Siemens SINUMERIK 828D Function Manual page 1240

R1: Reference point approach
15.9 Referencing with absolute value encoders
Part program
The part program for automatic adjustment of absolute encoders with probe must perform the points listed below
for each axis in the order indicated:
1. Approach the adjustment position of machine axis, which is detected from the probe response.
The position must be approached several times from the same direction, but at a velocity which is gradually
reduced on each approach, to ensure that the measured value obtained is as accurate as possible. The
measured value is stored in system variable $AA_IM.
2. Calculating and writing the reference point offset:
3. Set the absolute encoder status to "Encoder is adjusted":
MD34210 $MA_ ENC_REFP_STATE = 2
Sequence
Proceed as follows for automatic adjustment with probe:
1. Enable part program start even for non-referenced machine axes:
MD20700 $MC_REFP_NC_START_LOCK = 0
2. Enter the machine axis position relative to machine zero when probe is switched as the reference point value
for all relevant machine axes:
MD34100 $MA_REFP_SET_POS = reference point value
3. Activate NCK-Reset for the acceptance of the entered machine data values.
4. Start part program.
5. After completion of the part program, re-secure the partial program start for machine axes which are not
referenced:
MD20700 $MC_REFP_NC_START_LOCK = 1
6. Initiate POWER ON - Reset so that the reference point offset written by the part program is permanently
active:
MD34090 $MA_REFP_MOVE_DIST_CORR (reference point offset)
Note
Activate reference point offset permanently
The entered reference point offset (MD34090) will only be permanently active after
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).
1240
Function Manual, 09/2011, 6FC5397-0BP40-2BA0
Basic Functions