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外文翻译--现代制造技术及其发展.doc

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外文翻译--现代制造技术及其发展.doc

科技译文译文一ThedevelopmentofNCThefirstNCmachinesusedvacuuintubes,electricalrelays,andcomplicatedmachinecontrolinterfaces.Thesecondgenerationofmachinesutilizedimprovedproved.NCunderwentoneofthemostrapidchangesknowninhistory.Thethirdgenerationusedmuchimprovedintegratedcircuits.ComputerhardwarebecameforthefirsttimeReadOnlyMemoryROMtechnology.ROMwastypicallyusedforprpgramstorageinspecialpurposeapplications,leadlingtotheappearanceofthecomputernumericalcontrolCNCsystem,CNCwassuccessfullyintroducedtopracticallyeverymanufacturingprocess.Drilling,milling,andturningwereperformedonmachiningcentersandturningcenters.CNCtiikoverglasscutting,patternmaking,electricaldischargemachining,steelmillrollgrinding,coofdinatemeasuring,electronbeamwelding,tubebending,drafting,printedcircuitmanufacturing,coilwinding,functionaltesting,robots,andmanyotherprocesses.Asetofpreprogrammedsubroutines,namedcannedcycles,weredevelopedforuseinroutineoperations.TheywererecordedintotheROMsandremainedthereevenafterpowerwasshutoff.Forthefirsttime,thisconceptmadeitpossibletoreadthemachinegprogramintomemoryandtooperatethemachinefrommemory.Inadditiontotheadvantagesofediting,theproblemscausedbyerroneoustapereadingdisappeared.Alongwiththemanycannedcycleoptions,CNCbuildersintroduceddisplaysforvisualeditingofpareprogramsinmemory.Variousincycleproblemsgeneratedalarmsandhundredsofdiagnosticmessageswhichcouldbedisplayedasapplicable.Practicallyeveryfunctionofthemachinewastiedintothesystemandmonitoredduringoperation.Aconstantsurfacespeedcontrolwasincorporatedandcontinuouslyanticipatedthemostefficientspindlespeedforthenextcuttominimizetimelostforspindleacceleration.Theconventionallinearandcircularinterpolationincartesianrectangularcoordinatesweresupplementedbypolarcoordinatesandhelicalinterpolation.Safezones,whichcouldbesetthroughprogrammedcodesorinternalparameters,createdanelectroniccrashbarriertopreventtoolcollision.Thelattergroupoffeaturesmarkedthearrivalofhightechnologytothemanufacturingormetalcuttingindustry.Theimprovementindriveswasasimportantforthesystemasthecontributionofthemicroprocessorortheminicomputer.Thefeeddrives,usuallyknownasservodrives,consistofamotoranditscontrolwhichreceivesitsmotioninstructionsfromtheCNC.Theirperformanceisessentialtotheaccuracy,reliability,andflexibilityoftheCNCsystem.Theopenloopsystemisnormallyusedinsimplepointto–point,orpositioningsystems,althoughimprovementsintechnologyhavemadeitpossibletoinstallthesystemincontouringsystemsaswell.Theclosedloopconfigurationismoreaccurateandreliable,asreflectedbyitshighercost.AlthoughmanyCNCsystemsstillusehydraulicorpulsemotors,theDCdriveshavegaineddominanceonamuchlargerscale.Inmostcases,thedrivepackagesarepurchasedfromspecializeddrivesystembuilders.ThesedirectcurrentDCpermanentmangerwouldfieldservomotorsrangefrom3000revolutionsperminuterpmtolessthan1rpmwithoutstalling.Theydeveloppeaktorquecapabilitieswithhighsideaccelerationandlowinertiaforoptimizedsystemresponse.Mostdrivesystemsofferachoicebetweentransistorizedsiliconecontrolledrectifiersandpulsewidthmodulationoverthefullrangeofamplifiedvoltages.Thesedrivescannowwidthmodulationoverthefullrangeofamplifiedvoltages.Thesedrivescannowdrivevirtuallyanyleadscrew.Theirhighresponesinnercurrentloopsprovidereliableregulationoftorqueloaddisturbances.Theycanalsobebuiltwithhighgainpreamplifierstoclosehighbandwidthvelocityloops.TheDCdrivesprovidetheanswertothemostessentialneedsofacceleration,deceleration,stopping,andconstantvelocity,withinherentshaftstiffnessforsuccessfuloperationoftheCNCsystem.Thesamedrivesystemsactuaterobots,transferlines.Flightsimulators,graphicplotters,etc.Asthesedrivesareinfinitelyvariableandfullyregenerative,theycanprovideformaximumperformanceandcontroloverthewholerangeofthemotor.Byeliminatinggearboxesandclutches,thecostofdrivesforthethirdgenerationCNCsystemswasreducedsubstantially.ThefourthgenerationmicroprocessorCNCincorporatedinmanycasesthecontroversialbubblememory.Thebubblesaremagneticgarnetcrystalsgrownonnonmagneticsubstrate,ranginginsizefrom2to30micrometres,andusedasnonvolatiledatastorage.Althoughatthisstageitisnotcompetitiveinthelargecomputers,thebubblememoryisclosingthecostgapwithdiskstoragedevices.Insensitivetoadversetemperaturechanges,dust,andvibration,thebubblememoryhasdemonstratedsuperiorinshopenvironment.GeneralNumericsintroduceditsfourthgenerationCNCusingbubblememory,howeverHitachi,anotherelectronicgiant,believesthatbubblememorywillprovidetheeconomicalanswertodirectnumericalcontrolDNC.AmongthestrengthsofthefourthgenerationmicroprocessorCNCMCNCareaddedpartprogrammemorystorage,reductionofprintedcircuitboards,programmableinterface,fastermemoryaccess,parametricsubroutines,andmacrocapabilities.Thesystemusercannowwritespecificcannedcyclesdirectedtoparticularapplicationsusermacros,farmoreeconomicalandefficientthanconventionalcannedcycles.Mathematicalcalculationswithdoloopsubroutinesusingvariablescannowbeincorporatedinthepartprogram.Themicroprocessorcontrolsbothcomputationsandmotioncommands.Thus,followinganinprocessgaging,anoutoftoleranceconditionwillbefedback,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床除具有编辑功能外,还可避免出现由读带错误所产生的一些问题。除有许多固定循环可供任选外,还可设有显示装置(CRT),可显示储存器内零件程序的编辑,对各种循环内出现的问题可发出报警,并能显示几百个诊断信息。机床的几乎每个功能与系统连在一起,操作期间可进行监控。采用了恒线速控制,能不断使主轴保持在最佳切削转速,从而使主轴加速时间减到最小。除传统的直角坐标直线和圆弧插补外,还采用了极坐标和螺旋线插补由编码或内部参数所社定的安全区域建立了电子防撞障壁可防止刀具碰撞,这些特性标志着制造和金属切削工业水平达到了高技术。传动系统的改进和采用微处理机或小型计算机一样,对系统至关重要。进给

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