>> P.226
LoadfactorLoadappliedtoalinearmotionrollingguidecanbelargerthantheoreticalloadduetomachinevibrationorshock.Generally,theappliedloadisobtainedbymultiplyingitbytheloadfactorindicatedinTable3.Table3LoadfactorOperatingconditionsSmoothoperationfreefromshockNormaloperationOperationwithshockloadfw1～1.21.2～1.51.5～3StaticsafetyfactorGenerally,basicstaticloadratingandstaticmomentrating(orstatictorquerating)isconsideredasloadattheallowablelimitfornormalrollingmotion.However,staticsafetyfactormustbeconsideredaccordingtooperatingconditionsandrequiredperformanceofthelinearmotionrollingguide.StaticsafetyfactorcanbeobtainedbythefollowingequationandtypicalvaluesareindicatedinTable4.Equation(4)isarepresentativeequationformomentloadortorque.Staticmomentratingandmaximummomentloadineachdirectionisappliedforthecalculation.fS=C0―P0fS=T0―M0(3)(4)where,fS:StaticsafetyfactorC0:Basicstaticloadrating,NP0:Staticequivalentload,N(Orappliedload(maximumload))T0:Staticmomentrating,N・m(Orstatictorquerating)M0:Momentloadortorqueineachdirection,N・m(Maximummomentloadormaximumtorque)HighoperatingperformanceNormaloperatingconditions3～52～44～6223～52.5～3～31～531.51.52.5～3BalldiameterDiameterandlengthofroller10mm10mm×10mmPreloadload:0.05×C0equivalentBall(withoutpreload)Ball(withpreload)Roller(withoutpreload)Roller(withpreload)100020003000LoadN201510500ElasticdeformationmiFgure4PreloadandelasticdeformationbehaviorⅢ-6SeriesOperationwithvibrationand/orCrossedRollerWayLinearSlideUnitLinearBallSplineLinearBushingStrokeRotaryBushingRollerWay&FlatRollerCagePreloadshock～64～53～752.52.54～6ObjectivesofpreloadInsomecases,thelinearmotionrollingguideisusedwithclearancegiventothelinearmotionrollingguidewhenlightmotionwithsmallloadisrequired.However,forsomeapplicationsitmaybeusedwithplayintheguidingmechanismremovedorwithpreloadtoincreaserigidity.Preloadisappliedtothecontactpartsofaracewayandrollingelementswithinternalstressgeneratedinadvance.Whenaexternalloadisappliedonthepreloadedlinearmotionrollingguide,shockabsorbingwiththisinternalstressmakeselasticdeformationsmaller,anditsrigidityisincreased.(SeeFig.4)PreloadsettingPreloadamountisdeterminedbyconsideringthecharacteristicsofthemachinesorequipmentsonwhichthelinearmotionrollingguideismountedandthenatureofloadactingonthelinearmotionrollingguide.Thestandardamountofpreloadforlinearmotionrollingguidesis,ingeneral,approx.1/3ofloadwhentherollingelementsareballs(steelballs)andapprox.1/2ofloadwhentheyarerollers(cylindricalrollers).Ifthelinearmotionrollingguidesarerequiredtohaveveryhighrigiditytowithstandvibrationorfluctuatingload,alargerpreloadmaybeapplied.PrecautionforpreloadselectionEvenwhenhighrigiditymustberequired,excessivepreloadshouldbeavoided,becauseitwillproduceanexcessivestressbetweenrollingelementsandraceways,andeventuallyresultinshortlifeoflinearmotionrollingguides.Itimportanttoapplyaproperamountofpreload,consideringtheoperationalconditions.Whenusingwithalargepreload,contactIKO.LinearBushingandStrokeRotaryBushingshouldneverbegivenalargeamountofpreload.isTable4StaticsafetyfactorOperationalconditionandstaticsafetyfactor
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