Siemens SINUMERIK 840C - Manual (Page 944)

01.99 12 Functional Descriptions
12.18.14 Special cases of gearbox interpolation
• Gear stage switchover and the transfer of new actual gear stages are not possible in
synchronous operation.
Synchronous spindle in mechanically coupled operation
When a pair of synchronous spindles is operated with clamped workpiece, certain factors
including
• the rigidity of the workpiece
• the closing force of the chuck and
• the stiffness of the drive mechanical components
cause backlash via the workpiece.
These effects can cause shutdown of the drive both at standstill and in dynamic operation.
Dynamic:
During acceleration in mechanically coupled operation, asymmetries in the control loop
concerned may cause very strong torque deviations to develop between the individual
spindles, leading to an imbalance in power distribution, i.e. one drive takes over or carries the
main load.
Static:
When a workpiece is transferred to the following drive, an angular offset may develop between
the leading and following drives as a result of the mechanical closing action of the chuck .
Provided that both drives are coupled via the workpiece,
• this offset cannot be corrected or eliminated
• the workpiece may be strained by torsional forces or
• the workpiece may be damaged by the chuck.
The following procedure is recommended:
Position controller level
Dynamic:
Asymmetry between the control loops involved can be corrected via setpoint filters.
Static:
The angular offset which develops, for example, when the chuck closes, causes straining on
intervention by the position control/compensatory controller. This type of strain can be
prevented by means of the interface signal "Follow up synchronism deviation".
Speed controller level
When SIMODRIVE 611A/D and 1FT drive systems are used, a so-called integrator feedback
can be activated in the speed controller. The feedback function does not lead to integration of
the torques by the I-action component at low speeds.
When main spindle drives are used, it is necessary - depending on prevailing conditions - to
deactivate at least the I-action component of the following axis speed controller, particularly in
static operation.
Note:
With synchronous spindles avoid rigid linking as this may possibly lead to running off of the
spindle/axis during automatically controlled correction.
NC MD 1432*/495*: At the initial setting ”automatically controlled correction” is always selected
(16 seconds).
© Siemens AG 1992 All Rights Reserved 6FC5197- AA50 12–169
SINUMERIK 840C (IA)