Siemens SINUMERIK 840D Function Manual page 306

R1: Referencing
10.5 Referencing with incremental measurement systems
● Cycle time for updating the NC/PLC interface
● Interpolator clock cycle
● Position control cycle
Notes on setting
● Reference cam
Aligning the signal edge of the reference cam directly between two zero marks has proven
to be the most practical method.
● Electronic reference cam shift
Information needed for parameterizing the electronic reference cam shift is to be found in
the read-only machine data:
MD34093 $MA_REFP_CAM_MARKER_DIST (distance between reference cam/reference
mark)
The indicated value is equivalent to the distance between departure from the reference cam
and detection of the reference mark. If the values are too small, there is a risk that the
determination of the reference point will be non-deterministic, due to temperature effects or
fluctuations in the operating time of the cam signal.
Phase 2: Properties
● Feedrate override is not active.
Traversing is performed internally with feedrate override = 100%.
If a feedrate override of 0% is specified, an abort occurs.
● Feed stop (channel-specific and axis-specific) is active.
● NC stop and NC start are not active.
● If the machine axis does not arrive at Phase 2 within the parameterized distance of the
reference mark (encoder zero mark), the machine axis will be stopped:
MD34060 $MA_REFP_MAX_ MARKER_DIST (max. distance to the reference mark)
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WARNING
Risk of collision
If the reference cam adjustment is faulty or inaccurate, an incorrect zero mark can be
evaluated. The controller then calculates an incorrect machine zero. As a result, the
machine axis will approach the wrong positions. Software limit switches, protected areas
and working area limitations act on incorrect positions and are therefore incapable of
protecting the machine. The path difference is +/- of the path covered by the machine axis
between two zero marks.
Axes and spindles
Function Manual, 06/2019, A5E47437747B AA