Siemens SINUMERIK 840C - Manual (Page 238)

09.95 6 NC Machine Data (NC MD), NC Setting Data (NC SD)
6.4 Axis-specific MD 1 (axial data 1)
Limiting frequency C axis encoder 308*
Default value Lower input limit Upper input limit Units
200 0 16 000 kHz
Active on
Power On
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.
Feedforward control factor 312*
Default value Lower input limit Upper input limit Units
0 +0 1 000 0.1 %
Active
–
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. 1)
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
Reference point pointer compensation - 320*
Default value Lower input limit Upper input limit Units
0 +0 249 MD offset*)
Active on
Power On
Reference point pointer compensation + 316* Active on
Power On
*) 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 6FC5197- AA50 6–53
SINUMERIK 840C (IA)