ISO 5459 - 3

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1、GermanCommentonISOCD5459-3ISO/TC213N443&ISO/TC213/WG2N158Theaimofdatumtargetsistodefineasetofsmallsupportsofthereticallyexactform,orientationandlocationrelativetoeachotheronwhichtheworkpiececanrestuniqueinorientationandlocationwithoutanyfurtherconstrain

2、t.Orientationandlocationoftolerancezonesarerelatedtothesetofdatumtargets.Inordertokeeptheworkpieceinauniqueorientationandlocationthenumberandthelocationofthedatumtargetsmustbechosenaccordingtothedegreesoffreedomoftheworkpiece.Arealisationofthedatumtarge

3、tsmaybesmallsupportsinamanufacturingorinspectiondevice.Clause5oftheCDdoesnotmeetthisphilosophy.5.1requiresfiltration,5.3requiresthattheassociatedidealfeatureisofthesameinvarianceclassasthecorrespondingnon-idealfeature.Fortheuseofdatumtargets,thereshallb

4、enofiltration.Theselectionofdatumtargetsisakindoffiltrationinitself.Theassociatedfeature,e.g.2pointsinaplaneassociatedtoacylindricalfeatureassecondarydatum,seefigures3and4,andthedatumfeaturemaybeofdifferentinvarianceclasses(planeandcylinderinfigure3and4

5、).Forclause5ofISO5459-3weproposethefollowingcontent:ISO5459-3Proposal5Datumtargets5.1GeneralAdatumtargetisapointorstraightlineorlimitedsmallareaofaplaneonwhichtheworkpiecefeaturecanrest.Datumtargetscanbeusedtoestablishasingledatumoracommondatumoradatums

6、ystem.Datumtargetsystemsdefineasetofdatumtargets(smallsupports)ofthereticallyexactorientationandlocationrelativetoeachotheronwhichtheworkpiececanrestuniqueinorientationandlocationwithoutanyfurtherconstraint.Orientationandlocationoftolerancezonesarerelat

7、edtothesetofdatumtargets.Therelationshipbetweenthedatumtargetsisgivenbytheoreticallyexactdimensions.Therealfeatureiscontactingthedatumtargets.Therebydatumtargetsdefinesituationfeatures(plane,straightline,point)towhichtheorientationsorlocationsoftoleranc

8、edfeaturesarerelated,e.g.onacastingtodefinetheposition(orientationandlocation)ofthefirstmachinedsurfacesformingthedatumsystemofthefinalmachinedpart.5.2Operations5.2.1ExtractionFortheextractionmethodsee4.1.5.2.2FiltrationUsingdatu