Siemens SINUMERIK 840D sl Function Manual page 1570

Detailed description
2.4 Referencing with incremental measurement systems
2.4.5 Buffered actual value
Automatic referencing
By buffering the actual value, "automatic referencing" is enabled, which does not require
machine axes with incremental measuring systems, after situations in which they are in the
"Not referenced" condition, to traverse back to the reference point for referencing of the
measuring system. For example, this is the case after:
• POWER OFF/ON
• "Parking" selected:
If the function is active, referencing is performed without axis motion by synchronizing the
actual value system of the machine axis to the last valid actual value. The actual value is
buffered in a retentive memory area of the control even after POWER OFF.
Warning
During the time in which the measuring system (encoder) of the machine axis is switched off
((POWER OFF, "Parking" the axis, etc.), the machine axis may not be further mechanically
moved. This must be supported by the machine manufacturer with such measures as
holding brakes, etc., and ensured by the user. Otherwise the actual value system of the
machine axis will no longer be synchronized resulting in danger to personnel and machine.
Precondition for automatic referencing
At the time of automatic referencing (e.g. after POWER ON, "Parking" of the machine axis is
again deselected, etc.), the encoder status of the active measuring system of the machine
axis must have the value 2.
MD34210 $MA_ENC_REFP_STATE = 2
That is, the encoder is referenced, an exact stop is reached, and automatic referencing is
active the next time the encoder is activated.
The following conditions must be fulfilled:
• "Automatic referencing" is assigned for the measuring system (encoder):
Encoder status =
1:
24
DB31, ... DBX1.5 / 1.6 (Position measuring system 1/2) = 0
DB31, ... DBX2.1 (servo enable) = 0
MD34210 $MA_ENC_REFP_STATE = 1
Automatic referencing enabled, but encoder not yet referenced or
exact stop not reached.
Basic logic functions: Reference Point Approach (R1)
Function Manual, 11/2006, 6FC5397-0BP10-2BA0