毕业设计怎么翻译Word格式文档下载.docx
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毕业设计怎么翻译Word格式文档下载.docx
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石峰毕业设计(论文)英文翻译
fundamentalsnumbercalcontrolofmachinetools
machinetools
machinetoolsaremachinesforcuttingmetals.themostimportantofmetalusedinindustryarelathes,drillingmachinesandmillingmachines.otherkindsofmetalworkingmachinesarenotsowidelyusedinmachiningmetalsasthesethree.
drillingisperfurmedwitharotatingtoolcalledadrill.mostdrillinginmetaldonewithatwistdrill.themachineusedfordrillingiscalledadrillpress.operationssuchasreamingandtapping,arealsoclassifiedasdrilling.reamingconsistsofremovingasmallamountofmetalfromaholealreadydrilled.
tappingistheprocessofcuttingathreadinsideaholesothatacapscreworboltmaybethreadedintoit.
thelatheiscommonlycalledthefatheroftheentiremachinetoolfamily.forturningoperations,thelatheusedasingle-point-cuttingtool,whichremovemetalasittravelspasttherevolvingworkpiece.turningoperationsarerequiredtomakemanydifferentcylindricalshapes,suchasaxes,gearblanks,pulleys,andthreadedshafts.boringoperationsareperformedtoenlarge,finish,andaccuratelylocateholes.milingremovesmetalwitharevolving,multiplecuttingedgetoolscalledmilingcutter.milingcutteraremadeinmanystylesandsizes.somehaveasfewastwocuttingedgesandothershave30ormore.milingcanproduceflatorangledsurfaces,grooves,slots,gearteeth,andotherprofile,dependingontheshapeofthecuttersbeingused.
shapingandplanningproduceflatsurfaceswithasingle-point-cuttingtool.inshaping,thecuttingtoolonashaperreciprocatesormovesbackandforthwhiletheworkisfedautomaticallytowardsthetool.inplanning,theworkpieceisattachedtoaworktablethatreciprocatespastthecuttingtool.thecuttingtoolisautomaticallyfedintotheworkpieceasmallamountoneachstroke.
grindingmakesuseofabrasiveparticlestodothecutting.grindingoperationsmaybeclassifiedasprecisionornon-precision,dependingonthepurpose.precision
grindingisconcernedwithgrindingtoclosetolerancesandverysmoothfinish.non-precisiongrindinginvolvestheremovalofmetalwhereaccuracyisnotimportant.
fundamentalsnumbercontrol
controllingamachinetoolbymeansofapreparedprogramisknownasnumericalcontrol,ornc.ncequipmenthasbeendefinedtheelectronicindustriesassociation(eia)as“asysteminwhichactionsarecontrolledbythedirectinsertionofnumericaldataatsomepoint.thesystemmustautomaticallyinterpretatleastsomeportionofthisdata.”
inatypicalncsystemthenumericaldatawhichisrequiredforproducingapartismaintainedonapunchedtapeandiscalledthepartprogram.thepartprogramisarrangedintheformofblockofinformation,whereeachblockcontainsthenumericaldatarequiredtoproduceonesegmentoftheworkpiece.thepunchedtapeismovedforwardbyoneblockeachtimethecuttingofasegmentiscompleted.thepunchedcontains,incodedform,alltheinformationneededforprocessingasegmentoftheworkpiece:
thesegmentlength,itscuttingspeed,feed,etc..dimensionalinformation(lenth,width,andradiiofcircles)andthecontourform(linear,circular,orother)aretakenformanengineeringdrawing.dimensionsaregivenseparatelyforeachaxisofmotion(x,y,etc.).cuttingspeed,feedrate,andauxiliaryfunction(coolantonandoff,spindledirection,clamp,gearchange,etc.)areprogrammedaccordingtosurfacefinishandtoleracerequirements.
preparingthepartprogramforancmachinetoolrequiresapartprogrammer.thepartprogrammermustpossessknowledgeandexperiencesinmechanicalengineering.partprogrammersmustbefamiliarwiththefunctionofncmachinetoolsandmachiningprocessandhavetodecideontheoptimalsequenceofoperations.
inncmachinetoolseachaxisofmotionisequippedwithaseparatedrivingdevicewhichreplacesthehandwheeloftheconventionalmachine.thedrivingdevicemaybeadirectcurrent(dc)motor,ahydraulicactuator,orasteppingmotor.thetypeselectedisdeterminedmainlybythepowerrequirementofthemachine.
thencmachinetoolsystemcontainsthemachinecontrolunit(mcu)andthemachinetoolitself.themcuhastoreadanddecodethepartprogram,toprovidethedecodedinstructionstothecontrolloopsofthemachineaxesofmotion,andtocontrolthemachinetooloperation.
