北美压铸压铸件公差标准(NADCA Standard, Brief)

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1、NADCAStandardLinearDimensions:StandardTolerancesLinearDimensions:PrecisionTolerancesPartingLine:StandardTolerancesPartingLineToleranceisthemaximumamountofdieseparationallowedfortheendproducttomeetspecifiedrequirementsofform,fitandfunction.ThisisnottobeconfusedwithPartingLineShiftTolerancewhic

2、histhemaximumamountdiehalvesshiftfromsidetosideinrelationtooneanother.PartingLineToleranceisafunctionofthesurfaceareaofthediefromwhichmaterialcanflowfromonediehalftotheother.ThisisalsoknownasProjectedArea.ProjectedAreaisalwaysaplustolerancesinceacompletelycloseddiehas0separation.Excessmateria

3、landpressurewillforcethedietoopenalongthepartinglineplanecreatinganoversizecondition.TheexcessmaterialwillcausetheparttobethickerthantheidealspecificationandthatiswhyProjectedAreaonlyhasplustolerance.ItisimportanttounderstandthatTableS-4A-2(ProjectedAreaTolerance)doesnotprovidePartingLineTole

4、rancebyitself.PartthicknessordepthmustbefactoredintogiveatrueideaofPartingLineTolerance.PartingLineToleranceisafunctionofpartthicknessperpendiculartotheProjectedAreaplustheProjectedAreaTolerance.Example:Analuminumdiecastinghas75in2(483.9cm2)ofProjectedAreaonthepartingdieplane.FromtableS-4A-2,

5、ProjectedAreaToleranceis+0.012.ThisiscombinedwiththetotalpartthicknesstolerancefromtableS-4A-1toobtainthePartingLineTolerance.Thetotalpartthicknessincludingbothdiehalvesis5.00in.(127mm)whichismeasuredperpendiculartothepartingdieplane(dimension“E2E1”).FromtableS-4A-1,theLinearToleranceis±0.01

6、0forthefirstinchand±0.001foreachofthefouradditionalinches.TheLinearToleranceof±0.014inchesiscombinedwiththeProjectedAreaToleranceof+0.012toyieldaStandardPartingLineToleranceof+0.026/-0.014in.orinmetricterms±0.35mmfromLinearTolerancetableS-4A-1plus+0.30mmfromProjectedAreaTolerancetableS-4A-2=+

7、0.65/-0.35mm.PartingLineShift:StandardToleranceExample:PartingLineShiftToleranceThecavityareaatthepartinglineis75inchessquared.FromTableS-4A-6,theProjectedAreaPartingLineShiftToleranceis±0.006(±0,152mm).ThisisaddedtotheLinearTolerancefromtabl