Siemens SINUMERIK 840D sl Function Manual page 424

Compensations (K3)
5.7 Neural quadrant error compensation
Figure 5-34
In special cases, it might be necessary to reparameterize the error measuring times:
● Setting of very extreme values for the QEC compensation time constant. Experience
● Parameterization of the error measuring times with adaptation of the decay time of the
Overcompensation with short traversing motions
Practical experience has shown that the optimum friction compensation value calculated
from the circularity test may result in overcompensation on the relevant axis if it executes
very short axial positioning movements (e.g. on infeeds in the mm range).
To improve accuracy in such cases too, it is possible to reduce the compensation amplitude
for short traversing motions.
424
Dependency of error measuring time on acceleration rate
indicates that it is not useful to set an error measuring time of less than 10ms or more
than 200ms.
compensation value
If the adaptation of the decay time of the compensation value is active (see above), the
following rule of thumb is applicable to the parameterization of the error measuring time
for acceleration range 1:
$AA_QEC_MEAS_TIME_1 = 3 * $AA_QEC_ TIME_2
Example:
Decay time ($AA_QEC_TIME_1) = 10ms
Adaptation of decay time ($AA_QEC_TIME_2) = 30ms
The above rule of thumb produces an error measuring time for acceleration range 1 of:
$AA_QEC_MEAS_TIME_1 = 3 * 30ms = 90ms
Without decay time adaptation, the calculated setting for $AA_QEC_MEAS_TIME_1
would be merely 6 * 10ms = 60ms.
Function Manual, 01/2008, 6FC5397-1BP10-3BA0
Extended Functions