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1、Lesson17AdvantagesofCNCTextNumericalcontrolhasbeenusedinindustryforover40years.Simplyput,numericalcontrolisamethodofautomaticallyoperatingamanufacturingmachinebasedonacodeofletters,numbers,andspecialcharacters.WhenNumericalControlisperformedundercomputersupervision,itiscalledComputer
2、NumericalControl(CNC).ComputeristhecontrolunitsofCNCmachines.Today,computernumericalcontrol(CNC)machinesarefoundalmosteverywhere,fromsmalljobshopstoFortune500companies.CNCversusManualMachinesComputernumericalcontrolisacompletedeparturefromtheconventionalmachinetooloperationwhereanope
3、ratorormachiniststudiesanengineeringdrawingorpointandguidesacuttingspindlebasedontheprintinformation.Thesuccessfuloperationofaconventionalmachinetooldependsinlargepartontheskilloftheoperatorormachinistdevelopedovermanyyearsofpractice.WithCNC,thedrawingsarestudiedandtheinformationabou
4、ttheworkpieceorpartisconvertedtoaseriesofappropriatecodenumbersbythepartprogrammer.Thecodenumbersrepresenteverymovement,path,oractionthemachinetoolmusttaketoproperlymachinetheworkpiecedescribedintheengineeringdrawing.Thecompleteseriesofcodesnecessarytoproduceasingleworkpieceonamachin
5、etoolisknownasapartprogram.Themovementsandfunctionsofthemachinetoolhavenowbecometheprogrammer’sresponsibility,whiletheroleoftheoperatorisdrasticallychanged.Thusthebasicfunctioningofthemachinedoesnotrestwiththepersonwhoisstandingbymonitoringtheoperation,butwiththeonewhodevelopedthepar
6、tprograminacodedformwhichguidesanddirectstheworkpiecemachining.Machinetoolscannotreadnumbers,however,thecodedinstructionsarereadbyaprogramreaderwhichispartoftheoverallMachineControlUnitoftencalledtheMCU.ThefunctionoftheMCUistoactuponthecodedinstructionstoconvertthemintomovementandope
7、rationofthemachinetool.Normallythecontrolunitoutputsignalsareconvertedbyelectronic,hydraulicormechanicalservomechanisms.ItisimportanttoknowthatCNCisnotamechanicalbrainandcannotthink,evaluate,judge,discern,orshowanyrealadaptability.Sometimesachoiceofalternativesorlimitscanbesetupinthe
8、programsotha