Rexroth: Screw Assemblies. Catalog (R999001185/2020-03) - page 18
Planetary Screw Assemblies PLSA |
259
Lubrication
Lubrication
cc
Do not use greases containing solid particles (e.g. graphite or MoS2)!
cc
If other lubricants are used, this may lead to a reduction in the relubrication intervals, the achievable travel in short-stroke
applications, and the load capacities. Possible chemical interactions between the plastic materials, lubricants and preservative
oils must also be taken into account.
cc
If your application makes greater environmental demands (i.e. cleanroom, vacuum, foodstuff application, strong or aggres-
sive metalworking fluids, or extreme temperatures) please contact us, since a special test, and possibly a special lubricant, will be
required. Please have all information about your application to hand.
cc
When using in other sectors, e.g.: food industry, clean room, vacuum etc. or at extreme temperatures, or if the lubrication is
exposed to process media, the standard initial lubrication and anti-corrosion agents used prior to shipment may not be suitable,
or they may be incompatible with the relubrication lubricant. In this case, please consult us in advance!
cc
Even under normal operating conditions, the system must be relubricated at the latest after 2 years due to aging of the
grease. Please note the reduced load ratings according to the technical notes.
Recommendation:
In general, you should not apply the grease all in one go; rather, apply several smaller amounts.
Grease lubrication
Planetary Screw Assemblies are designed to be lubricated with NLGI Class 2 grease. The advantage of grease lubrication is that the Plane-
tary Screw Assembly can run long distances on one supply of grease.
Lubricating grease
We recommend using Dynalub 510 with the following properties:
--
NLGI grade 2 lithium-based high-performance grease as per DIN 51818
(KP2K-20 according to DIN 51825)
--
Good water resistance
-–
Corrosion protection
Under conventional environmental conditions, this ground-fiber, homogeneous grease is
ideally suited for the lubrication of linear elements:
--
For loads of up to 50% C
-–
For short-stroke applications ≥ 1 mm
--
For the permissible speed range for Planetary Screw Assemblies
The product and material safety data sheets are available on our website at
Material numbers for Dynalub 510:
--
R3416 037 00 (cartridge 400 g)
-–
R3416 035 00 (hobbock 25 kg)
For more information on Dynalub 510, see Page 259.
260
Screw Assemblies | Planetary Screw Assemblies PLSA
Lubrication
Initial lubrication of the PLSA
Fully assembled PLSAs are prelubricated with Dynalub 510 before shipment. In versions
(Basic lubrication)
without prelubrication, the initial lubrication quantities according to Table 1 must be applied
to the nut unit via the lube hole prior to commissioning. Please follow the described proce-
dure.
In versions with a gap-type seal, the stroke-dependent lubrication quantity according to
Table 1 must additionally be applied when commissioning is carried out.
Relubrication of the Planetary
Stroke > nut length L:
Screw Assemblies
If the relubrication interval according to Diagram 1 or Diagram 2 has been reached,
relubricate the amount stated in Table 1.
Stroke < nut length L:
Carry out a lubricating stroke on a regular basis (if possible)! Reducing the relubrication
interval according to Table 1 by a factor of at least 3 means that the relubrication quantity
can be reduced by the same factor. Please follow the described procedure.
Lubricant quantity (cm3)
d0 x P
Gap-type seal/cover plate wiper
Lip seal
Initial lubrication
Relubrication
Initial lubrication
Relubrication
20 x 5
10 + Ls / 115
5 + Ls / 115
10
5,0
25 x 5/10
10 + Ls / 90
5 + Ls / 90
10
5,0
30 x 5/10
20 + Ls / 75
10 + Ls / 75
20
10,0
39 x 5/10
35 + Ls / 60
17,5 + Ls / 60
35
17,5
48 x 5/10
50 + Ls / 50
25 + Ls / 50
50
25,0
60 x 10/20
150 + Ls / 40
75 + Ls / 40
150
75,0
75 x 10/20
250 + Ls / 30
125 + Ls / 30
250
125,0
Table 1
Ls = stroke length (mm)
The nut is prelubricated; the stroke-dependent quantity of grease must be applied before
the assembly is commissioned.
Apply the stated quantity of grease through the nut unit in several partial amounts. The nut
unit must be moved through the full stroke during this process.
