Catalogue Caged Ball LM Guide Actuator Model SKR
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Permissible Moment (LM Guide)
The SKR-type's LM guide section can carry moment loads in all directions, even though it uses only one nut block. Table 5 shows the permissible static moment values in the M M and MC directions.
Use of one long type block (type A)
Mr
Use of one short type block (type C)
MB
Use of two long type blocks closely linked together (type B) Use of two short type blocks closely linked together (type D)
Figure 7 Permissible Static Moment in Each Direction
Table 5 Permissible Static Moment
Unit: N-m
Model
Permissible Static Moment
Mb
Mc
SKR33 - A
173
173
424
SKR33 - B
990
990
848
SKR33 - C
58
58
240
SKR33 - D
390
390
480
SKR46 - A
579
579
1390
SKR46 - B
3240
3240
2780
SKR46 - C
236
236
870
SKR46 - D
1460
1460
1740
Note 1: Symbol A, B, C, or D at the end of the model
number represents the type of nut block and the
number of them in use.
A: long type block, one piece used
B: long type block, two pieces closely linked
together
C: short type block, one piece used
D: short type block, two pieces closely linked
together
Note 2: The permissible static moments for the SKR-B or SKR-D type show a value applicable when two nut blocks are used and closely linked together.
Life Span
The SKR-type LM guide actuator with Caged Ball Technology consists of the LM guide, ball screw, and support bearing. The life span of each constituting component can be calculated based on the basic dynamic rated load shown in Rated Loads (Table 4 on p. 6).
• Calculation of Life Span 1) LM Guide ■ Rated Life Span
The rated life span (L) refers to the total traveling distance that 90% of a group of the same LM guides can achieve without flaking (flakes peeling off the metal surface) when these LM guides are individually moved under the same conditions. The rated life span of the LM guide can be obtained by equation (1).
L =
x 50
"(1)
f -P
where
L : rated life span
(km)
C : basic dynamic rated load
(N)
Pc : calculated carrying load
(N)
fw : load factor
(see Table 7)
fc : contact factor
(see Table 6)
If moment is acted on the SKR-type when using the SKR-A/-C type or the SKR-B/-D type of closely linked double nut blocks, multiply the acting moment by the equivalent coefficient shown in Table 8 to calculate equivalent load. P = K • M
m
where
Pm : Equivalent load (per block) (N)
K : Moment-equivalent factor
M : Operating moment (N-mm)
(If the SKR-type is used using three or more nut blocks or with the span separated, contact THK.) Particularly, if moment acts upon the SKR-B or SKR-D, use the following equation:
D Kc • Mc
m
2
• If a radial load (P) and moment load act on the SKR-type simultaneously, use the following equation to calculate the life span: PE = Pm + P where
PE : Total equivalent radial load (N)
7
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