Siemens SINUMERIK 840Di Function Manual page 409

Intermediate gear
Additional, configurable load intermediate gears are also supported by the control:
MD31066 $MA_DRIVE_AX_RATIO2_NUMERA (intermediate gear numerator)
MD31064 $MA_DRIVE_AX_RATIO2_DENOM (intermediate gear denominator)
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.
Caution
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 parts program or PLC
(VDI 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 movement,
compensations cannot be ruled out due to jumps in the scaling factors. These are not
monitored for violation of the maximum acceleration.
Encoder directly on 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 on 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
In this case, the following applies to axes/spindles in positioning mode:
• A non-abrupt gear change is only possible at zero speed.
Velocities, Setpoint/Actual-Value Systems, Closed-Loop Control (G2)
Function Manual, 08/2005 Edition, 6FC5397-0BP10-0BA0
this case.
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) changes 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.
Detailed Description
2.3 Setpoint/actual-value system
2-35