Siemens SINUMERIK 840D Function Manual page 409

Dimension system metric/inch
With the setting:
MD10260 CONVERT_SCALING_SYSTEM = 1
, the cam positions no longer refer to the configured basic dimension system, but to the
dimension system set in the following machine data:
MD10270 POS_TAB_SCALING_SYSTEM (measuring system of position tables)
Value
0
1
MD10270 therefore defines the dimension system for position data from setting data SD41500
... SD41507.
A switchover with G70/G71 or G700/G710 has no effect.
Sensing of cam positions
To set the cam signals, the actual position of the axes is compared to the cam position.
Writing/reading of cam positions
The setting data can be read and written via HMI, PLC and part program.
Accesses from the part program are not synchronous to machining.
Synchronization can only be achieved by means of a programmed block preprocessing stop
(STOPRE command).
It is possible to read and write the cam positions with FB2 and FB3 in the PLC user program.
Axis/cam assignment
A cam pair is assigned to a machine axis using the general machine data:
MD10450 SW_CAM_ASSIGN_TAB[n] (assignment of software cams to machine axes)
Note
Changes to an axis assignment take effect after the next NC power-up.
Cam pairs to which no axis is assigned are not active.
A cam pair can only be assigned to one machine axis at a time.
Several cam pairs can be defined for one machine axis.
Axes and spindles
Function Manual, 06/2019, A5E47437747B AA
Meaning
Metric
inch
N3: Software cams, position switching signals
13.2 Cam signals and cam positions
409