Conditions:
--
Temperature ≤ 60 °C
-–
Relubrication interval applies as long as the lubricant is not spun off by the screw or
removed.
Load-dependent
Relubrication interval for
Relubrication interval for
relubrication intervals
gap-type seal/wiper
lip-type seal
10,0
10
s
= relubrication interval
(106 revs.)
Fm
= average load
(N)
1,0
C = dynamic load capacity
(N)
d0 = nominal diameter
(mm)
1
0,1
0
0,1
0,2
0,3
0,4
0,5
0
0,1
0,2
0,3
0,4
0,5
d0 <
60 mm
Fm/C
Fm/C
d0 ≥
60 mm
Diagramm 1
Diagramm 2
Planetary Screw Assemblies PLSA |
261
Lubrication
Oil lubrication
Oil lubricant
We recommend using Shell Tonna S 220, which has the following properties:
--
Special demulsifying oil CLP or CGLP as per DIN 51517-3 for machine bed tracks and
tool guides
--
A blend of highly refined mineral oils and additives
-–
Can be used even when mixed with significant quantities of metalworking fluids
We recommend using piston distributors from SKF. These should be installed as close as
possible to the lube ports of the nut units. Long lines and small line diameters should be
avoided, and the lines should be laid on an upward slant.
Initial lubrication of the PLSA
(Basic lubrication)
Fully assembled PLSAs are prelubricated with Dynalub 510 before shipment. In versions
without prelubrication, the initial lubrication quantities according to Table 3 must be applied
to the nut unit via the lube hole.
Please follow the described procedure. When using single-line distributor systems, care
should be taken that all lines and the piston distributors (including the connection to the nut
unit) are filled before performing basic lubrication or relubrication.
Position specification
Lube hole: The connection should be at the top wherever possible (horizontal mounting orientation).
Relubrication of the Panetary Screw Assemblies
Apply the relubrication quantity according to Table 3 to the lube port when the specified
relubrication interval has been reached.
The pulse count can be calculated as the quotient (rounded to the next whole figure) of the
relubrication quantity and the piston distributor size.
The lubricant cycle time can then be obtained by dividing the relubrication interval by the
calculated pulse count.
d0 x P
Lubricant quantity (cm3)
Gap-type seal/cover plate wiper/ lip seal
Initial lubrication
Relubrication
20 x 5
2,7
1,4
25 x 5/10
3,0
1,5
30 x 5/10
3,5
1,8
39 x 5/10
12,0
6,0
48 x 5/10
20,0
10,0
60 x 10/20
50,0
25,0
75 x 10/20
80,0
40,0
Table 2
Load-dependent
Apply the oil quantity via the nut unit. The nut unit must be traversed during this process.
relubrication intervals
Conditions:
--
Temperature ≤ 60 °C
-–
Relubrication interval applies as long as the lubricant is not spun off by the screw or
removed.
--
For gap-type seals / Wiper, horizontal mounting only.
Oil relubrication interval
s
= relubrication interval
(106 revs.)
100.000
Fm = average load
(N)
C = dynamic load capacity
(N)
d0 = nominal diameter
(mm)
d0
<
60 mm
10.000
0
0,1
0,2
0,3
0,4
0,5
d0 ≥
60 mm
Fm/C
Diagramm 3
262
Screw Assemblies | Planetary Screw Assemblies PLSA
Calculation
Calculation
On request, we can perform all calcula-
See section “Design Calculation Service Form” on page 272
tions to your specifications.
Average speed and average load Where the operating conditions vary (fluctuating speed and load), the service life must be
calculated using the average values Fm and nm.
