Siemens SINUMERIK 840D sl Function Manual page 1583

2.6.3 Adjustment by entering a reference point value
Function
During adjustment by entering the reference point value, the absolute position of the
machine axis with reference to the machine zero point is determined by e.g.:
• Position measurement (e.g. laser interferometer)
• Moving the machine axis to a known position (e.g. fixed stop)
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.
Basic logic functions: Reference Point Approach (R1)
Function Manual, 11/2006, 6FC5397-0BP10-2BA0
Note
Backlash compensation
If backlash compensation is parameterized for a measuring system with absolute value
encoder, the following must be observed:
No backlash is permitted during machine axis travel to the adjusted machine position.
Activate reference point offset permanently
The entered reference point offset (MD34090) will be permanently active only after initial
POWER ON - Reset. If the machine axis is moved after the absolute encoder adjustment
without an interim POWER ON - Reset, the reference point offset entered in the machine
data can be overwritten, for example, as part of internal overrun offset.
Checking the actual position
Following adjustment of the absolute encoder, we recommend that you verify the actual
position of the machine axis the next time you power up the controller (POWER ON).
2.6 Referencing with absolute value encoders
Detailed description
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