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外文翻译--高速研磨技术的应用与展望.doc

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外文翻译--高速研磨技术的应用与展望.doc

C1外文翻译英文中文16页5909字数HighspeedgrindingapplicationsandfuturetechnologyM.J.Jackson,,C.J.Davis,M.P.Hitchhiker,B.MillsAbstractThebasicmechanismsandtheapplicationsforthetechnologyofhighspeedgrindingwithCBNgrindingwheelsarepresented.Inadditiontodevelopmentsinprocesstechnologyassociatedwithhighspeedmachining,thegrindingmachine,coolantsystem,andthegrindingtoolalsoneedtoadapttohighspeedmachining.Workpiecerelatedfactorsinurningtheresultsofmachiningarealsodiscussed.Thepaperconcludeswithapresentationofcurrentresearchandfuturedevelopmentsintheareaofhighspeedgrinding,andthedevelopmentofhighspeedCBNcamshaftgrinding.Allrightsreserved.1.IntroductionMorethan25yearsofhighspeedgrindinghaveexpandedthefieldofapplicationforgrindingfromclassicalfinishmachiningtohighperformancemachining.Highspeedgrindingoffersexcellentpotentialforgoodcomponentqualitycombinedwithhighproductivity.Onefactorbehindtheinnovativeprocesshasbeentheneedtoincreaseproductivityforconventionalfinishingprocesses.Inthecourseofprocessdevelopmentithasbecomeevidentthathighspeedgrindingincombinationwithpreliminarymachiningprocessesclosetothefinishedcontourenablestheconfigurationofnewprocesssequenceswithhighperformancecapabilities.Usingtheappropriategrindingmachinesandgrindingtools,itispossibletoexpandthescopeofgrindingtohighperformancemachiningofsoftmaterials.Initially,abasicexaminationofprocessmechanismsisdiscussedthatrelatestheconfigurationofgrindingtoolsandtherequirementsofgrindingsoftmaterials.Theeffectofaneffectiveandenvironmentallyfriendlycoolantsystemisalsoinvestigatedinadditiontotheeffectofworkpiecerelatedvariablesonthesuitabilityofusinghighspeedgrindingtechniques.2.TheoreticalbasisofhighspeedgrindingInviewoftherandomdistributionofcuttingedgesandcuttingedgeshapes,statisticalmethodsareappliedtoanalysesthecuttingmechanismingrinding.Themeanunreformedchipthickness,hcu,andthemeanchiplength,lcu,areemployedasvariablestodescribetheshapeofthechip.Theunreformedchipthicknessisdependentonthestaticdensityofcuttingedges,Cstat,andonthegeometricandkinematicsvariables1,2C21whereVwistheworkpiecespeed,VSthegrindingwheelspeed,aethedepthofcut,deqtheequivalentgrindingwheeldiameter,andα,β,γaregreaterthanzero.Onthebasisofthisrelationship,itcanbeestablishedthatanincreaseinthecuttingspeed,assumingallotherconditionsareconstant,willresultinareductionintheunreformedchipthickness.Theworkpiecematerialismachinedwithalargernumberofabrasivegraincontacts.Atthesametime,thenumberofcuttingedgesinvolvedintheprocessdecreases.Thisleadstotheadvantagespromisedbyhighspeedgrindingwhichischaracterizedbyareductioningrindingforces,grindingwheelwear,andinworkpiecesurfaceroughness.Consequently,increasingthespeedofthegrindingwheelcanleadtoanincreaseinthequalityoftheworkpiecematerial,oralternatively,anincreaseinproductivity.Theprocesstechnologydependsonthecharacteristicsandqualityrequirementsoftheworkpiecetobemachined.Asthecuttingspeedincreases,thequantityofthermalenergythatisintroducedintotheworkpiecealsoincreases.Anincreaseincuttingspeedisnotnormallyaccompaniedbyaproportionalreductioninthetangentialgrindingforce,andthusresultsinanincreaseinprocesspower.Reducingthelengthoftimetheabrasivegrainisincontactwiththeworkpiececanreducethequantityofheatintotheworkpiece.Anincreaseinthemachiningrateoftheprocessisnecessaryforthistohappen,wherethechipthicknessisincreasedtothelevelthatappliestolowercuttingspeedswithoutC3overloadingthegrindingwheel.Experimentalresults3illustratethatincreasingthecuttingspeedbyafactoroftwowhilemaintainingthesamemetalremovalrateleadstoareductioninthetangentialforcebut,unfortunately,leadstoanincreaseintheamountofworkdone.Owingtoconstantgrindingtime,thereisanincreaseintheprocessenergyperworkpieceand,subsequently,inthetotalthermalenergygenerated.Whenthematerialremovalrateisalsoincreasedtherisingtangentialforceresultsinafurtherincreaseingrindingpower.Thequantityofthermalenergyintroducedintotheworkpieceislowerthantheinitialsituationwhenthesamemachinedworkpiecevolumeappliesdespitethehighercuttingspeedandincreasedmetalremovalrate.Theseconsiderationsshowthatmachiningproductivitycanbeincreasedusinghighspeedgrindingwithouthavingtoacceptundesirablethermaleffectsongroundcomponents.Therearethreefieldsoftechnologythathavebecomeestablishedforhighspeedgrinding.Theseare1.HighspeedgrindingwithCBNgrindingwheels.2.Highspeedgrindingwithaluminumoxidegrindingwheels.3.GrindingwithaluminumoxidegrindingwheelsinconjunctionwithcontinuousdressingtechniquesCDgrinding.Materialremovalratesresultinginasuperproportionalincreaseinproductivityforcomponentmachininghavebeenachievedforeachofthesefieldsoftechnologyinindustrialapplications4,5Fig.1.Highequivalentchipthicknessofbetween0.5and10mmareacharacteristicfeatureofhighspeedgrinding.CBNhighspeedgrindingisemployedforalargeproportionoftheseapplications.AnessentialcharacteristicofthistechnologyisthattheperformanceofCBNisutilizedwhenhighcuttingspeedsareemployed.3.GrindingtoolsforhighspeedgrindingCBNgrindingtoolsforhighspeedmachiningaresubjecttospecialrequirementsregardingresistancetofractureandwear.Gooddampingcharacteristics,highrigidity,andgoodthermalconductivityarealsodesirable.Suchtoolsnormallyconsistofabodyofhighmechanicalstrengthandacomparablythincoatingofabrasiveattachedtothebodyusingahighstrengthadhesive.Thesuitabilityofcubicboronnitrideasanabrasivematerialforhighspeedmachiningofferrousmaterialsisattributedtoitsextremehardnessanditsthermalandchemicaldurability.HighcuttingspeedsareattainableaboveallwithmetalbondingsystemsFig.2.Onemethodthatusessuchbondingsystemsiselectroplating,wheregrindingwheelsareproducedwithasinglelayercoatingofabrasiveCBNgrainmaterial.Theelectrodepositednickelbonddisplaysoutstandinggrainretentionproperties.Thisprovidesahighlevelgrainprojectionandlargechipspaces.Cuttingspeedsof280ms1arepossible6.Theservicelifeendswhentheabrasivelayerwearsout.C4ThehighroughnessofthecuttingsurfacesofelectroplatedCBNgrindingwheelshasdisadvantageouseffects.Thehighroughnessisaccountabletoexposedgraintipsthatresultfromdifferentgrainshapesandgraindiameters.AlthoughelectroplatedCBNgrindingwheelsarenotconsideredtobedressableintheconventionalsense,theresultantworkpiecesurfaceroughnesscanneverthelessbeinfluencedwithinnarrowlimitsbymeansofasocalledtouchdressingprocess.Thisinvolvesremovingtheperipheralgraintipsfromtheabrasivecoatingbymeansofverysmalldressinginfeedstepsintherangeofdressingdepthsofcutbetween2and4mm,therebyreducingtheeffectiveroughnessofthegrindingwheel7.MultilayerbondingsystemsforCBNgrindingwheelsincludesinteredmetalbonds,resinbonds,andvitrifiedbonds.Multilayermetalbondspossesshighbondhardnessandwearresistance.Profilingandsharpeningthesetoolsisacomplexprocess,however,onaccountoftheirhighmechanicalstrength.Syntheticresinbondspermitabroadscopeofadaptationforbondingcharacteristics.However,thesetoolsalsorequireasharpeningprocessafterdressing.Thepotentialforpracticalapplicationofvitrifiedbondshasyettobefullyexploited.Inconjunctionwithsuitablydesignedbodies,newbonddevelopmentspermitgrindingwheelspeedsofupto200ms1.Incomparisonwithothertypesofbonds,vitrifiedbondspermiteasydressingwhileatthesametimepossesshighlevelsofresistancetowear.Incontrasttoimpermeableresinandmetalbonds,theporosityofthevitrifiedgrindingwheelcanbeadjustedoverabroadrangebyvaryingtheformulationandthemanufacturingprocess.AsthestructureofvitrifiedbondedCBNgrindingwheelsresultsinasubsequentlyincreasedchipspaceafterdressing,thesharpeningprocessissimplified,orcanbeeliminatedinnumerousapplications.Fig.3showsatypicalmicrostructureofavitrifiedCBNgrindingwheel.TheselectionoftheappropriategradeofvitrifiedCBNgrindingwheelforhighspeedgrindingismorecomplicatedthanforaluminiumoxidegrindingwheels.Here,theCBNabrasivegrainsizeisdependentonspecificmetalremovalrate,surfaceroughness

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