Siemens SINUMERIK 840D Function Manual page 272

G1: Gantry axes
9.3 Referencing and synchronization of gantry axes
MD36500 $MA_ENC_CHANGE_TOL (Max. tolerance for position actual value switchover)
The two position measuring systems must, however, have been referenced beforehand. The
relevant measuring system must be selected before referencing is initiated. The operational
sequence is then the same as that described above.
Channelspecific referencing
Gantry axes can also be referenced by channel with the following interface signal:
DB21, ... DBX1.0 (activate referencing)
The value of the leading axis' machine data is used for the axis sequence for channel-specific
referencing:
MD34110 $MA_REFP_CYCLE_NR (Axis sequence for channel-specific referencing)
After the reference point of the leading axis has been reached, the synchronized axes are
referenced first as described above.
Referencing from part program with G74
The referencing and synchronization process for gantry axes can also be initiated from the part
program by means of command G74. In this case, only the axis name of the leading axis may
be programmed. The operational sequence is analogous to that described for axis-specific
referencing.
Position measuring system with distancecoded reference marks
In order that reference point approach operations do not have to travel through large distances,
it is possible to use just one position measuring system - or a position measuring system as 2nd
measuring system with distance-coded reference marks for gantry axes. In this way the
measuring system is referenced after traversal of a short path (e.g. 20 mm). The procedure for
referencing the gantry axes is the same as that described for the normal incremental measuring
system.
Further information:
R1: Referencing (Page 291)
Absolute encoder
During the course of the synchronization compensatory motion, all axes in the gantry axis
grouping traverse to the reference point value of the leading axis defined in the machine data:
MD34100 $MA_REFP_SET_POS (reference point value/destination point for distancecoded
system)
The absolute encoders and distanced-coded encoders of the leading axis will be set to the
current actual position of the leading axis or to the reference point by the following machine
data:
MD34330 $MA_REFP_STOP_AT_ABS_MARKER (Distancecoded linear measuring system
without destination point)
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Axes and spindles
Function Manual, 06/2019, A5E47437747B AA