外文翻译--现代制造技术及其发展.doc

科技译文译文一：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.译文一:现代制造技术及其发展第一代数控装备的是真空管、继电器及复杂的机械控制接口；第二代数控装置则采用了小型电子管及后来的固件电路。随着计算机技术的不断发展，NC装置以历史上最快的速度得到了发展；第三代数控装置采用了性能好得多的集成电路。随着计算机硬件愈来愈便宜，可靠性愈来愈好，数控装置制造商首次引入了ROM技术。在专用设备中使用ROM来储存程序，从而使CNC系统问世。CNC系统成功地应用于几乎每一个制造工艺，如在加工中心和车削中心上完成钻、铣和车削加工，还应用于玻璃切割、模型制造、电火花加工、钢铁厂轧混磨削、坐标测量、电子束焊接、弯管、制图、印刷电路板制作、绕线、功能测试、机器人及许多其他工艺。研制开发了一套预先编制好的子程序，叫做固定循环供日常操作时使用。这些程序记录在ROM内，失电后仍能保留。加工程序可存入存储器，并从存储器取出指令来操作机