--
Where the speed fluctuates, the average
|n1| · qt1 + |n2| · qt2 + ... + |nn| · qtn
speed nm is calculated as follows:
nm =
1
100%
The following applies to the effective equiv-
F
>
2.8 · Fpr
Feff n
= |Fn|
alent bearing load:
3
2
|Fn|
d0 x P
Fpr (N)
F
≤
2.8 · Fpr
Feff n
=
+ 1
· Fpr
2.8 · Fpr
20 x 5
1,180
25 x 5
1,580
25 x 10
1,010
30 x 5
1,840
30 x 10
1,470
39 x 5
2,290
39 x 10
1,960
48 x 5
2,700
48 x 10
2,410
60 x 10
2,910
60 x 20
2,320
75 x 10
3,800
75 x 20
3,000
--
where the load fluctuates and the speed
is constant, the average load Fm is cal-
3
3
3
3
qt1
qtn
Fm =
Feff 1
·
+ Feff 2
· + .qt2 Feff n
·
2
culated as follows:
100%
100%
100%
-–
Where both the load and the speed fluc-
tuate, the average load Fm is calculated
3
3
3
3
|n1|
qt1
|n2|
qt2
|nn|
qtn
Fm =
Feff 1
·
·
+
Feff 2
·
·
+ ... +
Feff n
·
·
3
as follows:
nm
100%
nm
100%
nm
100%
Feff 1, Feff 2, ... Feff n
= effective equivalent axial load during phases 1 ... n
(N)
Feff n
= effective equivalent axial load during phase n
(N)
Fm
= equivalent dynamic axial load
(N)
Fn
= axial load during phase n
(N)
Fpr
= internal axial load on the nut unit due to the preload
(N)
n1, n2, ... nn
= speeds in phases 1 ... n
(rpm)
nm
= average speed
(rpm)
qt1, qt2, ... qtn
= discrete time step in phases 1 ... n
(%)
Planetary Screw Assemblies PLSA |
263
Calculation
Nominal service life
3
C
3
L
C
L =
·
106
4
C = Fm ·
5
Fm =
6
Service life in revolutions L
F
m
106
3
L
106
Service life in hours Lh
L
Lh =
7
nm · 60
DCmachine
Lh machine = Lh ·
8
DC
PLSA
Drive torque and drive power
Drive torque Mta
FL · P
for conversion of rotary motion into linear
Mta =
9
2,000 · π · η
motion:
Mta ≤ Mp
Transmitted torque Mte
FL · P · η’
Mte =
10
for conversion of linear motion into rotary
2,000 · π
motion:
Mte ≤ Mp
The dynamic drag torque must be taken into account for preloaded nut units.
Drive power Pa
Mta · n
Pa =
11
9,550
C
= dynamic load rating
(N)
DCmachine
= duty cycle of the machine
(%)
DCPLSA
= duty cycle of the PLSA
(%)
FL
= thrust force
(N)
Fm
= equivalent dynamic axial load
(N)
L
= nominal service life in revolutions
(-)
Lh
= nominal service life of the PLSA
(h)
Lh machine
= nominal service life of the machine
(h)
Mp
= maximum permissible drive torque
(Nm)
Mte
= transmitted torque
(Nm)
Mta
= drive torque
(Nm)
n
= speed
(rpm)
nm
= average speed
(rpm)
P
= lead
(mm)
Pa
= drive power
(kW)
η
= mech. efficiency (η ≈ 0.8)
(-)
η´
= mech. efficiency (η´ ≈ 0.7)
(-)
264
Screw Assemblies | Planetary Screw Assemblies PLSA
Calculation
cc
With critical applications, you must
C0
= Static load rating
(N)
pay attention to the information below.
S0 = C0 / (F0 max
)
12
F0 max = Maximum static load
(N)
S0
= Static load safety factor
(-)
Static load safety factor S0
You must verify mathematically any struc-
Design of the static load safety factor in relation to the operating conditions
tural design involving rolling contact with
regard to the static load safety factor.
Operating conditions
Static load safety factor S0
Overhead arrangements and applications representing a high
≥ 12
In this connection, F0 max represents the
hazard potential
maximum load amplitude that can occur,
High dynamic load when at standstill, contamination.
8 - 12
which can affect the screw drive.
Normal design of machinery and plant without full knowledge of the
It does not matter whether this load is
5 - 8
load parameters or connection details.
exerted only for a short period.
Full knowledge of all the load data.
It may represent the peak amplitude of an
3 - 5
Vibration-free operation is ensured.
overall dynamic loading.
For design purposes, the data shown in the
table applies.
If there are health and safety hazards, protection against falling loads must be provided.
