswithemphasisontoughnessneededto withstandthemoderateshocksgeneratedduringcrimping • Wearresistancetomaintainform Inadditiontotheabovedesignconsiderations,thereexistsanotherphenomenonthatoccursduringcrimpingthat cansignificantlyshortentheuseablelifeofawirecrimper.Materialcanbetransferredfromtheterminalbarrelto thewirecrimper.Thismaterialbuildupcanresultinunacceptableterminations.Thecrimpedterminalsurfacescan actuallybedeformedbytheindentationsofthedepositedmaterial.Crimpdeformationmayresultduetoin- creasedfriction.Toolingwearcanbeacceleratedduetohighercrimpforces.Surfacetreatmentsthatminimize thismaterialtransferarecriticaltoextendedtoolinglife. Strength of Materials Crimpersandanvilsaredesignedtobeabletowithstandstressesthataretypicallyencounteredduringcrimping. Thebasicdesignoftoolingwithreferencetosizeandgeometryhasbeenwellanalyzedandgenerallystresses generatedduringcrimpingareabletobeaccommodated.However,therearealwaysdemandingapplicationsthat willtaxthedesigntoitsstresslimits.Inthosecases,geometryandmaterialmaydepartfromthestandarddesign. Theseexceptionsaredealtwithonaone-by-onebasisandwillnot bediscussedhere. Itistheuniquerequirementofstressandshockthatneedstobediscussed.Peakcrimploadsgofromzeroto maximuminlessthan40ms.Toolingneedstowithstandthisloadcycleatarateofgreaterthanoncepersecond. Severalclassesoftoolsteelsaresuitableandarewelldescribedinthematerialhandbooks.Itistheprocessingof thesematerialsthatcanmakeasignificantperformancedifference. Inordertowithstandtherapidloadingtoahighstressonarepeatedbasis,thesurfaceofthematerialmustmini- mizecracksandimperfectionsthatmaybegeneratedduringthemachiningand/orheattreatoperations.Itisim- portantthatgrainstructurebecontrolledinsizeandorientationtoachievemaximumandconsistentservicelife. Decarburizationofthesurfaceduringheattreatingmustbecontrolled.Heattreatingprocesscontrolsarecritical toreproducingtheoptimalsurface.Machiningprocessesmustalsobecontrolledtoavoidsurfacecrackingdueto excessiveheatgenerationduringoverlyaggressivematerialremoval.Likewise,localizedtemperingmayoccur, whichcansoftenmaterialbeyondtheeffectiverange. Thesevariationsinfinalmaterialandsurfaceconditionsarenotreadilydetectablewithavisualinspection.They canmanifestthemselvesduringserviceandresultinunacceptabletoolingperformance. Wear Resistance Wearisgenerallydescribedasthegradualdeteriorationofasurfacethroughuse.Severaltypesofwearexistand includeadhesive,abrasive,andpitting.Bydesign,thetoolingisabletowithstandnormalsurfaceloads.Thus,pit- tingistypicallynotanissue. Theprimarywearmodeexperiencedbycrimptoolingisadhesivewear.Adhesivewearoccursastwosurfaces slideacrosseachother.Underload,adhesion,sometimesreferredtoascoldwelding,canoccur.Weartakesplace atthelocalizedpointsofadhesionduetoshearanddeformation.Adhesionishighestatthepeaksofsurfacefin- ishbecausethatiswheretheloadisgreatest.Duringcrimping,theidealconditionsexistforadhesivewear.Thatis, • Highloadingduetocrimpforce • Slidingsurfacesduetocrimpformation,andterminaland wireextrusion

Wearwillgenerallymanifestitselfmoresignificantlyatedgesofasurface.However,adhesivewearisoftenob- servedoversubstantialareasofthetooling.Itisimportanttonoteherethatthewirecrimperisthecomponent mostsusceptibletoadhesivewear.Generally,adhesivewearwillbedirectlyrelatedtoloadandtotheamountof relativemovementbetweenthetwomaterials.Althoughtheanvilmayhaveequalloading,theamountofrelative movementbetweentheterminalandtoolingismanytimesmoreatthecrimperthanattheanvil.Theinsulation crimpertypicallyexperiencesloweradhesivewearbecausetheloadisreducedcomparedtothewirecrimpand