Siemens sinumerik 840D sl Function Manual page 143

Referencing and synchronization of gantry axes
As the example "Gantry-type milling machine" shows, the forced coupling between gantry
axes must remain intact in all operating modes as well as immediately after power ON. In
cases where an incremental measuring system is being used for the leading or the
synchronized axis, the reference point must be approached while maintaining the axis
coupling immediately after machine power ON.
After every axis in the gantry grouping has approached its reference point, any misalignment
that may exist between the axes must be eliminated (this is known as the gantry
synchronization process). As soon as this occurs, the following interface signal will be
signaled to the PLC:
DB31, ... DBX101.5 (gantry grouping is synchronized)
The operational sequence for referencing and synchronizing gantry axes is described in
detail under the topic "Referencing and synchronizing of gantry axes".
Closed-loop control
The dynamic control response settings of the coupled gantry axes must be identical (see
topic "Starting up gantry axes"). This ensures that in normal operation, the leading and
synchronized axes move in positional synchronism even during acceleration and braking.
Load effects are compensated by the appropriate drive of the leading or synchronized axis.
Disturbance characteristic
When a disturbance occurs which causes shutdown of one gantry axis owing, for example,
to cancellation of the controller enabling signal (example: EMERGENCY STOP), all other
coupled gantry axes are also shut down.
Separation of forced coupling
In certain situations (e.g. one gantry axis is no longer referenced owing to an encoder
failure), it may be necessary to correct or reduce the misalignment between the gantry axes
prior to referencing. To do this, it must be possible to traverse the leading or the
synchronized axis manually in the uncoupled state.
The forced coupling between the gantry axes can be separated by means of the following
MD setting and subsequent RESET:
MD37140 $MA_GANTRY_BREAK_UP = 1 (invalidate gantry grouping)
The gantry axes can then be traversed separately by hand; the monitoring of the warning
and trip limits is not operative in this state.
Caution
If the gantry axes remain mechanically coupled, there is a risk of damage to the machine
when the leading or synchronized axes are traversed in this operating state!
Special functions: Gantry Axes (G1)
Function Manual, 11/2006, 6FC5397-2BP10-2BA0
Detailed description
2.1 "Gantry axes" function
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