机械毕业设计英文外文翻译金刚石刀具磨损的评价.docx

机械毕业设计英文外文翻译金刚石刀具磨损的评价.docx

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机械毕业设计英文外文翻译金刚石刀具磨损的评价

Evaluationofdiamondtoolwear

W.Polini·S.Turchetta

Received:

28May2003/Accepted:

9January2004/Publishedonline:

19May2004

?

Springer-VerlagLondonLimited2004

W.Polini·S.Turchetta（u）

DipartimentodiIngegneriaIndustriale,

UniversitàdiCassino,

viaG.diBiasio43,03043Cassino,

ItalyE-mail:

turchetta@unicas.it

-0776-*******

Abstract

Thepresentstudyproposesatestprotocolregardingthewearofsintereddiamondtools.Asetofparameterswhichcharacterisethegradeofwear,anditsrelationshipwiththecuttingabilityoftheexaminedtools,areestablished.Theproposedprotocolestablishestheprocedureandtheequipmentforcarryingoutthetests,thefeaturesofthematerialstouseandtheformatofthereporttopresenttheresultsobtained.Thedevelopedtestprotocolindicatesanuniversallyapplicablewayformeasurementofthewearofthediamondtool.Itisanindispensableinstrumentforcorrectlycarryingouttheweartestsandforreliablyinterpretingtheresults.Theprotocoldevelopedsofarmainlyregardslaboratorytests,consideringtheslownessandprecisionofthemeasurementsinvolved.Giventhetotalabsenceofnorms,thisprotocolcouldbeabsorbedbynationalandinternationalnormestablishingorganisations.Thisprotocolhasalsobeenappliedtotwotypesoftoolsandtheresultsobtainedhaveappearedreliableandreplicable.Thetestprotocolproposedinthisstudymakesitpossibletoovercomethedifficultiesconnectedtothescarcityoftechnicaldataregardingthepropertiesofthetool,whichistypicalinthisfieldsincetherecipesfortoolmanufacturingarepatented.

KeywordsCuttingtool·Diamondsinteredmill·

Macro-geometricwearparameters·Testprotocol·Wear

1Introduction

Theincreasingdemandbothintheindustrialfieldandinurbanfurnishingforelementsinnaturalstonewithincreasinglycomplexgeometrymakesitnecessarytouseincreasinglyflexible

andautomaticmachines,suchasnumericallycontrolledmachiningcentres.Thesecentresmakeitpossibletocarryoutlargenumbersofoperationsbymeansofdiamondmills.Nostudiesonoptimisationofthecuttingprocesshavebeencarriedoutforthesejobs.Therefore,untilnow,asometimesimperfectsolutionhasbeenaccepted[1,2].Optimisationmeansreducingmachiningcostsand/ortimesand/orimprovingthequalityoftheproductsobtainedbyworkingondifferentfactors,suchascuttingstrengths,toolproperties,processtemperaturesandvibrations[3–5].Acriticalpointistheactualtool.Optimisationofthetoolpropertiesinrelationtothewearprocessleadstooptimisationofthewholeprocess.Thepresentstudyaimsatunderstandingthediamondtoolwearprocess.Thisbehaviourhasadirectinfluenceonenergyconsumptionandontoollife.Inparticular,diamondtoolwearnecessitatesappropriatedefinitionsandmeasurements.Inotherwords,itisnecessarytoestablish,inaclearandunequivocalway,theparametersthatcharacterisethewearprocessandtheirmeasurementbymeansofareliableandreplicableprocedure.Theaimofthepresentstudyistodefineatestprotocolregardingwearofsintereddiamondtools.Thetotalabsenceofbibliographicreferencesornormsregardingtheproceduresforconductingweartestsonsintereddiamondtoolshasmadeitimperativetoprepareanadaptabletestprotocolthatoffersauniversallyvalidmodeforcarryingoutthemacro-geometricweartestwiththeaimofobtainingreplicableandcomparableresults.Itisanindispensableinstrumentforcorrectlycarryingouttestsandforreliablyinterpretingtheresults.Itoffersstonemachiningcompaniesthepossibilityofcomparingtoolsthatproducerssellasbeingsimilar,butduringmachiningpresentextremelydifferingperformances.Infact,atthepresentstate,diamondtoolsavailableonthemarketarecharacterisedsolelybythespecificationofthematerialtheycanprocess,whileothertechnicalfeaturesaresubjecttoindustrialpatentand,therefore,areunknowntomarbleandgranitemachiningfirms.Thisprotocolcouldbeusedbytoolmanufacturerstoevaluatetheperformanceoftheirtoolscomparedtothoseofcompetitorsandatthesametimetoequiptheirsup-plieswithinformationontheusefullifeofthetoolsoffered.Thislastaspectrepresentsaservicethattransformersarerequestingwithincreasinginsistence.Theguidelinesformingthisprotocolhavebeentakenfromexistingnormsforsingle-cuttools[6].Theprotocoldevelopedsofarregardsteststobecarriedoutinthelab,giventheprecisionandthustheslownessofthetestsinvolved.Theprotocolhasallowedthedevelopmentofknowledgeofthewearprocessofdiamonds,whichconstitutetoolsformachiningnaturalstones,whichinturnconstitutesthebasisformachiningoptimisation.Thefollowingparagraphsdescribethepropertiesofdiamondtoolsusedincuttingnaturalstonesandtheirrelationshipwithwear.Thetestprotocolanditsapplicationtotwotypesoftoolsaredescribedinthefollowingsections.