therelativemovementislessthanthatofthewirecrimper,sincethereisnoterminalandwireextrusionatthein- sulationcrimp. Adhesivewearcanbecontrolledintheselectionofthematerial.Differentalloysexhibitbetterorworsewearproperties. Thesepropertiescanbemeasuredandarewelldocumented.Adhesivewear isinverselyproportionaltothehardnessofthematerial.Thus,theharderthematerial,thelessadhesivewear.Incrimp tooling,thereisoftenatradeoffthatismade.Inordertoachievehigherwearresistance,thematerialoftenexhibits lowertoughnessbycomposition,hardness,orboth.Thefinalmaterialselectionisoftenbasedonyearsofexperience. Onematerialmayhavehighwearcharacteristicsandlowertoughness,andbesuitableforasmallterminalsincethe marginofsafetyonstressishigh.Anotherterminalmaybelargeandthetoughnesscouldbeofmoreimportanceduea lowerstressdesignmargin.Theabilitytodesignandmanufacturecrimpersfromseveralmaterialswillenableoptimal materialselectionforaspecificapplication. Thefinalpropertythataffectsadhesivewearissurfacefinish.Asstatedearlier,adhesionishighestatthepeaksofthe surface.Thus,thesmootherthefinish,thelesssignificantthepeaksandthelesssignificanttheadhesion.Adhesivewear canbereducedwithalowersurfacefinish.Surfacefinishaffectsothercrimpingperformanceparameters.Thesearedis- cussedinthenextsection. Abrasioncanoccurdependingonterminalsurfaces.Ifaterminalisplatedwithanabrasivesubstance,thetooling couldsufferfromabrasivewear.Thiswouldbeanatypicalcondition andwouldbehandledbyspecialdesign. Otherapplicationswhereabrasivewearistheprimarywearmodeinvolveterminalsmadeofsteelandstainlesssteel. Extensivetestinghasshownchromiumplatingisthebestsurfacetreatmentthatcanbeusedoncrimpersdesignedfor theseabrasiveterminals. However, intheseapplications,crimperswillnotlastaslongasthosecrimpersusedtocrimp terminalsmadeofother,lessabrasivebasematerials.Usingalubricant(inthoseapplicationswherethisisacceptable) hasshowntoincreasethelifeofthecrimper. However,evenwhenlubricatedthecrimperlifecanbeexpectedtobe shorterwhencrimpingsteelorstainlesssteelterminals. Onceabrasivewearhastakenplacetothepointwherethechromiumplatinghasbeenremovedfromthebasetoolsteel ofthecrimper,assuccessivecrimpcyclesoccur,furtherwearwillhappenveryquickly. Withouttheprotective chromiumplating,theunderlyingsurfacewillthenbesubjecttoeitherfurtherabrasivewear,oradhesivewear. Forthis reason,careshouldbetakentoreplacethecrimperassoonaswearisvisibleonthesurfaceofthecrimper. Surface Condition Surfaceconditioncanaffecttheperformanceofthecrimptoolingaswellasthelongevityofservice.Asnotedin theprevioussection,ahard,smoothsurfacehasimprovedadhesivewearpropertiesand,thus,longerservicelife. Theotherattributethatneedstobeconsideredisfriction. Frictionisacontributingfactorindeterminingthefinal crimpformandprocesscharacteristics.Lowtoolingfriction resultsinlowercrimpingforceandthuscaninfluencecrimp formaswellastoolinglife.Consistentfrictionalcharacteris- ticsbetweentoolingsetswillresultinreducedprocess variation. Frictionofthecrimptoolingsurfacesisinfluencedbyfac- torssimilartothosethatinfluenceadhesivewear—hard- nessandsurfacefinish.Generally,hardermaterialsexhibit lowercoefficientsforslidingfriction.Frictioncoefficients havealsobeenshowntoberelatedtosurfacefinish.Manu- facturingprocessesneedtoproduceconsistentresults suchthatwhentoolingsetsneedtobechangedinproduc- tion,minimumdisruptionincrimpqualityisachieved.Ithas beenfoundthatmaintainingsurfacehardnessaboveRc55as wellaskeepingsurfacefinishesto8micro-inchesorlessis TypicalEffectofFrictiononCrimpForce desirabletoobtainconsistentcrimpresultsandminimize adhesivewear.

