机械加工简要介绍(英文版)dgze

Machhiniing: Ann InntrooducctioonIn ttermms oof aannuual dolllarrs sspennt, macchinningg iss thhe mmostt immporrtannt oof tthe mannufaactuurinng pproccessses. Maachiininngcaan bbe ddefiinedd ass thhe pproccesss off reemovvingg maaterriall frrom a wworkkpieece in thee foorm of chiips. Thhe ttermm meetall cuuttiingiis uusedd whhen thee maaterriall iss meetalllic. Moost macchinningg haas vveryy loow sset-up cosst ccomppareed tto fformmingg, mmolddingg, aand casstinng pproccessses. Hoowevver, maachiininng iis mmuchh moore exppenssivee foor hhighh voolummes. Maachiininng iis nneceessaary wheere tigght tolleraancees oon ddimeensiionss annd ffiniishees aare reqquirred.Thee Maachiiningg seectiion is divvideed iintoo thhe ffolllowiing cattegooriees: Drilllinng: InttrodducttionnDrilllinng iis eeasiily thee moost commmonn maachiininng pproccesss. OOne esttimaate is thaat 775% of alll meetall-cuuttiing matteriial remmoveed ccomees ffromm drrilllingg opperaatioons.Driilliing invvolvves thee crreatioon oof hholees tthatt arre rrighht ccircculaar ccyliindeers. Thhis is acccompplisshedd moost typpicaallyy byy ussingg a twiist driill, soometthinng mmostt reeadeers willl hhavee seeen befforee. TThe figguree beeloww illlusstraatess a crooss secctioon oof aa hoole beiing cutt byy a commmonn twwistt drrilll:The chiipsmmustt exxit thrrouggh tthe fluutess too thhe ooutssidee off thhe ttooll. AAs ccan be seeen iin tthe figguree, tthe cutttinng ffronnt iis eembeeddeed wwithhin thee woorkppiecce, makkingg coooliing diffficcultt. TThe cutttinng aareaa caan bbe fflooodedd, ccoollantt spprayy miist cann bee apppliied, orr cooolaant cann bee deelivvereed tthrooughh thhe ddrilll bbit shaaft. Foor aan ooverrvieew oof tthe chiip-fformmatiion proocesss, seee thhe CChipp Foormaatioon SSecttionn.Drilllinng CCharractteriistiicsThe chaaraccterristticss off drrilllingg thhat sett itt appartt frrom othher powwereed mmetaal ccutttingg opperaatioons aree: · The chiips musst eexit oout of thee hoole creeateed bby tthe cutttinng.· Chipp exxit cann caausee prrobllemss whhen chiips aree laargee annd/oor cconttinuuouss.· For deeep hholees iin llargge wworkkpieecess, ccoollantt maay nneedd too bee deelivvereed tthrooughh thhe ddrilll sshafft tto tthe cutttinng ffronnt.· Of tthe powwereed mmetaal ccutttingg proccessses, drrilllingg onn a driill preess is thee moost likkelyy too bee peerfoormeed bby ssomeeonee whho iis nnot a mmachhiniist.Drilll PPresss WWorkk ArreaA viiew of thee meetall-cuuttiing areea oof aa drrilll prresss iss shhownn beeloww. TThe worrkpiiecee iss heeld in plaace by a cclammp ssincce ccutttingg foorcees caan bbe qquitte llargge. It is danngerrouss too hoold a wworkkpieece by hannd dduriing driilliing sinnce cutttinng fforcces cann unnpreedicctabbly gett quuitee laargee annd wwrennch thee paart awaay. Woood iis oofteen uusedd unnderrneaath thee paart so thaat tthe driill bitt caan ooverrshooot witthouut ddamaaginng tthe ttablle. Thee taablee allso hass hooless foor ddrilll ooverrshooot as welll aas wweigght redducttionn. AA thhreee-jaaw cchucck iis uusedd siincee thhreee poointts ddeteermiine a ccirccle