Siemens sinumerik 840D sl Function Manual page 185

Detailed description
2.2 SINUMERIK 810D and 840D
Default values for cycle times
The default settings ensure that a maximum configuration of the system can power up
reliably. The cycle times, e.g., for the NCU 573, can generally be set to lower values.
The default cycle times are as follows:
cycle 810D
CCU
Basic system clock 2.5 ms
cycle
Position control 2.5 ms
cycle
Interpolator cycle 10 ms
* with 2 channels and 12 axes
with > 2 channels
#
General example for cycle settings
The machine data assignments for cycle times are as follows:
If MD ... = ...
SYSCLOCK_CYCLE_TIME = 0.002
POSCTRL_SYSCLOCK_TIME_RATIO = 1
IPO_SYSCLOCK_TIME_RATIO = 3
2.2 SINUMERIK 810D and 840D
Interpolator cycle
The interpolator cycle defines the cycle time in which the setpoint interface to the position
controllers is updated. The interpolator cycle is important for two reasons in normal
processing:
• The product of velocities and interpolator cycles defines the geometry resolution of the
• The interpolator cycle determines the possible resolution of the velocity profiles. It must
Position control cycle
The position-control cycle is the time which it takes for the control to calculate the actual
value and transfer a new speed setpoint to the speed controller.
8
840D 840D
NCU 571 NCU 572
6 ms 4 ms
6 ms 4 ms
18 ms 12 ms
interpolated contour. A long interpolator cycle causes a large path error along curved
contours. This error is, however, reduced in the ratio interpolator / position-control cycle
by cubic fine interpolation MD 33000 $MA_FIPO_TYPE.
be adapted to the dynamics of the drives so that the machine axes traverse and
accelerate evenly (i.e., position-control cycle time </= interpolator cycle << acceleration
time constant).
840D Setting via MD
NCU 573
4*/8 ms SYSCLOCK_CYCLE_TIME
#
4*/8 ms POSCTRL_SYSCLOCK_TIME_RATIO
#
12 /40 ms IPO_SYSCLOCK_TIME_RATIO
* #
then ... = ...
System clock cycle = 2 ms
Position-control cycle = 2 ms (1 2 ms)
Interpolator cycle = 6 ms (3 2 ms)
Function Manual, 11/2006, 6FC5397-2BP10-2BA0
Special functions: Cycle Times (G3)