Siemens SINUMERIK 840D sl Function Manual page 559

The actual position value supplied by the new motor encoder has no reference to the
mechanical system. This means that the absolute value encoder must be re-aligned and set-
up at this point.
Note
A safety acceptance report is generally not required after a motor has been replaced.
Re-calibration procedure
Note
After the NCK-Reset, the axis can be traversed again. Alarms 27000/C01797 "Axis not safely
referenced" are still active and indicate that the functions "safe limit positions" and "Safe Cams"
are not active in this state. For example, if the "safe limit positions" are to be used as a substitute
for hardware limit switches, then they are not functioning at this time!
1. Reset the NCK
2. Traverse the axis to the reference position, but first enter MD34010
$MA_REFP_CAM_DIR_IS_MINUS corresponding to the approach direction. (34010 should
be set to 1 if the axis is moved in the negative (minus) direction to the reference position.)
3. Set MD34100 $MA_REFP_SET_POS to the actual value of the reference position.
4. Set MD34210 $MA_ENC_REFP_STATE to 1 to activate calibration.
5. Select the axis that is to be calibrated on the machine control panel and press the RESET
key on the machine control panel.
6. Select the JOG/REF mode, enable the axis feed.
7. Corresponding to MD34010 REFP_CAM_DIR_IS_MINUS and the traversing direction to
the reference position, calibration should be started using the "+" or "–" traversing key
(backlash has been moved to through).
8. The axis does not traverse. Instead, the offset between the correct actual value (reference
position) and the actual value - supplied by the encoder - is entered in MD34090
$MA_REFP_MOVE_DIST_CORR. The actual value appears in the basic screen and the
axis signals "referenced". The value 2 is entered in MD34210 as result.
Example::
MD34010=1 (minus) and the reference position was approached in the negative (minus)
direction. This means that the "–" key must also be pressed on the machine control panel.
9. When the absolute value encoder has been recalibrated (MD34210 from 1 → 2), the axis
changes over into the "referenced" state. At this time, the new valid actual position is
accepted as the safe actual values (axis and drive).
10.Finally, with the JOG/REF machine mode active, on the HMI the "user agreement" softkey
must be pressed and the user agreement for the axis involved must be reset. Alarms 27000/
C01797 disappear and the functions "safe limit positions" and "Safe Cams" are safely active
again.
Safety Integrated
Function Manual, 12/2017, 6FC5397-4BP40-6BA1
Commissioning
10.7 Replacing a motor or encoder
559