in twoo diimennsioons. Foour-jaww chhuckks aare rarrelyy seeen sinnce offfsett off thhe bbit is nott neecesssarry. Thee neext secctioon coontaainss illlusstraatioons of driill bitt chhuckks. To gett ann iddea of thee diiffeerinng cconffiguurattionns oof tthreee aand fouur-jjaw chuuckss, ppleaase seee thhe eequiivallentt laathee chhuckks.Turnningg: EEngiine LattheTurnningg iss annothher of thee baasicc maachiininng pproccessses. Innforrmattionn innthiis ssecttionn iss orrgannizeed aaccoordiing to thee suubcaateggoryy liinkss inn thhe mmenuu baar tto tthe lefft. Tuurniing prooducces sollidss off reevollutiion whiich cann bee tiighttly tolleraanceed bbecaausee off thhe sspecciallizeed nnatuure of thee opperaatioon. Turrninng iis pperfformmed on a mmachhinee caalleeda latthe in whiich thee toool is staatioonarry aand thee paart is rottateed. Thee fiigurre bbeloow iilluustrratees aan eengiine latthe. Laathees aare dessignned sollelyy foor tturnningg opperaatioons, soo thhat preecisse cconttroll off thhe ccutttingg reesullts in tigght tolleraancees. Thee woork pieece is mouunteedonn thhechhuckk, wwhicch rrotaatess reelattivee too thhe sstattionnaryy toool.TurnninggTurnningg reeferrs tto ccutttingg ass shhownn beeloww.The terrm ""faccingg" iis uusedd too deescrribee reemovval of matteriial froom tthe flaat eend of a ccyliindrricaal ppartt, aas sshowwn bbeloow. Faccingg iss offtenn ussed to improove thee fiinissh oof ssurffacees tthatt haave beeen ppartted.Milllingg: IIntrroduuctiionMilllingg iss ass fuundaamenntall ass drrilllingg ammongg poowerred mettal cutttinng pproccessses.Milllinng iis vverssatiile forr a bassic macchinningg prroceess, buut bbecaausee thhe mmilllingg seet uup hhas so manny ddegrrees oof ffreeedomm, mmilllingg iss ussuallly lesss aaccuuratte tthann tuurniing or griindiing unllesss esspecciallly riggid fixxturringg iss immpleemenntedd. For mannuall maachiininng, milllinng iis eesseentiial to fabbriccatee anny oobjeect thaat iis nnot axiiallly ssymmmetrric. Thheree iss a widde rrangge oof ddifffereentmmilllingg maachiiness, rranggingg frrom mannuall liightt-duuty Briidgeeporrtsâ⢠tto hhugee CNNC mmachhinees ffor milllinng ppartts hhunddredds oof ffeett loong. Beeloww iss illlusstraatedd thhe pproccesss att thhe ccutttingg arrea.Milllingg: CColuumn-andd-Knnee Mannuall MiillBeloow iis iilluustrrateed aa tyypiccal collumnn-annd-kknee typpe mmanuual milll. Succh mmanuual millls aree coommoon iin jjob shoops thaat sspecciallizee inn paartss thhat aree loow vvoluume andd quuickkly fabbriccateed. Succh jjob shoops aree offtenn teermeed ""moddel shoops"" beecauuse of thee prrotootyppingg naaturre oof tthe worrk.The parrts of thee maanuaal mmilllaree seeparrateed bbeloow. Thee knnee movves up andd doown thee coolummn oon gguiddewaays in thee coolummn. Thee taablee caan mmovee inn x andd y on thee knnee, annd tthe milllinng hheadd caan mmovee upp annd ddownn.Grinndinng: InttrodducttionnGrinndinng iis aa fiinisshinng pproccesss ussed to impprovve ssurfacce ffinissh, abrradee haard matteriialss, aand tigghteen tthe tolleraancee onn fllat andd cyylinndriicall suurfaacess byy reemovvingg a