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1、附錄英文原文N/CMachineToolElementN/Cmachinetoolelementsconsistofdimensioningsystems,controlsystems,servomechanismsandopen-orclosed-loopsystems.Itisimportanttounderstandeachelementpriortoactualprogrammingofanumericallycontrolledport.ThetermmeasuringsysteminN/Creferst
2、othemethodamachinetoolusestomoveapartfromareferencepointtoatargetpoint.Atargetpointmaybeacertainlocatingfordrillingahole,millingaslot,orothermachineoperation.ThetwomeasuringsystemsusedonN/Cmachinesaretheabsoluteandincremental.Theabsolutemeasuringsystemusesafix
3、edreferencepoint.Itisonthispointthatallpositionalinformationisbased.Inotherwords,allthelocationstowhichapartwillbemovedmustbegivendimensionsrelatingtothatoriginalfixedreferencepoint.FigureshowsanabsolutemeasuringsystemwithXandYdimensions,eachbasedontheorigin.T
4、heincrementalmeasuringsystemhasafloatingcoordinatingsystem.Withtheincrementalsystem,thetimethepartismoved.Figure16.2showXandYvaluesusinganincrementalmeasuringsystem.Noticethatwiththissystem,eachnewlocationbasesitsvaluesinXandYfromtheprecedinglocation.Onedisadv
5、antagetothissystemisthatanyerrorsmadewillberepeatedthroughouttheentireprogram,ifnotdetectedandcorrected.TherearetwotypesofcontrolsystemscommonlyusedonN/Cequipment:point-to-pointandcontinuouspath.Apoint-to-pointcontrolledN/Cmachinetool,sometimesreferredtoasapos
6、itioningcontroltype,hasthecapabilityofmovingonlyalongastraightline.However,whentwoaxesareprogrammedsimultaneouslywithequalvaluesa45anglewillbegenerated.Point-to-pointsystemsaregenerallyfoundondrillingandsimplemillingmachinewhereholelocationandstraightmillingjo
7、bsareperformed.Point-to-pointsystemscanbeutilizedtogenetatearcsandanglesbyprogrammingthemachinetomoveinaseriesofsmallsteps.Usingthistechnique,however,theactualpathmachinedisslightlydifferentfromthecuttingpathspecified.Machinetoolsthathavethecapabilityofmovings
8、imultaneouslyintwoormoreaxesareclassifiedascontinuous-pathorcontouring.Thesemachinesareusedformachiningarcs,radii,circles,andanglesofanysizeintwoortheredimensions.Continuous-pathma
