Siemens SINUMERIK 840D sl Function Manual page 344

G2: Velocities, setpoint / actual value systems, closed-loop control
7.4 Setpoint/actual-value system
Power tools generally have their "own" intermediate gear. Such variable mechanics can be
configured by multiplying the active intermediate gearbox and the motor/load gearbox.
Different gearbox transmission ratios for switching
Unlike the motor/load gear, there is no parameter set for the intermediate gear and, therefore,
no way of controlling the time-synchronized switchover to the part program or PLC (NC/PLC
interface). Part programming during gear change is, therefore, ruled out. It remains the task
of the user to match the synchronization of the relevant changed machine data to the
corresponding mechanical switchover and activate it. On switchover during a motion,
compensations cannot be ruled out due to jumps in the scaling factors. These are not
monitored for violation of the maximum acceleration.
Encoder directly at the tool
Another connection option is possible for a "tool-side encoder" on the intermediate gear, by
configuring machine data:
MD31044 $MA_ENC_IS_DIRECT2
Encoder not directly at the tool
The following supplementary conditions apply to a gear change of the intermediate gear in
position-control mode:
● The gear ratio to be changed is incorporated in a re-scaling of the encoder information in
this case.
In this case, the following applies to axes/spindles in positioning mode:
● A non-abrupt gear change is only possible at zero speed.
To do this, the tool-side position before and after a gear change are set equal for a change
in the ratio, since the mechanical position does not (or hardly) change during a gear stage
change.
Recommendation:
To avoid 21612 "Controller enable reset during motion", changeover should be carried out
"only at zero speed". It is still permissible and expedient to switch the axis or spindle to
speed-control or follow-up mode before or during a gear change.
Boundary conditions
If the encoder to be used for position control is connected directly at the tool, the gear stage
change only affects the physical quantities at the speed interface between the NC and the
drive of the motor/load gear. The internal parameter sets are not changed.
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CAUTION
Function Manual, 01/2015, 6FC5397-0BP40-5BA2
Basic Functions