2Wearofsintereddiamondtoolsformachiningnaturalstone

Diamondtoolsusedfornaturalstonemachiningcanbeclassifiedincuttingtools,suchaswires,blades,disksandmills,andtoolsformachiningsurfaces,suchasgrindersandmillsofdifferentshapesandprofiles.Inbothcasesthetoolconsistsofasupport,asuper-abrasivegritandabound.Thesupportisthepartofthetooluponwhichtheabrasivegritisfixed.Itgivesthetooltheappropriateform,transmitskineticenergyfromthemachinerollerstotheabrasivegritandabsorbsthestrengthscreatedduringthemachiningprocess.Thesuper-abrasivegrithasthetaskofremovingthematerial.Itspropertiesaregranulometry,shapeandboundmatrixconcentration.Thegranulometryexpressesthemeasurementofthesuper-abrasivegritsize.The

formofthegritmayberegularorirregularaccordingtothequalityoftheactualgrain.Concentrationisthequantity,inweight,ofthediamondgritforsectorunitvolume.Theboundisthatalloywhichblocksthesuper-abrasivetothetoolsupportsothatitcancarryoutthecutting,milling,sharpening,smoothingandprofilingeconomicallyandinatechnicallycorrectmanner.Theboundmustguaranteetwocontrastingrequisites:

cuttingcapacityandlongtoollife.Finally,theboundmusthavewearresistancesuitedtothetypeoftoolsuper-abrasive,suchasallowingthecorrectprotrusioninrelationtotheprocesstobecarriedoutandthefeaturesofthematerialbeingmachined,butaboveallitmustallowthelossofworngrittoencouragereplacementbynewgritexistingwithinthematrix.Themetalsmakinguptheboundmixtureareiron,copper,tungsten,cobaltandnickel.Thediamondtoolwearistheresultofthewearprogressionofbothdiamondgritandtoolbinding.Itischaracterisedbyasequenceofsteps[7,8].Firstly,thereisaprogressiveincreaseofgritprotrusionwithrespecttobindingsurface,duetobindingerosion,thatmakesthegritcomeintocontactwiththeworkpiece.Anemergentcrystalappearsonthetoolsurface:

itscuttingabilityisscarcebecauseofitssmallheightofprotrusion.Abindingthatistoohardwouldmaketheabrasivegritexpositionsodifficultthetoolsectorresultspolishedbeforethediamondgritsarecompletelyemergedbybinding.Theprogressiveerosionofthebindingmakesthewholecrystalappearonthesurfaceofthetoolsector.Awholecrystalisadiamondgritthathasalargeheightofprotrusionandaminimumsurfacedamage.Ithasthebestcuttingperformances.Oncetheworkpieceiscontacted,thegritisroundedoffsomuchthataplateauisgeneratedonthegrittop.Itgeneratesmechanicalfrictionandthermaleffectsthatpolishthediamondgrits.Anhighpercentageofpolishedgritsmakesthesurfaceofthetoolsectorsovitreous,tocausealessefficientcuttingability.Theintermittentcontactwiththeworkpiece,causedbythetoolrotation,leadstoacyclicloadonthediamondgrit,whichdete-rioratesthegritabilitytocontrastthecuttingforcesand,finally,thegritbreakage.Thisphenomenonisenlargedbytheheterogeneousnatureoftheworkpieceandbythemachiningvibrations.Thediamondgritsresultischaracterisedbymicrofracturesandmicrocracksthatincreasethenumberofcutedgesonthegritsurface,eveniftheyreducethepenetrationdepth.Wearprogressionleadstoacompletelyfragmentaryparticleortoawornmatrixinsuchawaythatthediamondgritisreleased.Thepull-outisthephenomenonduetothereleaseofadiamondgritfrombinding,andtotheconsequentformationofacleavage.Itmayacceleratetoolwear,whenadiamondgritisremovedfromthemetallicbindingbeforeitsusefullifeiscompleted.Inthiscasetheresultingcleavagewillbeverybiganditwillinvolveaconsiderablebindingwearbeforeanewabrasivegritemerges.Conversely,ifthegritisremovedfromthemetallicbindingafteritsusefullifeisconsumed,thecleavagewillbelessdeepandlessvolumeofbindingwillbeconsumedinordertoremoveanewgrit.Thepull-outisduetoanincreaseeitherofthecuttingeffortsorofthecohesionpowertokeepfixeddiamonds.Newgritswillemergeonthetoolcuttingsurfaceandthewearcyclewillbeginagain.

Theprogressionofdiamondtoolwearconsumesthediamondandthebindingconstitutingthetool.Thisimpliesthedecreaseofboththeweightandthediameterofthewholetoolandthechangeofthecylindricalshapeofthediamondtool.Thetoolmovesawayfromitsoriginalcylindricalboundarysurface.Wehaveevaluatedtheconsumptionofadiamondmillbymeansoffourvariablesthatdependonthewholetool:

thedecreaseofthetoolweight,thedecreaseofthetooldiameter,thevariationinthecylindricityofthetoolshapeandthegrindingratio.Cylindricityisaconditionofasurfaceofrevolutionwhereallthepointsofthesurfac