Siemens SINUMERIK 840D Function Manual page 324

R1: Referencing
10.9 Referencing with absolute encoders
This determined position value will be made known to the NC as the reference point value. The
NC then calculates the reference point offset from the difference between the encoder absolute
value and the reference point value.
Procedure
1. Check whether the referencing mode is set to "Assume the reference point value":
MD34200 $MA_ENC_REFP_MODE == 0
If not, enter the value 0 in the machine and trigger a Power On reset.
2. Traverse the machine axis in JOG mode to the position to be measured (e.g. with a laser
interferometer) or to a known position (e.g. fixed stop).
Note
The machine axis can only be traversed in the direction enabled for referencing with the
travel keys:
MD34010 $MA_REFP_CAM_DIR_IS_MINUS (approach reference point in minus direction)
To avoid an invalid position because of backlash in the drive train, the known position must
be approached at low velocity.
3. Enter the position of the machine axis relative to machine zero as the reference point value
in the machine data:
MD34100 $MA_REFP_SET_POS =
4. Enable encoder adjustment:
MD34210 $MA_ENC_REFP_STATE = 1
5. Trigger a Power On reset for acceptance of the entered machine data values.
6. Switch to JOG-REF mode.
324
Position
Function Manual, 06/2019, A5E47437747B AA
Axes and spindles