Supplementary Conditions; Large Traverse Range - Siemens SINUMERIK 840D Function Manual

R1: Referencing

10.11 Supplementary conditions

10.11 Supplementary conditions
10.11.1

Large traverse range

Linear axes with a traversing range > 4096 encoder revolutions, rotatory absolute encoder
EQN 1325 and a parameterized absolute encoder range of
MD34220 $MA_ENC_ABS_TURNS_MODULO = 4096:
The maximum possible travel range corresponds to that of incremental encoders.
Endlessly turning rotary axes with absolute encoders:
● Any number of integer transmission ratios are permitted.
● We recommend that you parameterize endlessly turning rotary axes with absolute encoders
as modulo rotary axes (traversing range 0...360 degrees):
MD30310 $MA_ROT_IS_MODULO = 1
Otherwise, the rotary axis may require a very large traversing path to reach absolute zero
when the measuring system is activated.
Machine axes with absolute encoders:
In order that the controller correctly determines the current actual position after the restart of the
measuring system, the machine axis may only be moved less than half the absolute encoder
range when the measuring system is switched off:
MD34220 $MA_ENC_ABS_TURNS_MODULO
Notes on uniqueness of encoder positions
Note
Linear absolute encoders
The absolute value of linear position encoders, e.g. Heidenhain LC181, is always unique for the
scale lengths available.
Rotary absolute encoders
The absolute value of rotary absolute encoders is only unique within the range of the specific
maximum encoder revolutions.
For example, the EQN 1325 rotary absolute encoder by Heidenhain supplies a unique absolute
value in the range of 0 to 4,096 encoder revolutions.
Depending on how the encoder is connected that will result in:
● Rotary axis with encoder on load: 4096 load revolutions
● Rotary axis with encoder on motor: 4096 motor revolutions
● Linear axis with encoder on motor: 4096 motor revolutions
Example:
An EQN 1325 rotary absolute encoder is mounted on the motor of a linear axis. For an effective
leadscrew pitch of 10 mm this will result in a unique absolute value within the travel range
-20.48 to +20.48 m.
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Axes and spindles
Function Manual, 06/2019, A5E47437747B AA