Calculation example Service life
Proposed PLSA: 30 x 5, tolerance grade T5
F1
=
50,000 N at n1 =
10 rpm for q1 =
6% of the duty cycle
Operating conditions
F2
=
25,000 N at n2 =
30 rpm for q2 =
22% of the duty cycle
The service life of the machine should be
F3
=
8,000 N at n3 =
100 rpm for q3 =
47% of the duty cycle
40,000 operating hours with the PLSA
F4
=
2,000 N at n4 =
1,000 rpm for q4 =
25% of the duty cycle
operating 60% of the time.
100%
Calculation procedure
6
22
47
25
nm =
·
|10| +
·
|30| +
·
|100| +
·
|1,000|
1
100
100
100
100
Average torque nm
nm = 304 rpm
Average load Fm for variable load and
3
3
|10|
6
3
|30|
22
3 |100|
47
3 |1,000|
25
variable speed
F
m =
50000 ·
·
+
25000
·
·
+
8000
·
·
+
2000
·
·
3
304
100
304
100
304
100
304
100
Fm = 8 757 N
Required service life L
L
= Lh · nm · 60
(revolutions)
The service life L can be calculated by
DCPLSA
Lh = Lh machine ·
transposing formulas
7 and
8 :
DC
machine
60
Lh = 40,000 ·
= 24,000 h
100
L
= 24,000 · 304 · 60
L = 437,760,000 revolutions
Basic dynamic load rating C
3
437 760 000
C = 8 757 ·
5
C ≈ 66 492 N
106
Result and selection
e.g. PLSA, size 30 x 5 R, with single nut
Attention:
Now a selection can be made from the
with flange FEM-E-S, and screw in
Take into account the dynamic load rating
dimension tables:
tolerance grade T5.
of the screw end bearing used!
Dyn. load rating C = 87 KN.
cc
Take into account correction factor
fac of the tolerance grade! See page 255.
Planetary Screw Assemblies PLSA |
265
Calculation
Cross-check
Now the following can be selected from the product tables:
Size 30 x 5 R
Backlash
Preload
FEM-E-S, with preload class C0
FEM-E-S, with preload class C2
Load capacity Cdyn. = 87,000 N
Load capacity Cdyn. = 87,000 N
Correction factor fac = 1.0
Correction factor fac = 1.0
Cross-check
Cross-check
Service life of the selected ball
The following applies to the effective
screw drive in revolutions
equivalent bearing load:
3
F
>
2.8 · Fpr
Feff n
= |Fn|
1,0 87 000
L
106
3
8 757
2
|Fn|
F
≤
2.8 · Fpr
Feff n
=
+ 1
· Fpr
2.8 · F
pr
L ≈ 981 · 106 revolutions
Feff n = effective equivalent axial load during phase n
(N)
Fn
= axial load during phase n
(N)
Fpr
= internal axial load on the nut unit due to the preload
(N)
Service life in hours Lh
981 • 106
L
2.8 x Fpr = 2.8 x 1.840 N = 5152 N
h
304 • 60
Lh ≈ 53,760 hours
- F1 = 50,000 N > 5,152 N !Feff1 = 50,000 N
- F2 = 25,000 N > 5,152 N !Feff2 = 25,000 N
- F3 = 8,000 N > 5,152 N !Feff3 = 8,000 N
1,5
2 000
- F4 = 2,000 N < 5,152 N !Feff4 =
+1
1 840 N = 3 010 N
5 152
3
3
|10|
6
3
|30|
22
3 |100|
47
3 |1000|
25
Fm =
50000 ·
·
+
25000
·
·
+
8000
·
·
+
3010
·
·
304
100
304
100
304
100
304
100
Fm = 8 826 N
3
1,0 87 000
L
106
8 826
= 957 · 106 revolutions
6
957
10
L
h
= 52,467 hours
304
60
The service life of both PLSAs (with standard backlash/with standard preload) exceeds the required service life
of 40,000 x 60% = 24,000 hours. The selection of a smaller PLSA is consequently possible,
subject to a review of it being undertaken.
266
Screw Assemblies | Planetary Screw Assemblies PLSA
Calculation
Critical speed ncr
must be made for guidance by a nut with
The characteristic speed and the max.
