外文翻譯--現(xiàn)代制造技術(shù)及其發(fā)展.doc

科技譯文譯文一：ThedevelopmentofNCThefirstNCmachinesusedvacuuintubes,electricalrelays,andcomplicatedmachine-controlinterfaces.Thesecondgenerationofmachinesutilizedimprovedproved.NCunderwentoneofthemostrapidchangesknowninhistory.Thethirdgenerationusedmuchimprovedintegratedcircuits.ComputerhardwarebecameforthefirsttimeReadOnlyMemory(ROM)technology.ROMwastypicallyusedforprpgramstorageinspecial-purposeapplications,leadlingtotheappearanceofthecomputernumericalcontrol(CNC)system,CNCwassuccessfullyintroducedtopracticallyeverymanufacturingprocess.Drilling,milling,andturningwereperformedon“machiningcenters”and“turningcenters.”CNCtiikoverglasscutting,patternmaking,electricaldischargemachining,steel-millrollgrinding,coofdinatemeasuring,electronbeamwelding,tubebending,drafting,printedcircuitmanufacturing,coilwinding,functionaltesting,robots,andmanyotherprocesses.Asetofpreprogrammedsubroutines,namedcannedcycles,weredevelopedforuseinroutineoperations.TheywererecordedintotheROMsandremainedthereevenafterpowerwasshutoff.Forthefirsttime,thisconceptmadeitpossibletoreadthemachinegprogramintomemoryandtooperatethemachinefrommemory.Inadditiontotheadvantagesofediting,theproblemscausedbyerroneoustapereadingdisappeared.Alongwiththemanycannedcycleoptions,CNCbuildersintroduceddisplaysforvisualeditingofpareprogramsinmemory.Variousin-cycleproblemsgeneratedalarmsandhundredsofdiagnosticmessageswhichcouldbedisplayedasapplicable.Practicallyeveryfunctionofthemachinewastiedintothesystemandmonitoredduringoperation.Aconstantsurfacespeedcontrolwasincorporatedandcontinuouslyanticipatedthemostefficientspindlespeedforthenextcuttominimizetimelostforspindleacceleration.Theconventionallinearandcircularinterpolationincartesian(rectangular)coordinatesweresupplementedbypolarcoordinatesandhelicalinterpolation.Safezones,whichcouldbesetthroughprogrammedcodesorinternalparameters,createdanelectroniccrashbarriertopreventtoolcollision.Thelattergroupoffeaturesmarkedthearrivalofhightechnologytothemanufacturingormetalcuttingindustry.Theimprovementindriveswasasimportantforthesystemasthecontributionofthemicroprocessorortheminicomputer.Thefeeddrives,usuallyknownasservodrives,consistofamotoranditscontrolwhichreceivesitsmotioninstructionsfromtheCNC.Theirperformanceisessentialtotheaccuracy,reliability,andflexibilityoftheCNCsystem.Theopen-loopsystemisnormallyusedinsimplepoint-topoint,orpositioningsystems,althoughimprovementsintechnologyhavemadeitpossibletoinstallthesystemincontouringsystemsaswell.Theclosed-loopconfigurationismoreaccurateandreliable,asreflectedbyitshighercost.AlthoughmanyCNCsystemsstillusehydraulicorpulsemotors,theDCdriveshavegaineddominanceonamuchlargerscale.Inmostcases,thedrivepackagesarepurchasedfromspecializeddrivesystembuilders.Thesedirectcurrent(DC)permanent-mangerwouldfieldservomotorsrangefrom3000revolutionsperminute(rpm)tolessthan1rpmwithoutstalling.Theydeveloppeaktorquecapabilitieswithhighsideaccelerationandlowinertiaforoptimizedsystemresponse.Mostdrivesystemsofferachoicebetweentransistorizedsilicone-controlledrectifiersandpulsewidthmodulationoverthefullrangeofamplifiedvoltages.Thesedrivescannowwidthmodulationoverthefullrangeofamplifiedvoltages.Thesedrivescannowdrivevirtuallyanyleadscrew.Theirhigh-responesinnercurrentloopsprovidereliableregulationoftorque-loaddisturbances.Theycanalsobebuiltwithhigh-gainpreamplifierstoclosehigh-band-widthvelocityloops.TheDCdrivesprovidetheanswertothemostessentialneedsofacceleration,deceleration,stopping,andconstantvelocity,withinherentshaftstiffnessforsuccessfuloperationoftheCNCsystem.Thesamedrivesystemsactuaterobots,transferlines.Flightsimulators,graphicplotters,etc.Asthesedrivesareinfinitelyvariableandfullyregenerative,theycanprovideformaximumperformanceandcontroloverthewholerangeofthemotor.Byeliminatinggearboxesandclutches,thecostofdrivesforthethird-generationCNCsystemswasreducedsubstantially.Thefourth-generationmicroprocessorCNCincorporatedinmanycasesthecontroversialbubblememory.Thebubblesaremagneticgarnetcrystalsgrownonnonmagneticsubstrate,ranginginsizefrom2to30micrometres,andusedasnonvolatiledatastorage.Althoughatthisstageitisnotcompetitiveinthelargecomputers,thebubblememoryisclosingthecostgapwithdiskstoragedevices.Insensitivetoadversetemperaturechanges,dust,andvibration,thebubblememoryhasdemonstratedsuperiorinshopenvironment.GeneralNumericsintroduceditsfourth-generationCNCusingbubblememory,howeverHitachi,anotherelectronicgiant,believesthatbubblememorywillprovidetheeconomicalanswertodirectnumericalcontrol(DNC).Amongthestrengthsofthefourth-generationmicroprocessorCNC(MCNC)areaddedpartprogrammemorystorage,reductionofprintedcircuitboards,programmableinterface,fastermemoryaccess,parametricsubroutines,andmacrocapabilities.Thesystemusercannowwritespecificcannedcyclesdirectedtoparticularapplications(“usermacros”),farmoreeconomicalandefficientthanconventionalcannedcycles.Mathematicalcalculationswithdo-loopsubroutinesusingvariablescannowbeincorporatedinthepartprogram.Themicroprocessorcontrolsbothcomputationsandmotioncommands.Thus,followinganin-processgaging,anout-of-toleranceconditionwillbefedback,andthetooloffsetwillbeautomaticallymodifiedtoachievethedesiredpartdimensions.譯文一:現(xiàn)代制造技術(shù)及其發(fā)展第一代數(shù)控裝備的是真空管、繼電器及復(fù)雜的機(jī)械控制接口；第二代數(shù)控裝置則采用了小型電子管及后來的固件電路。隨著計(jì)算機(jī)技術(shù)的不斷發(fā)展，NC裝置以歷史上最快的速度得到了發(fā)展；第三代數(shù)控裝置采用了性能好得多的集成電路。隨著計(jì)算機(jī)硬件愈來愈便宜，可靠性愈來愈好，數(shù)控裝置制造商首次引入了ROM技術(shù)。在專用設(shè)備中使用ROM來儲(chǔ)存程序，從而使CNC系統(tǒng)問世。CNC系統(tǒng)成功地應(yīng)用于幾乎每一個(gè)制造工藝，如在加工中心和車削中心上完成鉆、銑和車削加工，還應(yīng)用于玻璃切割、模型制造、電火花加工、鋼鐵廠軋混磨削、坐標(biāo)測量、電子束焊接、彎管、制圖、印刷電路板制作、繞線、功能測試、機(jī)器人及許多其他工藝。研制開發(fā)了一套預(yù)先編制好的子程序，叫做固定循環(huán)供日常操作時(shí)使用。這些程序記錄在ROM內(nèi)，失電后仍能保留。加工程序可存入存儲(chǔ)器，并從存儲(chǔ)器取出指令來操作機(jī)