SurfaceTreatment Surfaceconditioncanaffecttheperformanceofthecrimptoolingaswellasthelongevityofservice.Asnotedinthe previoussection,ahard,smoothsurfacehasimprovedadhesivewearpropertiesand,thus,longerservicelife.The otherattributethatneedstobeconsideredisfriction. Acommonlyacceptedapproachtoimprovedcrimptoolingperformanceandlifehasbeentoapplyasurfacetreat- menttothecrimparea.Thewirecrimperhasbeendefinedinpreviousdiscussionsastoolingcomponentthatissub- jectedtotheseverestdutycycle.Thus,applyinganappropriatesurfacetreatmenttothewirecrimperwillhavethe mostbenefittocrimpperformanceandtoolinglife.Thesetreatmentscanincludehardmetalplatingorceramic coating. Anexampleofatreatmentthathasbeensuccessfulinachievingsignificantlevelofperformanceandlifeimprovements ishardchromiumplating.Thereareseveralvalidreasonsforthissuccess. First,chromiumplatinghasaverylowcoefficientoffriction.Asnoted,frictionhasasignificanteffectoncrimpform. Thestaticandslidingcoefficientsoffrictionforsteelonsteelaretypically0.30and0.20respectively.Chromiumplated steelonsteelcanreducethestaticandslidingcoefficientsto0.17and0.16. Thesecondareathatisgreatlyimprovedwith ChromiumPlatedCrimper chromiumplatingiswearresistance.Adhesivewear Surfaceafter100,000Termina- resistanceisimprovedassurfacehardnessimproves. tions.Notethereisnovisible ChromiumplatingtypicallyexhibitsahardnessRc buildupofmaterial. 65+.Thishardnesslevelgreatlyenhancesresistance toadhesivewear.Also,thisnowfreesupthedesigner toconsidermorebasemetaloptions.Abasematerial ofreducedwearresistancebutgreatertoughnesscan beselectedanditswearresistanceimprovedwith chromiumplating.Thus,chromiumplatingcanenable abettertoolingsolutionforthecrimpproduction UnplatedCrimperSurface process. after60,000Terminations. NoteSignificantbuildupof Third,andperhapsoneofthemostsignificanteffects material. ofchromiumplating,isitsresistancetoadhesionand coldwelding.Asideeffectofadhesivewearisthe GrossDeformationofCrimped transferofmaterialfromtheterminaltothewire TerminalResultingfromMate- crimper.Bydefinition,adhesiveweariscausedbyma- rialBuildupinCrimper terialadheringtolocalizedpointsonthesurface. Someoftheadhesionresultsinthesurfacematerial beingwornawayandsomeinthetransferofmaterial fromtheterminaltothecrimper.Asmorecycles occur,morematerialistransferred.Thusthereare- sultantbuildupofterminalmaterialonthecrimper. Thisbuildupwillresultintwopotentiallycatastrophic VisibleDeformationofOuter failures: CrimpSurfaceasaresultofIn- • Thebuilt-upmaterialwillcreatedeformationsin dentationfromMaterialBuildup onCrimper theterminal surface,resultinginunacceptable crimps. • Crimpswillbegreatlydistortedduetosignificantchangesinthefrictionfactorandresultintheterminalsnot conformingtothedesiredform.Unacceptablecrimpforms,suchasunsymmetricalcross-section,excessive flash,andopenbarrelscanresult. Chromiumplatinghastheabilitytobeapplieduniformlyandconsistentlyandexhibitsexcellentadhesiontothe basemetals.Theuniquebenefitsofchromiumplating,suchaseaseofapplication,consistencyofplating,adhe- siontobasemetal,extremelylowcoefficientoffriction,veryhighhardness,andresistancetoadhesion,makeit trulydifficulttomatchincrimpperformanceanddurability.Howevermanyalternativecoatingsarebeingat- tempted,andsomeshowexcellentpromiseinspecificapplications. Summary Thispaperhasexploredfourcategoriesofcharacteristicsthatarekeytohighperformancetooling.Severalexam- pleshavebeendiscussedwhichdemonstratehowminorvariationsinthosecharacteristicscanhavemeasurable andsometimessignificanteffectsontheresultantcrimpformanditscompliancetospecifications.Thesesame characteristicscanaffecttoolingservicelife.Itisalsoalogicalextensionofthesediscussionstoconcludethat variationsofthesecharacteristicsfromonetoolingsettoanothertoolingsetcanaffectprocesscontrolwhen toolingchangesarerequiredinproduction.Maintainingprocesscontrolmayrequireadditionalsetuptime.Quality toolingthataddressesthekeycharacteristicsofgeometry,materials,surfacecondition,andsurfacetreatmentis animportantcomponentofyourtotalqualitycontrolprogram.

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