The critical speed ncr depends on the
backlash. The operating speed should not
permissible linear speed must be taken into
diameter of the screw, the type of end
reach more than 80% of the critical speed.
account, see “Technical Notes”.
fixity, and the free length lcr. No allowance
Example
According to the graph, the critical speed
The maximum operating speed in our
is 3,900 rpm.
calculation example of
Screw diameter
=
30 mm
The permissible operating speed is
n4 = 1,000 rpm is therefore below the
Length lc
=
1,200 mm
3,900 rpm x 0.8 = 3,120 rpm.
permissible operating speed.
End fixity II (fixed bearing - floating bearing)
10000
10000
10000
10000
1000
1000
1000
d2
7
13
ncr fncr
2
10
(rpm)
lcr
ncrp =
0.8 · ncr (rpm)
1000
14
100
100
1000
10000
End fixity:
Length lcr (mm)
A = fixed bearing
ncr
= Critical speed
(rpm)
B = floating bearing
ncrp = Permissible operating speed
(rpm)
C = without bearing
lcr
fncr
= Coefficient determined by bearing
ls
d2
= Root diameter of screw ( see dimension tables)
(mm)
lcr
= Critical length for preloaded nut systems
(mm)
ls
= Bearing - bearing distance
(mm)
For non-preloaded nut systems lcr = ls
For screw ends Form 312, 612, 622, the end fixity can be assumed
to be “fixed”
End fixity
I
II
III
IV
fncr - value
27.4
18.9
12.1
4.3
Planetary Screw Assemblies PLSA |
267
Calculation
Permissible axial load on screw
The permissible axial load on the screw Fc
A safety factor of s ≥ 2 must be taken into
Fc (buckling load)
depends on the diameter of the screw, the type of
consideration when determining the permis-
end fixity, and the effective unsupported length lc.
sible axial load.
Example
Screw diameter
=
30 mm,
According to the graph, the theoretically permis-
This therefore lies above the maximum operat-
Length lc
=
1,200 mm
sible axial load is 115 kN.
ing load of F1 = 50 kN used in our calculation
End fixity IV (fixed bearing - floating bearing)
Applying the safety factor 2 yields a permissible
example.
axial load on the screw in operation of
For more information on buckling, see next page.
115 kN : 2 = 57.5 kN.
d24
4
10000
15
F
10
(N)
c fFc
lc2
16
Fcp
(N)
Fc2
Fc
= Theoretically permissible axial
load on screw
Fcp
= Permissible axial load on screw
during operation (N)
fFc
= Corrector value determined by
bearing
1000
d2
= Root diameter of screw, see
dimension tables (mm)
lc
= unsupported thread length
End fixity:
coefficient fFc
nut fixed
nut floating
A - A
F
F
lc
100
A - B
F
F
End fixity I
End fixity IV
lc
40.6
20.4
A - C
F
F
lc
B - B
F
F
End fixity II
End fixity V
lc
20
25
30
39
48
60
75
20.4
10.2
10
A - C
F
F
End fixity III
lc
2.6
A - C
F
F
End fixity VI
lc
2.6
End fixity:
fFc value
End fixity
A = fixed bearing
2.6
III / VI
100
1000
Length lc (mm)
10000
B = floating bearing
C = without bearing
1000
10000
10.2
V
1000
10000
20.4
II / IV
1000
10000
40.6
I
268
Screw Assemblies | Planetary Screw Assemblies PLSA
End Bearings
Notes on buckling
The effective buckling length lc of the screw is the maximum unsupported screw length in the direction of the force’s flow between the nut
unit and the fixed bearing (center-to-center distance) or between the nut unit and the screw end.
For buckling load calculations, the nut is taken into consideration as a bearing.
For “nut fixed,” the following conditions must be met:
--
zero-backlash nut,
-–
rigid attachment of the nut to the linear guide,
-–
the nut unit is not subjected to moment loads, i.e. a linear guide absorbs any arising moments,
-–
no distortive stresses due to external factors (for example, temperature).
If one or more of the conditions for “nut fixed” are not met, the appropriate coefficients for “nut floating” must be used instead.
Case III occurs in applications with driven nuts, for example, when the nut is stationary and the screw rotates. The nut can then be
regarded as a fixed bearing.
CaseVI arises only when the nut unit is not supported by any linear guide.
