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LINEAR MOTION

Precision Ballscrews

Load Factor (fw)

3 1 (F
a13 l
1 + F
a23 l
2 + · · · · + F
an3 l
n ) . . . . . (9)LFm:mean axial load(N)F Vibration and impactVelocity (V)fw Very LightLight Medium Heavy Very low:1.0 ~ 1.2V % 0.25 m/sLow:1.2 ~ 1.50.25 2.0 m/s
an :varying load(N) l n:running distance achieved under load (F
n )(mm)L:total running distance(mm)To determine the service life in the number of revolutions orhours instead of distance, obtain the distance using the equationshown below, and calculate the mean axial load. l = l 1 + l 2 + ···· l n l 1 = N
1 · t
1 (2) Service life in hours l 2 = N
2 · t
2 l n = N
n · t
n If the number of revolutions per minute is known, the servicelife in hours can be calculated by an equation (7) using the value for the nominal life (L).Lh=L = L · whereN:number of revolutions t:time l . . . . . . . . . . . . . . .(7)60 · n 2 · 60 · S · l swhereLh:service life in hours(h) n:number of revolutions per minute(min

Ballscrew Accuracy Grades

The accuracy grades of the precision rolled ballscrews arerelated to standards ISO 3408 and DIN 69051. The accuracy grades of the ground ballscrews are controlled in accordance of the Japanese standard JIS B 1191 and JIS B 1192. Travel Variation and Travel Deviation
–1 )S:number of reciprocal operations per minute(min
–1 ) l :ballscrew lead(mm) l s:stroke length(mm) Nominal travel l u VupV2 (3) Service life in running distance This can be calculated by an equation (8) using the values forthe nominal life (L) and the ballscrew lead.Ls=L ·
c l . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .(8)10
6 Travel deviation p whereLs:service life in running distance(km) l :ballscrew lead(mm)
ep (4)Applied load and service life in consideration of the preload Definitions according to ISO 3408: ep:Tolerance on specified travel. The difference between the maximum and minimum values of the permissible actual mean travel.Vup:Permissible travel variation in relation to the nominaltravel Permissible travel deviation and travel variation in relation to the nominal travel For a ballscrew used with a preload applied to the nut, the servicelife should be calculated in consideration of the preload, which is the internal load on the nut. If you have questions about the preload, please contact us, and be sure to specify the relevant model number. (5) Mean axial load l When the axial loads applied to the ballscrew fluctuate, theservice life should be calculated based on the mean axial load of the varying axial loads.The mean axial load (Fm) is the load that makes the service life ofthe ballscrew equivalent to that under varying loads exerted during operation.Where loads vary incrementally, the mean axial load can beobtained using the following equation: Fm=
u .V2 π p:Permissible travel variation in relation to one rotation2 π rad.V300p:Permissible travel deviation over 300 mm travel.c:Travel compensation. The difference between thespecified travel and nominal travel within the usefultravel (Standard: c = 0).
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