Siemens SINUMERIK 840D sl Function Manual page 420

Compensations (K3)
Friction compensation (quadrant error compensation)
Time constant too high
When the compensation time constant settings are too high, radius deviations are
compensated at quadrant transitions during circularity testing (on condition that the optimum
injection amplitude has already been calculated), but the deviation in the direction of the arc
center increases significantly after quadrant transitions.
Figure 5-25
Adaptation yes/no?
If, with the time constant and the constant injection amplitude determined, a good result is
achieved both in the circularity test and in positioning over the whole working area (i.e. for all
radii and velocities of relevance), curve adaptation will not be necessary.
However, if the friction compensation turns out to be dependent on the acceleration, the
adaptation characteristic must be calculated in second stage.
Commissioning stage 2: Friction compensation with adaptation
Application
Whenever friction compensation depends on the acceleration and the required results
cannot be obtained with constant injection amplitude, adaptation must be used.
In order to obtain optimum compensation over the whole of the working range of the friction
feedforward control where high demands are made on accuracy, the acceleration
dependency of the compensation value must be calculated. To achieve this, the dependency
must be measured at various points in the working range between acceleration zero and the
maximum planned acceleration. The adaptation characteristic derived from the
measurement results is then entered in the above machine data axis-specifically.
420
Compensation time constant too large
Function Manual, 03/2009, 6FC5397-1BP10-4BA0
Extended Functions