机械专业英语文章中英文对照.docx

机械专业英语文章中英文对照

第一篇：机械专业英语文章中英文对照英语原文NUMERICALCONTROLNumericalcontrol(N/C)isaformofprogrammableautomationinwhichtheprocessingequipmentiscontrolledbymeansofnumbers,letters,andothersymbols,Thenumbers,letters,andsymbolsarecodedinanappropriateformattodefineaprogramofinstructionsforaparticularworkpartorjob.Whenthejobchanges,theprogramofinstructionsischanged.ThecapabilitytochangetheprogramiswhatmakesN/Csuitableforlow-andmedium-volumeproduction.Itismucheasiertowriteprogramsthantomakemajoralterationsoftheprocessingequipment.Therearetwobasictypesofnumericallycontrolledmachinetools：point—to—pointandcontinuous—path(alsocalledcontouring).Point—to—pointmachinesuseunsynchronizedmotors,withtheresultthatthepositionofthemachiningheadCanbeassuredonlyuponcompletionofamovement,orwhileonlyonemotorisrunning.Machinesofthistypeareprincipallyusedforstraight—linecutsorfordrillingorboring.TheN/Csystemconsistsofthefollowingcomponents：datainput,thetapereaderwiththecontrolunit,feedbackdevices,andthemetal—cuttingmachinetoolorothertypeofN/Cequipment.Datainput,alsocalled“man—to—controllink”,maybeprovidedtothemachinetoolmanually,orentirelybyautomaticmeans.Manualmethodswhenusedasthesolesourceofinputdataarerestrictedtoarelativelysmallnumberofinputs.Examplesofmanuallyoperateddevicesarekeyboarddials,pushbuttons,switches,orthumbwheelselectors.Thesearelocatedonaconsolenearthemachine.Dialsaleanalogdevicesusuallyconnectedtoasyn-chro-typeresolverorpotentiometer.Inmostcases,pushbuttons,switches,andothersimilartypesofselectorsaredigitalinputdevices.Manualinputrequiresthattheoperatorsetthecontrolsforeachoperation.Itisaslowandtediousprocessandisseldomjustifiedexceptinelementarymachiningapplicationsorinspecialcases.Inpracticallyallcases,informationisautomaticallysuppliedtothecontrolunitandthemachinetoolbycards,punchedtapes,orbymagnetictape.Eight—channelpunchedpapertapeisthemostcommonlyusedformofdatainputforconventionalN/Csystems.Thecodedinstructionsonthetapeconsistofsectionsofpunchedholescalledblocks.Eachblockrepr