Siemens SINUMERIK 840C Installation Instructions Manual page 742

10 Axis and Spindle Installation 09.95
10.5.1 Open-loop control mode
Gear ratio changing
Gear ratio changing is only possible in the open-loop control mode. There can be up to eight
different ratios between motor and spindle.
A permitted range of speed can be laid down for each gear ratio by defining maximum and
minimum speed values. If the speed setpoint does not fall within the range of the gear ratio
that is currently active, the number of the required gear ratio is ascertained automatically and
entered into the interface to the PLC together with IS:CHANGE GEAR.
The PLC user program executes the gear change, acknowledges the request by resetting IS:
CHANGE GEAR and enters the new gear ratio into the interface.
If no suitable gear ratio for the programmed speed exists, no request for gear changing is
generated. The programmed speed is then transferred to the current gear ratio. So it is
important to ensure that there is always a suitable gear ratio available.
The behaviour of the spindle during gear ratio changing can be influenced by MD 521*, bit 5
"New S value after PLC acknowledgement". If the bit is set, the programmed speed setpoint
will only be accepted when the PLC has acknowledged gear ratio changing. This prevents an
unwanted increase in speed while still in the old ratio before changeover.
Voltage [volts]
MD 4030 MD 4040
MD 4050
10
MD 4480
Speed [rev/min]
MD 4110 MD 4130
MD 4120
The gear is output on the basis of the lowest switching frequency, i.e. if the speeds of the
individual gears overlap, a new gear is output only when the programmed S value is no longer
possible for the selected gear.
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SINUMERIK 840C (IA)