Siemens SINUMERIK 840D sl Function Manual page 327

When workpieces are transferred from front to rear machining, a position offset may result
from the closing of the workpiece receptacle. This could be down to square-edged
workpieces or due to the generation of an angular momentum when the workpiece receptacle
(chuck) is closed quickly during a movement. Depending on the resistance of the workpiece,
the tension can be detected by means of an increase in the current consumption of both the
motors involved in the coupling and/or by means of the workpiece being subjected to torsion.
This could lead to the following NC/PLC interface signals being reset, according to the
synchronism tolerance which has been set, and the magnitude of the offset:
DB31, ... DBX98.1 (coarse synchronism) and/or
DB31, ... DBX98.0 (fine synchronism)
For the setpoint coupling, the position and velocity setpoints are calculated precisely in
accordance with the programmed coupling rule and output to the Control Units. If identical
drives and a rigid workpiece are used, this will lead to a regulative deviation at the leading and
following spindle, half due to a setpoint difference and half due to an actual value difference.
Function
The "track the deviation from synchronism" function serves to detect the position offset which
has been imposed on the actual value and to correct the following spindle when calculating
the setpoint.
Requirements
A coupling closed via the part/chuck must be in place in order to use this function.
Versions
There are two different options for determining the deviation from synchronism:
1. The deviation from synchronism is determined by the NCK.
→ See "Measuring the deviation from synchronism [Page 328]"
2. The deviation value is already known and entered by the user directly.
→ See "Entering the deviation from synchronism directly [Page 330]"
In both cases, the deviation value is then incorporated into the setpoint value calculation for
the following spindle, as a correction value.
Availability
The "track the deviation from synchronism" function was developed for machine couplings
(CPFRS="machine"). This means that it is also available for the "synchronous spindle"
coupling type (CPSETTYPE="COUP").
Special Functions
Function Manual, 09/2011, 6FC5397-2BP40-2BA0
M3: Coupled axes
5.5 Generic coupling
327