Siemens SINUMERIK 840D Function Manual page 319

Zero mark selection when several zero mark signals occur
If several encoder zero marks are detected in the traversing range of the machine axis due to
machine-specific factors, e.g. reduction gear between encoder and load, a proximity switch
must be mounted on the machine and connected via a digital input of the NCU interface in order
to clearly determine the reference point.
Note
Contact-less proximity switch signal: Zero mark selection
The processing of the proximity switch signal is performed exclusively in the drive. Connection
and parameterization, see Section "Hardware signals (Page 296)".
Enable
The "Referencing in follow-up mode" function is enabled with:
MD34104 $MA_REFP_PERMITTED_IN_FOLLOWUP = TRUE
Starting the referencing operation
If the machine axis is in follow-up mode (DB31, ... DBX61.3 == TRUE) at the start of reference
point approach, the measuring system is referenced in follow-up mode.
If the machine axis is not operating in the follow-up mode at the start of reference point
traversing, the "normal" from the NC-controlled reference point travels is carried out.
Referencing in follow-up mode can be started in the following modes:
● JOG-REF: Traversing keys
● AUTOMATIC: Part program command G74
Sequence of the referencing operation (JOG-REF mode)
1. Activate follow-up mode of machine axis:
DB31, ... DBX1.4 (follow-up mode) = 1
DB31, ... DBX2.1 (controller enable) = 0
2. Wait for activation of follow-up mode:
DB31, ... DBX61.3 (follow-up active) == 1
3. Switch to JOG mode, REF machine function
4. External motion of machine axis across encoder zero mark or parameterized number of
distance-coded reference marks. The referencing operation is started internally in the NC
as soon as the machine axis is moved: The following NC/PLC interface signal is reset as
feedback:
DB31, ... DBX61.4 (axis/spindle stationary) == 0
5. The measuring system is referenced after the encoder zero mark or the assigned number
of distance-coded reference marks have been successfully detected: The following NC/
PLC interface signal is set as feedback:
DB31, ... DBX60.4/60.5 (referenced/synchronized 1/2) == 1
Axes and spindles
Function Manual, 06/2019, A5E47437747B AA
R1: Referencing
10.8 Referencing in follow-up mode
319