320 TECHNICAL INFORMATION "MMPXBCMF 3PUBUJPOBM 4QFFE Refers to the allowable rotational speed that is 80% or less of the critical speed that matches the rotational speed of a ball screw at which there is a unique oscillation possessed by the screw shaft. The ball screw rotational speed is decided by the necessary travel speed and ball screw lead. To decide the allowable rotational speed, it is necessary to consider the following two elements. 1. Critical speed for the rotating shaft 2. Limit rotational speed of the balls circulating inside the nut 0QFSBUJOH )PVST PG #BMM 4DSFXT This refers to the total revolutions, time, or distance up until chipping begins to occur due to fatigue causes by some kind of repetitive stress on the ball rolling surface or balls. The lifespan of the ball screw is calculated from the basic dynamic load rating. See Figures 5 and 6 for expired parts that have chips. When a certain group of the same ball screws are operated with a certain axial load and 90% of the screws achieve 1 million rotations (106) without flaking in its operating life, such axial load is defined as a basic dynamic load rating. 2 8IFO DIPPTJOH JU JT OFDFTTBSZ UP FOTVSF UIF UFNQFSBUVSF JNQBDU BOE SJHJEJUZ JT TVJUBCMF GPS UIF VTBHF FOWJSPONFOU BOE TFMFDUJPO DSJUFSJB 'PS EFUBJMT TFF 1 _ PG UIF DBUBMPH UFDIOJDBM QBHFT BOE DIPPTF B CBMM TDSFX UIBU JT TVJUBCMF GPS UIF QVSQPTF PG VTF 4UFQ 4UFQ "MMPXBCMF 3PUBUJPOBM 4QFFE $IFDL -JGF $IFDL 5IF SPUBUJPOBM TQFFE PG UIF CBMM TDSFX NVTU CF MFTT UIBO UIF BMMPXBCMF SPUBUJPOBM TQFFE *G JU FYDFFET UIF BMMPXFE SPUBUJPOBM TQFFE UIF UISFBE BOE UIF OVU XJMM CF BGGFDUFE JO UIF GPMMPXJOH XBZ 4DSFX 4IBGU 8IFO UIF BMMPXBCMF SPUBUJPOBM TQFFE JT FYDFFEFE SFTPOBODF XJMM CFHJO BU B VOJRVF PTDJMMBUJOH GSFRVFODZ BOE UIJT NJHIU EJTBCMF PQFSBUJPO 'JHVSF /VU *G UIF PSCJUBM TQFFE PG UIF TUFFM CBMMT JOTJEF UIF OVU CFDPNFT MBSHF JU JT QPTTJCMF UIBU UIF DJSDVMBUJPO DPNQPOFOUT XJMM CF EBNBHFE CZ UIF JNQBDU GPSDF 'JHVSF *O PSEFS UP VTF UIF FRVJQNFOU CFZPOE UIF FYQFDUFE MJGF MJGF DBMDVMBUJPOT BSF SFRVJSFE 'JHVSF 3FTPOBUJOH #BMM 4DSFX 'JHVSF #BMM 4DSFX $JSDVMBUJPO 4USVDUVSF 5VCF 4UZMF 'JHVSF 5ISFBE *OTJEF /VU 'JHVSF 'MBLJOH PO #BMM 4DSFX $PNQPOFOUT %'PS EFUBJMT TFF 1 PO UIF DBUBMPH %'PS EFUBJMT TFF 1 PO UIF DBUBMPH Screw Shaft Steel Ball Recirculation Part Nut Steel Ball Unused Flaking on steel balls 4UFFM #BMM 5ISFBET JOTJEF OVU .BHOJGJDBUJPO PG 'JHVSF Unused Flaking on Threads
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