Reference Point Approach With Absolute Encoders; Reference Point Approach In Rotary Absolute Encoders With External Zero Mark - Siemens SINUMERIK 840D sl Function Manual

R1: Referencing
15.9 Referencing with absolute encoders
15.9.6

Reference point approach with absolute encoders

Traversing movement release
If for a mchine axis with adjusted absolute value encoder as active measuring system,
reference point traversing is activated (manual in the mode JOG-REF or automatic according
to part program instruction G74), the machine axis travels depending on the parameterized
release traversing movement.
MD34330 $MA_REFP_STOP_AT_ABS_MARKER = <Value>
Value
0
1
15.9.7

Reference point approach in rotary absolute encoders with external zero mark

Function
To be able to use the reference point approach with a zero mark, as is usual in incremental
encoders (refer to Section "Referencing with incremental measurement systems
(Page 1154)"), also with absolute encoders, the missing HW zero marks are created in software
form once every encoder revolution, always at the same position within the rotation.
Difference compared to referencing with incremental encoders
An absolute encoder with replacement zero mark should not be considerd as a complete
equivalent of an incremental encoder. All the properties of the absolute encoder are retained.
The following table lists the different properties of incremental and absolute encoders:
Table 15-1 Properties of incremental and absolute encoders
Property
Encoder type
Internal encoder position
Traversing range extension
Reference point offset
1186
Meaning
Traversing is enabled.
When reference point approach is initiated, the machine axis moves to the reference point
position. Reference point approach is completed when the reference point position is reached.
Traversing is not enabled.
After the activation of the reference point travel, the machine axis does not travel and the
reference point travel is immediately completed.
Incremental encoder
= 1
Value is updated only in MD34210 ≥ 1
No effect
Value input allowed
Absolute encoder
MD30240 $MA_ENC_TYPE
= 4
MD30250 $MA_ACT_POS_ABS
Value is updated only in MD30270 = 0
MD30270 $MA_ENC_ABS_BUFFERING
= 0 (default): Active
MD34090 $MA_REFP_MOVE_DIST_CORR
Value is updated exclusively via control
Function Manual, 01/2015, 6FC5397-0BP40-5BA2
Basic Functions