Reference Point Approach With Absolute Encoders; Reference Point Approach For Rotary Absolute Encoders With Equivalent Zero Mark - Siemens SINUMERIK 840D Function Manual

R1: Referencing
10.9 Referencing with absolute encoders
10.9.6

Reference point approach with absolute encoders

Parameter assignment
Traversing movement release
If for a machine axis with adjusted absolute value encoder as active measuring system,
reference point traversing is activated (manually in the JOG-REF mode or automatically via the
part program instruction G74), the machine axis travels depending on the parameterized
traversing movement release.
MD34330 $MA_REFP_STOP_AT_ABS_MARKER = <value>
Value Meaning
0
1
10.9.7

Reference point approach for rotary absolute encoders with equivalent zero mark

Function
To ensure that the reference point approach via zero mark (see Section "Referencing with
incremental measurement systems (Page 296)") can also be used with absolute encoders, the
zero mark, which is not provided in the hardware of absolute encoders, is simulated. For this,
the controller generates the signal for the equivalent zero mark once per encoder revolution,
always at the same position within the revolution.
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 10-1 Properties of incremental and absolute encoders
Property
Encoder type
Internal encoder position
Traversing range extension
328
Traversing is enabled.
When reference point approach is initiated, the machine axis moves to the reference point
position. When reaching the reference point position, the reference point approach is comple‐
ted.
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
Value is updated only in MD34210 ≥ 1
No effect
MD30240 $MA_ENC_TYPE =
1
MD30250 $MA_ACT_POS_ABS =
Value is updated only in MD30270 = 0
MD30270 $MA_ENC_ABS_BUFFERING =
Absolute encoder
4
= 0 (default): Active
Axes and spindles
Function Manual, 06/2019, A5E47437747B AA