Siemens SINUMERIK 840Di Function Manual page 1896

Detailed Description
2.1 Various interface signals and functions (A2)
DB31, ...
DBX1.5 - DBX1.6 Position measuring system 1 (PMS1)/Position measuring system 2 (PMS2)
Application
1. Changing over from position measuring system 1 to positioning measuring system 2 (and vice
example(s)
2. Parking axis (i.e. no PMS is active):
3. Switch-off measuring system:
4. Reference point approach:
Special cases, If the state "parking axis" is active, the interface signal:
errors, .... DB31, ... DBX60.4/60.5 (referenced/synchronized 1/2)
is ignored at NC start for this axis.
Corresponding to .... DB31, ... DBX60.4 (referenced/synchronized 1)
DB31, ... DBX60.5 (referenced/synchronized 2)
DB31, ... DBX61.6 (speed controller active)
DB31, ... DBX2.1 (controller enable)
MD36500 $MA_ENC_CHANGE_TOL (max. tolerance on position actual value switchover)
MD30200 $MA_NUM_ENCS (number of encoders)
Additional references /FB1/ Description of Functions, Basic machine; Velocities, Setpoint-Actual Value Systems, Closed-
Loop Control (G2)
2-32
versa).
If the axis in both position measuring systems was referenced and the limit frequency of the
measured value encoder has not been exceeded in the meantime i.e.
DB31, ... DBX60.4 and 60.5 (referenced/synchronized 1 and 2) has signal state 1,
then after the changeover, a reference point approach does not have to be repeated.
On switchover, the current difference between position measuring system 1 and 2 is traversed
immediately.
With the machine data:
MD36500 $MA_ENC_CHANGE_TOL (maximum tolerance on position actual value
changeover)
a tolerance bandwidth can be entered - the deviation between the two actual values may lie
within this bandwidth when changing over.
If the actual value difference is greater than the tolerance, a switchover between the two
systems does not take place and alarm 25100 "Measuring system switchover" not possible is
triggered.
If the encoder has to be removed - e.g. if a rotary table has to be removed from the machine -
the position measuring system monitoring is switched off in the parking position.
The mounted axis/spindle encoder turns so quickly in certain applications that it can no longer
maintain its electrical characteristics (edge rate-of-rise, etc.).
When measuring system 1 or 2 is switched off the associated interface signal:
DB31, ... DBX60.4/60.5 (referenced/synchronized 1/2)
is reset.
Reference point approach of the axis is executed with the selected position measuring system.
Every PMS must be separately referenced.
NC/PLC Interface Signals (Z1)
Function Manual, 08/2005 Edition, 6FC5397-0BP10-0BA0