机械加工钻床中英文对照外文翻译文献Word文档格式.docx
《机械加工钻床中英文对照外文翻译文献Word文档格式.docx》由会员分享,可在线阅读,更多相关《机械加工钻床中英文对照外文翻译文献Word文档格式.docx(7页珍藏版)》请在冰豆网上搜索。
DrillingandMillingMachines
Uprightdrillingmachinesordrillpressesareavailableinavarietyofsizesandtypes,andareequippedwithasufficientrangeofapindlespeedsandautomaticfeedstofitthenedsofmostindustries.Speedrangesonatypicalmachinearefrom76to2025rpm.,withdrillfeedfrom0.002to0.020in.perrevolutionofthespindle.
Radialdrillingmachinesareusedtodrillworkpiecesthataretoolargeorcumbersometoconvenientlymove.Thespindlewiththespeedandfeedchangingmechanismismountedontheradialarm;
bycombiningthemovementoftheradialarmaroundcolumnandthemovementofthespindleassemblyalongthearm,itispossibletoalignthespindleandthedrilltoanypositionwithinreachofthemachine.Forworkthatistoolargetoconvenientlysupportonthebase,thespindleassemblycanbeswungoutoverthefloorandtheworkpiecesetonthebesidethemachine.
Plainradialdrillingmachinesprovideonlyforverticalmovementofthespindle;
universalmachinesallowthespindletoswivelaboutanaxisnormaltotheradialarmandtheradialarmtorotateaboutahorizontalaxis,thuspermittingdrillingatanyangle.
Amultispindledrillingmachinehasoneormoreheadsthatdrivethespindlesthroughuniversaljointsandtelescopingsplinedshafts.Allspindlesareusuallydrivenbythesamemotorandfedsimultaneouslytodrillthedesirednumberofholes.Inmostmachineseachspindleisheldinanadjustableplatesothatitcanbemovedrelativetotheothers.Theareacoveredbyadjacentspindlesoverlapsothatthemachinecanbesettodrillholesatanylocationwithinitsrange.
Themillingoperationinvolvesmetalremovalwitharotatingcutter.Itincludesremovalofmetalfromthesurfaceofaworkspiece,enlargingholes,andformcutting,suchasthreadsandgearteeth.
Withinankneeandcolumntypeofmillingmachinethecolumnisthemainsupportingmemberfortheothercomponents,andincludesthebasecontainingthedrivemotor,thespindle,andthecutters.Thecutterismountedonanarborheldinthespindle,andsupportedonitsouterextremitybyabearingintheoverarm.Thekneeisheldonthecolumnindovetailslots,thesaddleisfastenedtothekneeindovetailslots,andthetableisattachedtothesaddle.Thus,thebuild-upthekneeandcolumnmachineprovidesthreemotionsrelativetothecutter.Afourmotionmaybeprovidedbyswivelingthetablearoundaverticalaxisprovidedonthesaddle.
Fixed-bedmillingmachinesaredesignedtoprovidemorerigiditythanthekneeandcolumntype.Thetableismounteddirectlyonthemachinebase,whichprovidestherigiditynecessaryforabsorbingheavycuttingload,andallowsonlylongitudinalmotiontothetable.Verticalmotionisobtainedbymovingtheentirecuttinghead.
Tracermillingischaracterizedbycoordinatedorsynchronizedmovementsofeitherthepathsofthecutterandtracingelements,orthepathsoftheworkpieceandmodel.Inatypicaltracermillthetracingfingerfollowtheshapeofthemasterpattern,andthecutterheadsduplicatethetracermotion.
Thefollowingaregeneraldesignconsiderationsformilling:
1.Whereverpossible,thepartshouldbedesignedsothatamaximumnumberofsurfacescanbemilledfromonesetting.
2.Designfortheuseofmultiplecutterstomillseveralsurfacessimultaneously.
3.Thelargestflatsurfacewillbemilledfirst,sothatalldimensionsarebestreferredtosuchsurface.
4.Squareinsidecornersarenotpossible,sincethecutterrotates.
GrindingMachinesandSpecialMetal-removalProcess
Randompoint-cuttingtoolsincludeabrasivesintheshapeofawheel,bondedtoabelt,astick,orsimplysuspendedinliquid.Thegrindingprocessisofextremeimportanceinproductionworkforseveralreasons.
1.Itismostcommonmethodforcuttinghardenedtoolsteelorotherheat-treatedsteel.Partsarefirstmachinedintheun-heat-treatedcondition,andthengroundtothedesireddimensionsandsurfacefinish.
2.Itcanprovidesurfacefinishto0.5µ
mwithoutextremecost.
3.Thegrindingoperationcanassureaccuratedimensionsinarelativelyshorttime,sincemachinesarebuilttoprovidemotionsinincrementsoften-thousandthsofaninch,insteadofthousandthsasiscommoninothermachines.
4.Extremelysmallandthinpartscanbefinishedbythismethod,sincelightpressureisusedandthetendencyfortheparttodeflectawayfromthecutterisminimized.
Onacylindricalgrindingmachinethegrindingwheelrotatesbetween5500and6500rpm.,whiletheworkrotatesbetween60and125rpm...Thedepthofcutiscontrolledbymovingthewheelhead,whichincludesboththewheelanditsdrivemotor.Coolantsareprovidedtoreduceheatdistortionandtoremovechipsandabrasivedust.
