>> P.71
VibrationduetoforcedrotationandMinebeaMitsumi'sapproachRollingballbearingshavemultipleballsandtheirretainerasrollingelements;theyalsocontainthegreasewhichlubricatestheseparts.Becausetheballmovementinvolvesspinandslip,runoutappearinginconstantly(NRRO,non-repeatablerunout)istheoreticallyunavoidable;however,MinebeaMitsumihasusedtheknow-howaccumulatedsinceitsfoundingtodevelopbearingswhichminimizethisalmostentirely.Thatis,themutualerrorofballsphericityandballdimensionshasbeenreducedalmosttozero,enablingtheinnerandouterringgrooveroundnessandcurvaturetobemaintainedaccordingtotheidealdesign.Inthe1980s,thedemandforharddiskdrives(HDDs)begantoincreaseasVTRsandpersonalcomputerscameintowidespreaduse.InVTRs,therotationprecisionofthebearingsusedinthemotorsignificantlyaffectstheimagequality:bearingsaresocentraltoHDDsthattherotationprecisionofthespindlemotorwhichrotatesthediskdeterminesperformancesuchasmemorycapacityandprocessingspeed.Thesebearingsarecalledonforhigher-precisionroundness,sphericity,andcylindricityaswellasreducedNRRO,withmoreadvanceddemandsyearlyforprecisioninMinebeaMitsumibearings.HDDspindlemotorsswitchedinthe2000sfrombearingstofluiddynamicbearings,butthetechnologiesdevelopedthereinhavebeenappliedtotheincreasinglyminiaturizedandhigher-speedservercoolingfanmotors,vacuumcleanermotors,dentalhandpieces,etc.,withastonishingrotationspeedsoftensofthousandrotationsaminuteembeddedintheproductsthatsupportourlifestyle.Inthedevelopmentofproductsusingbearings,thecontrolofvibrationfrequencyduetoproductinherentvibrationisamajorconcernforitsinfluenceonrequisiteperformance.MinebeaMitsumihasvariousproposalsavailablebasedonitsdecadesofaccumulatedtechnologyandexperience.ConsultMinebeaMitsumiforanyproblemswithvibration.71
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