Life Span Life Span

Model KR consists of an LM guide, ball screw, and supporting bearing. The rated life span of each componentcan be calculated based on the basic dynamic load rating shown in Rated Loads (Table 2, page 7).

LM Guide Rated life span

?Cf

3

L=

()

C

?P 50f

W C L: rated life span (km)(The “rated life span” refers to the total traveling distance that 90% of a group of the same LM guidescan achieve without flaking (flakes peeling off the metal surface) when these LM guides are individuallymoved under the same conditions.)C: basic dynamic load rating(N) P
c : calculated imposed load(N)f
w : load factor(see Table 5, page 10)f
c : contact factor(see Table 4, page 10)? If moment acts on the KR when two KR-A/C or KR-B/D nut blocks are used in a double block structure,multiply the acting moment by the equivalent coefficient shown in Table 6 on page 10 to calculate the equivalent load.P
m =K?MP
m : equivalent load (per block)(N)K: moment equivalent factor (see Table 6, page 10)M: operating moment (N?mm)(If three or more nut blocks are to be used or nut blocks are to be used with the span separated, contactTHK.)? If moment M
C acts on model KR-B/D, use the following equation to obtain the equivalent load:
P C C m =K ? M 2 ? If radial load (P) and moment act simultaneously on the KR, use the following equation to obtain theequivalent load:P
E =P
m +PP
E : total equivalent radial load(N)

Life span

When the rated life span (L) is obtained, the life span can be obtained by the following equation if the strokelength and the number of forward and reverse motions are constant:L
6 L
h =L 10 2 ? R
S ? n
1 60
h : life span(h) R
s : stroke length(mm)n
-1 1 : number of forward and reverse motions per minute (min )

Ball Screw and Supporting Bearing Rated life span

Caf 3 L= ? Fa W 10 6 L: rated life span(rev.)(The “rated life span” refers to the total number of revolutions that 90% of a group of the same ball screws(supporting bearings) can achieve without flaking when these ball screws (supporting bearings) are individually operated under the same conditions.)C

()

a : basic dynamic load rating(N)F
a : axial load(N)f
w : load factor(see Table 5, page 10)When the rated life span is obtained, the life span can be obtained by the following equation if the strokelength and the number of back and forth motions are constant.

9