Siemens SINUMERIK 840D sl Function Manual page 163

Synchronizing gantry axes
The gantry synchronization is activated via the NC/PLC interface signal (see Section
"Referencing and synchronization of gantry axes (Page 148)"):
DB31, ... DBX29.4 = 1 (start synchronization of gantry)
The completion of the synchronization is displayed via the NC/PLC interface signal:
DB31, ... DBX101.5 == 1 (gantry grouping is synchronous)
Once the axes have been synchronized, check that the dimensional offset between the guide
and the synchronous axes is 0. If required, make corrections in the machine data mentioned
above.
Input of gantry warning limit
Once the reference point values for the guide and synchronous axes have been optimized so
that the gantry axes are perfectly aligned with one another after synchronization, the warning
limit values for all axes must be entered in the following machine data:
MD37110 $MA_GANTRY_POS_TOL_WARNING (gantry warning limit)
To do this, the value must be increased incrementally until it is just below the alarm (limit
exceeded) response limit. It is particularly important to check the acceleration phases.
This limit value also determines the position deviation value at which gantry synchronization
is automatically started in the control.
Calculating and activating compensations
In cases where the gantry axes require compensation (backlash, sag, temperature or
leadscrew error), the compensation values for the guide axis and the synchronous axis must
be calculated and entered in the appropriate parameters or tables.
References
Extended Functions Function Manual; Compensations (K3)
Function generator / measuring function
The activation of the function generator and measuring function for a synchronous axis is
aborted with an error message. If an activation of the synchronous axis is absolutely necessary,
e.g. to measure the machine, the guide and the synchronous axes must be temporarily
interchanged.
Special cases
If individual axes have to be activated, the gantry groups must be temporarily canceled. As
the second axis no longer travels in synchronism with the first axis, the activated axis must not
be allowed to traverse beyond the positional tolerance.
Special functions
Function Manual, 01/2015, 6FC5397-2BP40-5BA2
G1: Gantry axes
3.4 Start-up of gantry axes
163