84
Bosch Rexroth AG
| Tightening Technology
3 608 878 300
System 350
| 3 608 878 300/2019-03
Calculation of total power loss
4.2.7
Reduce cycle time
The possible cycle time of a tightening spindle (effective minimum time for a tightening process) is
determined by two factors:
•
The length of all tightening steps and synchronization times of the tightening channels to each other
•
The heat dissipation of the tightening spindles and servo amplifiers
4.2.7.1
Total duration for all tightening steps
The total duration of all tightening steps can be determined by the expected maximum angle of turn and
the selected speed of each tightening step. Thanks to the high acceleration when starting and stopping
the spindles, these times need not be taken into account.
The total duration of all tightening steps or minimum cycle time is calculated by the sum of the individual
times:
t
cycle
= t
tight
+ t
pre
+ t
end
(for a three-stage tightening process)
4.2.7.2
Heat dissipation from tightening spindle and servo amplifier
Heat dissipation is influenced by the difference in temperature in the module (motor/servo amplifier) and
the ambient temperature.
The amount of heat that has to be dissipated depends on the speed and torque of the motor and also the
cycle time (spindle run time in percent per cycle). The following diagrams show the connections regarding
the maximum permissible ambient temperature of 55
°
C and a fully equipped card rack field with 5
tightening channels. The actual tightening time is assumed to be 4 seconds.
Fig. 4–12:
Maximum performance of a tightening channel (left) and maximum possible tightening torque depending on cycle time
and tightening case hardness (right) for size 2 spindles with i > 1 on the output drive
P
V
P
G
T
n
P
1
t
1
n
P
2
t
2
n
P
3
t
3
+
+
+
T
---------------------------------------------------------------------------------------------------------------------
=
–
Max. heat dissipation capacity of the servo amplifier installed in the
BT356
- - -
Max. heat dissipation capacity of the motor
–
Hard tightening case
–
Soft tightening case
2GE19
2GE26
2GE19
2GE26
200
400
600
800
1000
0
5
10
15
T [ Nm]
n [1/min]
1
0
10
T [ Nm]
8
6
4
2
2
3
4
5
6
EC302/2GE26
s
t [s]
20
25
Summary of Contents for Rexroth Tightening System 350
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