Materialremovalfromductilematerialscanbeaccomplishedbyusingatoolwhichisharderthantheworkpiece.HoweverduringWordWarⅡthewidespreaduseofmaterialswhichwereashardorharderthancuttingtoolscreatedademandfornewmaterial-removalmethods.Sincethenanumberofprocesseshavebeendevelopedwhich,althoughrelativelyslowandcostly,caneffectivelyremoveexcessmaterialinapreciseandrepeatablefashion.Therearetwotypesofprocesses.Thefirsttypeisbasedonelectricalphenomenaandisusedprimarilyforhardmaterials;
theseconddependsuponchemicaldissolution.
Chemicalmillingiscontrolledetchingprocessusingstrongalkalineoracidetchants.Aluminum,titanium,magnesium,andsteelaretheprincipalmetalsprocessedbythismethod.Theareatoremainuntouchedbytheetchantaremaskedwithaprotectivecoating.Forexample,theentirepartmaybedippedinthemaskingmaterialandthemaskremovedfromthoseareastobeetched,orachemicallyresistantprescribedtime,afterwhichthepartisrinsedincoldwater,themaskingremoved,thepartinspected,andthoroughlycleaned.
Therearecertaindisadvantagestoconsider.Metalwillerodeequallyinalldirections,sothatwallsoftheetchedsectionwillhavearadiusequaltothedepthofetch.Aseconddisadvantageisthatabetterfinishisobtainedonsurfacesparalleltothedirectionofrollingofasheetthanonsurfaceperpendiculartothedirectionofrolling.Thiscanbecomparedtothesurfaceobtainedwhenworkingwoodparallelto,oracrossthegrain.Athirddisadvantage,notuniquewiththisprocess,isthewarpagethatwilloccurinthin,previouslystressedsectionsetchedonjustoneside.
Chemicalmilling,however,hasmanyadvantagesoverconventionalmetal-removalmethods.Thereisnowarpageofheavysectionssuchasforgingsorextrusionswhentheetchantisappliedsimultaneouslytoallsidesforreductionofsectionthickness.Inconventionalmillingonlyonesidecanbeworkedatatime,andfrequentturningofapartisnecessarytopreventwarpage.Chemicalmillingcanbeappliedtopartsofirregularshapewhereconventionalmillingmaybeverydifficult.Light-weightconstructioncanbeobtainedwithchemicalmillingbytheeliminationofwelding,riveting,andstiffeners;
partscanbecontouredtodistributetheloadinthemostsuitablemanner.Asanexampleofthepotentialsavingsofthisprocess,ascomparedtomachinemilling,onecompanyreportsthatthecostofremovingaluminumbychem.-millingis$0.27perpoundascomparedto$1.00perpoundbyconventionalmilling.Therateofmetalremovalforchem.-millingis0.001in.foraluminum.
Electric-dischargemachiningisaprocessinwhichanelectricalpotentialisimpressedbetweentheworkpieceandthetool,andthecurrent,emanatingfromapointsourceontheworkpoiece,flowstothetoolintheformofaspark.Theforcesthataccomplishthemetalremovalarewithintheworkpieceproperand,asaresult,itisnotnecessarytoconstructtheunittowithstandtheheavypressuresandloadsprevalentwithconventionalmachiningmethods.
Thefrequencyoftheelectricaldischargerangesfrom20,00cps(cyclespersecond)forroughmachining,to50,000cpsforfinishingsuchitemsashardenedtoolsanddies.Thecurrentmayvaryfrom50amp,duringroughmachining,toaslowas0.5amp,duringfinishing.Theprocessiscurrentlyappliedtothemachiningofsingle-pointtools,formtools,millingcutters,broaches,anddiecavities.Itisalsoapplicabletotheremovalofbrokendrills,taps,andstudswithoutdamagingtheworkpieceinwhichthebrokentoolisimbedded.Otherusesarethemachiningofoilholesinahardenedpart,andthemachiningofsmallsafety-wireholesintheheadsofspecialalloybolts,suchastitanium.
Theultrasonicmachiningprocessisappliedtobothconductingandnon-conductingmaterial,andreliesentirelyuponabrasiveactionformetalremoval.Theworkpieceissubmergedinslurryoffinelyfividedabrasiveparticlesinavehiclesuchaswater.Thetooliscoupledtoanoscillatorandvibratesatfrequenciesbetween15,000and30,000cps.Thevibratingtoolcavitatestheliquid,andtheforcedrivestheabrasiveintothesurfaceoftheworkpiecetoremovemetalchipswhicharecarriedawaybytheliquid.Theaccelerationgiventheabrasivegrainsisasmuchas100,000timestheaccelerationofgravity,providingasmoothandrapidcuttingforce.
IntroductionofMachining
Machiningasashape-producingmethodisthemostuniversallyusedandthemostimportantofallmanufacturingprocesses.Machiningisashape-producingprocessinwhichapower-drivendevicecausesmaterialtoberemovedinchipform.Mostmachiningisdonewithequipmentthatsupportsboththeworkpieceandcuttingtoolalthoughinsomecasesportableequipmentisusedwithunsupportedworkpiece.
Lowsetupcostforsmallquantities.M