Siemens SINUMERIK 840C Installation Instructions Manual page 238

09.95
308*
Default value
200
The limiting frequency of the C axis actual value encoder is entered in machine data 308*.
The limiting frequency can be taken from the encoder manufacturer's specifications.
Pulses from the encoder may be lost when the limiting frequency is exceeded. Actual value
acquisition will then not be correct and C axis operation is no longer possible. Alarm 1004*
"Feedrate too high" is triggered.
Note:
MD 308* is used only if a separate encoder is provided for C axis operation.
If not, the limiting frequency of the spindle encoder (MD 462*) is monitored also in C axis
operation.
312*
Default value
0
Feedforward control is used to reduce the inaccuracy caused by the following error as much
as possible.
For feedforward control, the set part position is multiplied by the feedforward factor and fed
directly to the speed controller input. For static feedforward control, this value is fed directly to
the position controller input while for dynamic feedforward control it is fed to the position
controller input using a first order time-delay element after a delay specified in machine data
392*. No feedforward control is applied to the associated axis if feedforward factor 0 is entered
in 312*.
Option (6FC5 150-0AS03-0AA0) must be set to activate feedforward control.
The feedforward factor can be adapted to suit the rigidity of the machine and the resulting
acceleration/deceleration of the axes. By using feedforward control, the following error is
reduced by the amount of the feedforward factor.
Assuming a feedforward factor of 1000 at zero speed, the following error will be approximately
0. However, it should be taken into account that this setting produces overshoots. To avoid
this, use the setpoint smoothing factor (MD 1272*).
See Section entitled "Functional Descriptions".
Note:
As from SW 4, for 8 parameter sets
316*
Reference point pointer compensation +
320*
Default value
0
*) MD offset means 127 instead of 6127
_______
1) The feedforward control can be switched off via PLC MD with SW 2 and higher.
©
Siemens AG 1992 All Rights Reserved
SINUMERIK 840C (IA)
6 NC Machine Data (NC MD), NC Setting Data (NC SD)
Limiting frequency C axis encoder
Lower input limit
0
Feedforward control factor
Lower input limit
+0
Reference point pointer compensation -
Lower input limit
+0
6FC5197- AA50
6.4 Axis-specific MD 1 (axial data 1)
Upper input limit
16 000
Upper input limit
1 000
1)
Upper input limit
249 MD offset*)
Active on
Power On
Units
kHz
Active
–
Units
0.1 %
Active on
Power On
Active on
Power On
Units
6–53