themcuconsistsoftwomainunits:
thedataprocessingunit(dpu)andthecontrolloopsunti(clu).thefunctionofthedpuistodecodetheinformationreceivedformthetape,processitandprovidedatatothedlu.suchdatacontainsthenewrequiredpositionofeachaxis,itsdirectionofmotionandvelocity,andauxiliarycontrolsignalstorelays.ontheotherhand,thecluprovidesasignalannouncingthatthepreviousiscompletedandthatthedpucanreadanewblockofthepartprogram.thecluoperatesthedrivesattachedofthemachinelead-screwsandreceivesfeedbacksignalsontheactualpositionandvelocityofeachoneoftheaxes.eachlead-screwisequippedwithaseparatedrivingdeviceanfaseparatefeedbackdevice,butthelatterexistsonlyinaclosed-loopsystem.
incncsystem,thedpufunctionsareperformedbythecontrolprogramcontainedinthecnccomputer.themajorpartoftheclu,however,isalwaysimplementedinthemostsophisticatedcncsystem.
numbericalcontrolofmachiningprocess
numbericalcontrolofmachinetoolsbycomputershasgreatadvanceinrecentyears.generally,automaticmachinetoolsareefficientandaccuratewhenlargequantitiesofpartsofthesameshapearerequired,butchangingfromoneautomaticcycletoanotherisalongandexpensiveprocessandwouldonlybecarriedoutforalongrun.buttherearemanyexampleswhenonlyafewpartsarerequiredanditisinsuchworkthatthecomputer-controlledmachineisvaluable.
therearetwotypesofcomputers-digitalandanalogue.adigitalcomputerworkswithnumbersgivenindigitalform,adigitbeingoneofacertainsetofsymbolsusedtoshownumbers.itisthedigitalcomputerwhichisusedinelectronicdataprocessing.theanaloguecomputerisbasedonananalogyofquantity.itdealswithphysicalquantitiesandnotnumbers.
inadigitalcontrolsysteminformationformadrawingisputonadiscwhichis
putintoacomputerwhichcomputersfromtheinformationtothecontinuousmotionofthecuttingtool.theoutputisputonadiscwhichisputintothemachinetoolcontroluntilwhenrequired.onecomputerservicesanumberofmachines.disccanbestoredandusedanynumberoftimesinfuturecases,simplybyreplayingthemifthesamepartsarewantedagain.forbestresult,theelectronicequipmentandthemachinetoolmustbedesignedtogether.
thismethodhasalsobeenappliedtothecontrolofoxygencuttingofsteelplates.whenirregularshapesarerequired,asinshipbuilding,ithasbeenthepracticetomakeamodelandtofollowitsoutlinebyhandcontrol,amethodwhichdoesnotalwaysgiveaccuateresults.again,inf
ormationisprocessedbyaspecialcomputerwhichthenpreparesadiscforuseinthecontrolconsoleofthecuttingmachine.withthisdiscthemachinecanautomaticallycutplatesofcomplicatedshapesveryaccurately.thisdevelopmenthasparticularimportanceformakingsteelplatesandisagoodexampleofautomationappliedtobatchproduction.
programmingfornc
aprogramfornumericalconsistsofasequenceofdirectionsthatcausedancmachinetocarryoutacertainoperation,machiningbeingthemostcommonlyusedprocess.programmingforncmaybedonebyaninternalprogrammingdepartment,ontheshopfloor,orpurchasedfromanoutsidesource.also,programmingmaybedonemanuallyorwithcomputerassistance.
theprogramcontainsinstructionsandcommands.geometicinstructionspertaintorelativemovementbetweenthetoolandtheworkpiece.processinginstructionspertaintospindlespeeds,feed,tools,andsoon.travelinstructionspertaintothetypeofinterpolationandsloworrapidmovementsofthetoolorworktable.switchingcommandspertaintoon/offpositionforcoolantsupplies,spindlerotation,directionofspindlerotation,toolchange,workpiecefeeding,clamping,andsoon.
(1)manualprogramming.manualpartprogrammingconsistsoffirstcalculatingdimensionalrelationshipsofthetool,workpiece,andworktable,basedontheengineeringdrawingsofthepart,andmanufacturingoperationstobeperformedandtheirsequence.aprogramsheetisthenprepared,whichconsistsofthenecessary
informationtocarryouttheoperation,suchascuttingtools,spindlespeeds,feeds,depthofcut,cuttingfluids,power,andtoolorworkpiecerelativepositionsandmovements.basedonthisinformation,thepartprogramisprepared.usuallyapapertapeisfirstpreparedfortryingoutanddebuggingtheprogram.dependingonhowoftenitistobeused,thetapemaybemadeofmoredurablemylar.
someonekonledgeableabouttheparticarprocessandabletounderstand,read,andchangepartprogramscandomanualprogramming.becausetheyarefamiliarwithmachinetoolandprocesscapabilities,skilledmachinistscandomanualprogrammingwithsometraininginprogramming,however,theworkistedious,andtimeconsuming,anduneconomicalandisusedmostlyinsimplepointto-pointapplications.
(2)computer-aidedprogramming.computer-aidedpartprogramminginvolvesspecialsymbolicprogramminglanguagesthatdeterminethecoordinatepointsofcorners,edges,andsurfacesofthepart.becausenumericalcontrolinvolvestheinsertionofdataconcerningworkpiecematerialsandprocessingparameters,programmingmustbedonebyoperatorsorprogrammerswhoareknow
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