Life Span
When the rated life span (L) is obtained, the life span can be calculated by equation (2) if the stroke length andreciprocations of the system per minute are defined.
6 L
h = L 10 2
( 2 )
S 1 60 whereL
h : life span(h)
s : stroke length(mm)n
1 : reciprocations per minute(min
-1 )
2) Ball Screw and Support Bearing
Rated Life Span
The rated life span (L) refers to the total number of revolutions that 90% of a group of the same ball screws(support industrial bearings) can achieve without flaking when individually operated under the exact conditions.The rated life of the ball screws or support bearings is calculated by equation (3).
C 3 L = a × f F 10 6 (3) W? a whereL: rated life span(rev.)C
a : basic dynamic rated load(N)F
a : axial load(N)f
w : load factor(see Table 7) Life Span
When the rated life span (L) is obtained, the life span can be calculated by equation (4) if the stroke length andreciprocations of the system per minute are defined.
L L
h = 2
(4)
S n
1 60
whereL
h :life span(h)
s :stroke length(mm)n
1 :reciprocationsper minute(min
-1 ) :ball screw lead(mm)
f
C C : contact factor
Table 6 Contact Factor (f )
If two nut blocks are used and closely linked together in theSKR-B or SKR-D type, multiply the basic rated load by thecontact factor shown in Table 6.
Types of Nut BlocksA/C Type
B/D TypeContact Factor f C 1.00.81 f
w : load factor
Table 7 Load Factor (f W ) Table 7 shows the load factor.
Vibration or ImpactVelocity (V)f W MinuteSmallMediumLargeFor crawling:V 0.25 m/sFor slow speed:0.25 < V 1.0 m/s For intermediate speed :1.0 < V 2.0 m/sFor high speed:V > 2.0 m/s1.0 to 1.22.0 to 3.51.5 to 2.01.2 to 1.5 K: moment equivalent coefficient (LM guide)
If a moment load is incurred, the load-carrying distribution on the LM guide increases locally. In this case, multiply themoment value with the moment equivalent coefficient shown in Table 8 to make the load calculation.K
× 10
A , K
B , and K
C show the moment equivalent coefficients in the M
A , M
B , and M
C directions respectively.
Table 8 Moment Equivalent Coefficient (K)
Model
K
A K
B K
C SKR33 - ASKR33 - BSKR33 - C
SKR33 - DSKR46 - ASKR46 - BSKR46 - C
SKR46 - D
1.42
-1 1.42 × 10
-1 5.05 × 10
-2 2.47 × 10
-2 2.47 × 10
-2 5.05 × 10
-2 2.39 × 10
-1 2.39 × 10
-1 5.05 × 10
-2 3.54 × 10
-2 3.54 × 10
-2 5.05 × 10
-2 9.51 × 10
-2 9.51 × 10
-2 3.46 × 10
-2 1.70 × 10
-2 1.70 × 10
-2 3.46 × 10
-2 1.46 × 10
-1 1.46 × 10
-1 3.46 × 10
-2 2.36 × 10
-2 2.36 × 10
-2 3.46 × 10
-2 K
A : moment equivalent coefficient in the M
A direction K
B : moment equivalent coefficient in the M
B directionK
C : moment equivalent coefficient in the M
C directionNote: For the SKR-B and SKR-D types, the moment equivalent coefficient shows the value applied when two nut blocks are closely linked together.
8