smaall amoountt off maaterriall. IInfoormaatioon iin tthiss seectiion is orgganiizedd acccorrdinng tto tthe subbcattegoory linnks in thee meenu barr too thhe lleftt.Inn grrinddingg, aanabbrassive mmateeriaal rrubss aggainnst thee meetall paart andd reemovves tinny ppiecces of matteriial. Thhe aabraasivve mmateeriaal iis ttypiicallly on thee suurfaace of a wwheeel oor bbeltt annd aabraadess maaterriall inn a wayy siimillar to sanndinng. On a mmicrrosccopiic sscalle, thee chhip forrmattionn inn grrinddingg iss thhe ssamee ass thhat fouund in othher macchinningg prroceessees. Thee abbrassivee acctioon oof ggrinndinng ggeneerattes exccesssivee heeat so thaat fflooodinng oof tthe cutttinng aareaa wiith fluuid is neccesssaryy.Reassonss foor GGrinndinngReassonss foor ggrinndinng aare:1. Thee maaterriall iss tooo hhardd too bee maachiinedd ecconoomiccallly. (Thhe mmateeriaal mmay havve bbeenn haardeenedd inn orrderr too prroduuce a llow-weaar ffiniish, suuch as thaat iin aa beeariing raccewaay.2. Tolleraancees rrequuireed ppreccludde mmachhiniing. Grrinddingg caan pprodducee fllatnnesss toolerrancces of lesss tthann ±±0.000255 mmm (±0.00001 iin) on a 1127 x 1127 mm (5 x 55 inn) ssteeel ssurffacee iff thhe ssurffacee iss addequuateely suppporrtedd.3. Maachiininng rremoovess exxcesssivve mmateeriaal.Chipp Foormaatioon: InttrodducttionnBecaausee off thhe iimpoortaancee off maachiininng ffor anyy inndusstriial ecoonommy, Macchinningg Thheorry hhas beeen eexteensiivelly sstuddiedd. Thee chhip forrmattionn prroceess is thee saame forr moost macchinningg prroceessees, andd itt haas bbeenn reeseaarchhed in ordder to dettermminee clloseed-fformm sooluttionns ffor speeedss, ffeedds, andd ottherr paarammeteers whiich havve iin tthe passt bbeenn deeterrminned by thee "ffeell"off thhe mmachhiniist. Wiith CNCC maachiine toools prooduccingg paartss att evver-fassterr raatess, iit hhas beccomee immporrtannt tto pprovvidee auutommatiic aalgooritthmss foor ddeteermiininng sspeeeds andd feeedss. TThe infformmatiion preesenntedd inn thhis secctioon aare somme oof tthe morre iimpoortaant asppectts oofchhip forrmattionn. RReassonss foor mmachhiniing beiing diffficcultt too annalyyze andd chharaacteerizze ccan be summmarrizeed aas ffolllowss:· The strrainn raate is exttremmelyy hiigh commparred to thaat oof ootheer ffabrricaatioon pproccessses.· The proocesss vvariies connsidderaablyy deepenndinng oon tthe parrt mmateeriaal, temmperratuure, cuuttiing fluuidss, eetc.· The proocesss vvariies connsidderaablyy deepenndinng oon tthe toool mmateeriaal, temmperratuure, chhattter andd viibraatioon, etcc.· The proocesss iis oonlyy coonsttraiinedd byy thhe ttooll cuutteer. Unllikee ottherr prroceessees ssuchh ass mooldiing andd coold forrminng wwhicch aare conntaiinedd, aa loot oof vvariiatiion cann occcurr evven witth tthe samme cconffiguurattionn.For alll tyypess off maachiininng, inccluddingg grrinddingg, hhoniing, laappiing, pllaniing, tuurniing, orr miilliing, thhe pphennomeenonn off chhip forrmattionn iss siimillar at thee poointt whheree thhe ttooll meeetss thhe wworkk.Beeloww arre iilluustrrateed ccateegorriess off chhip typpes.