End Bearings
Design notes, installation
Housing
C
Bearing design
For customer-machined screw ends, please
consider the design notes given for screw
IT4
ends and housings.
For Rexroth screw end designs, see “End
IT5
C
Machining Details.”
Rexroth delivers complete drive systems,
1,6
including the end bearings. Calculations
are performed with the formulas used in the
antifriction bearing industry.
1,6
Planetary Screw Assemblies PLSA |
269
End Bearings
Mounting
Angular-contact thrust ball bearings and
deep-groove ball bearings
When mounting the angular-contact thrust
be subjected only to tension amounting to a
Outer raceway markings
ball bearings LGF and LGN, ensure that
maximum of 70% of their yielding point.
for paired bearings
the mounting forces are exerted only on
The screw-down (LGF) bearings have a
the bearing rings. Never apply mounting
groove on the cylindrical surface of the
forces via the anti-friction bearing elements
outer raceway for disassembly. The individ-
or the seal rings! The two sections of the
ual bearings of the bearing pair series
inner raceway may not be separated during
LGF-C... and LGN-C... are marked on the
assembly or disassembly for any reason!
cylindrical surfaces of the outer raceways
Tighten the mounting screws for screw-
(see Figure). The markings reveal the
down or flange-mounted bearings in cross-
bearing sequence. The sealing rings should
wise sequence. The mounting screws may
face outwards after proper mounting.
Slotted nut
The bearings are preloaded by tightening
The two set screws are then alternately
raceways of the bearings are dimensioned
the nuts.
tightened using a hexagon socket wrench.
in such a way as to achieve a defined
In order to prevent settling phenomena, we
The components are disassembled in the
bearing preload sufficient for most applica-
recommend first tightening the slotted nut
reverse order, i.e. the set screws have to be
tions when the slotted nut is tightened
by twice the value of the tightening torque
removed before the slotted nut.
(MA in accordance with Dimension Table).
MA and then easing the load. Only then
The slotted nuts can be used several times
should the slotted nut be retightened to the
when properly assembled and disassem-
specified tightening torque MA.
bled by competent personnel. The inner
Lubrication of the end bearings
Bearings for Panetary Screw Assemblies are lubricated with grease for a lifetime of reliable service. It should be noted, however, that grease
lubrication does not facilitate the dissipation of heat in the bearings. The bearing temperature should therefore not exceed 50 °C, particularly
in machine tool applications. At higher temperatures circulating oil lubrication must be set up. Angular-contact thrust ball bearings of series
LGF, LGN are lifetime-lubricated with KE2P-35 grease as per DIN 51825. For regreasing, the quantities stated in the table below can be
applied via the lube ports provided on the bearings. Where there are pairs of bearings, please note that each bearing must be individually
lubricated via the lube port. Each bearing must be lubricated with half the value shown in the table.The maximum interval can be assumed to
be 350 million revolutions, in which case the larger of the two quantities should be used. As a rule, the initial grease quantity will therefore
last for the entire service life of a Planetary Screw Assembly.
Relubrication quantities for angular-contact thrust ball bearings
Abbreviation
Quantity (cm3)
Abbreviation
Quantity (cm3)
1)
2)
1)
LGN-B-1545
LGF-B-1560
0.49
0.38
LGN-C-2052
LGF-C-2068
1.74
1.09
LGN-C-3062
LGF-C-3080
2.17
1.30
LGN-C-3572
LGF-C-3590
3.48
1.96
1) Shortened lubricating interval max. 10 M revolutions
2) Where there are pairs of bearings, lubricate each bearing via the lube port.
Lubricate each bearing with half the value shown in the table.
270
Screw Assemblies | Planetary Screw Assemblies PLSA
End Bearings
Resulting and equivalent bearing
loads
For angular-contact thrust ball bearings
Fax
= resulting axial
LGN and LGF6
bearing load
(N)
Fcomb = X · Frad + Y · Fax
20
Angular-contact thrust ball bearings are
Fcomb = combined equivalent load
(N)
preloaded. The chart shows the result-
Frad
= radial bearing load
(N)
ing axial bearing load Fax as a function of
preload and axial operating load FLax.
For a purely axial load Fcomb = Fax.
