数控机床的组成部分.doc

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1、N/CMachineToolElementsN/Cmachinetoolelementsconsistofdimensioningsystems,controlsystems,servomechanismsandopen-orclose-loopsystems.Itisimportanttounderstandeachelementpriortoactualprogrammingofanumericallycontrolledpart.TheteammeasuringsysteminN/Creferstothemethodamachinetoo

2、lusestomoveapartfromareferencepointtoatargetpoint.Atargetpointmaybeacertainlocationfordrillingaslot,orothermachiningoperation.ThetwomeasuringsystemsusedonN/Cmachinesaretheabsoluteandincremental.Theabsolute(alsocalledcoordinate)measuringsystemusesafixedreferencepoint(origin).

3、Itisonthispointthatallpositionalinformationisbased.Inotherwords,allthelocationstowhichapartwillbemovedmustbegivendimensionsrelatingtothatoriginalfixedreferencepoint.Theincrementalmeasuringsystem(alsocalleddelta)hasafloatingcoordinatingsystem.Withtheinferencepointeachtimethep

4、artismoved.Noticethatwiththissystem,eachnewlocationbasesitsvaluesinXandYfromtheprecedinglocation.Onedisadvantagetothissystemisthatanyerrorsmadewillberepeatedthroughouttheentireprogram,ifnotdetectedandcorrected.TherearetwotypesofcontrolsystemscommonlyusedonN/Cequipment:point-

5、to-pointandcontinuouspath.Apoint-to-pointcontrolledN/Cmachinetool,sometimesreferredtoasapositioningcontroltype,hasthecapabilityofmovingonlyalongastraightline.However,whentwoaxesareprogrammedsimultaneouslywithequalvaluesa45°anglewillbegenerated.Point-to-pointsystemsaregeneral

6、lyfoundondrillingandsimplemillingmachinewhereholelocationandstraightmillingjobsareperformed.Point-to-pointsystemscanbeutilizedtogeneratearcsandanglesbyprogrammingthemachinetomoveinaseriesofsmallsteps.Usingthistechnique,however,theactualpathmachinedisslightlydifferentfromthec

7、uttingpathspecified.Machinetoolsthathavethecapabilityofmovingsimultaneouslyintwoormoreaxesareclassifiedascontinuous-pathorcontouring.Thesemachinesareusedformachiningarcs,radii,circles,andanglesofanysizeintwoorthreedimensions.Continuous-pathmachinesaremoreexpensivethanpoint-t

8、o-pointsystemsandgenerallyrequireacomputertoaidprogrammingwhenmachiningcomp