Siemens SINUMERIK 840D sl Function Manual page 348

Compensations (K3)
5.3 Backlash compensation
2nd measuring system
If there is a 2nd measuring system for the axis/spindle, a backlash compensation must be
entered for this too. As the second measuring system is mounted in a different way from the
first measuring system, the backlash can be different from that of the first measuring system.
When the measuring system is switched over the associated compensation value is always
activated.
Large backlash compensation
The user has the option of applying the backlash compensation value gradually in several
increments when the relevant axis reverses direction. This prevents a setpoint step change
on the axes from causing corresponding errors.
The contents of the axis-specific machine data:
MD36500 $MA_ENC_CHANGE_TOL (Max. tolerance on position actual value switchover)
determines the increment with which the backlash compensation value (MD 32450) is
applied.
Please note that the backlash compensation is fully calculated only after n servo cycles
(n = MD32450 / MD36500). An excessive time span can cause the triggering of a zero speed
monitoring alarm.
If the setting in machine data:
MD36500 $MA_ENC_CHANGE_TOL (Max. tolerance on position actual value switchover)
is higher than the setting in:
MD32450 $MA_BACKLASH,
the compensation is performed in one servo cycle.
348
Function Manual, 01/2008, 6FC5397-1BP10-3BA0
Extended Functions