Internal preload limit and resulting bearing load
α = 60°
X
Y
18000
Fax
1.90
0.55
17000
≤ 2.17
Frad
d=50
16000
Fax
0.92
1.00
> 2.17
15000
Frad
14000
d=40
13000
α
= pressure angle
d=301)
12000
Fax
= resulting bearing load
11000
1)
d=25
FLax
= operating load
10000
X, Y
= dimensionless factor
9000
8000
7000
If the radial operating forces are not insig-
6000
d = 35
nificant, the equivalent bearing loads are
d = 30
calculated according to formula 20.
5000
Bearings for Panetary Screw Assemblies are
4000
d = 20
also able to accommodate tilting moments.
3000
d = 17
Limit values
d = 12
The moments that usually occur due to the
2000
weight and drive motion of the screw do not
1000
d = 10
d = 6
generally need to be incorporated into the
2000
4000
6000
8000
10000
12000
14000
16000
18000
calculation of the equivalent bearing load.
Operating load FLax (N)
1) Four row version
cc
Separate technical dimensioning to determine the limit values is absolutely necessary for all attachments (e.g. pillow block
units, bearing assembly, etc.)
Planetary Screw Assemblies PLSA |
271
End Bearings
Permissible static axial load for
C0
F0ax p ≤
bearing series LGF
2
The permissible static axial load of LGF
series bearings in screw-down direction is:
The static axial load rating C0 is stated in the Dimension Tables.
Average speed and average bearing load
3
n1
qt1
n2
qt2
qtn
When the bearing load varies in steps over
nn
22
Fm
Fcomb13
Fcomb23
Fcombn3
n
100
100
nm
100
m
nm
a specific period of time 22, calculate the
dynamic equivalent bearing.
When the speed varies, use formula 23. In
qt1
qt2
qtn
n
n1
+
n2
nn
23
these formulas qt
denotes the discrete time
m
100
100
100
steps for the individual phases in %.
Service life and load safety factor
3
C
L
·
106
24
Fcomb
Nominal service life
3
16 666
C
The nominal service life is calculated
L
·
25
h
nm
Fcomb
as follows:
Attention:
take the dynamic load rating of the nut
into account!
Static load safety factor
C0
The static load safety factor for machine
S
0 =
26
tools should not be lower than 4.
F0max
C
= dynamic bearing load rating
(N)
F0ax p
= permissible static axial bearing load
(N)
Fcomb
= combined equivalent load
(N)
Fcomb1 ... Fcombn = combined equivalent axial load in phases 1 ... n
(N)
Fm
= dynamic equivalent bearing load
(N)
L
= nominal service life in revolutions
(-)
Lh
= nominal service life in operating hours
(h)
n1 ... nn
= speeds in phases 1 ... n
(rpm)
nm
= average speed
(rpm)
qt1 ... qtn
= discrete time steps in phases 1 ... n
(%)
272
Screw Assemblies | Planetary Screw Assemblies PLSA
Design Calculation Service Form
Bosch Rexroth
Company:
Linear Motion Technology
Contact:
E-mail:
97419 Schweinfurt / Germany
Telephone:
Find your local contact person here: www.boschrexroth.com/adressen
Application
New design
Revised design
Operating conditions
Discrete time step parameters
or
Dynamic cycle parameters
Discrete time steps
Speed
Action of force x
Section
T1
T2
T3
T4
T5
T6
T7
T8
T9
T10
T11
T12
(%)
(1/min)
T1 =
n1 =
Path
(mm)
T2 =
n2 =
V
(m/s)
T3 =
n3 =
a
(m/s2)
T4 =
n4 =
Time
(s)
T5 =
n5 =
Action of force x
T6 =
n6 =
F1
F2
F3
F4
F5
F6
Forces
(N) =
Mass
(kg) =
Max. stroke
(mm) =
Bearing type
Installation Position
Horizontal
1.
Tight
Tight
Vertikal
Ls
Drawing enclosed
2.
Tight
Loose
(recommended)
Ls
Delivery with bearing
3.
Tight
Free
Ls
Required life:
Operating temperature:
°C Up to
°C
Type of lubrication:
Short description of the application / unusual operating conditions:
Visit out official homepage and use the provided configurators and our dimensioning program Linear Motion Designer free of charge.