Referencing; Referencing Methods - Siemens SINAMICS G120D Original Instructions Manual

8.6.7

Referencing

8.6.7.1

Referencing methods

Overview
If you are using an incremental encoder for the position actual value, after the supply voltage
is switched off, the converter loses its valid position actual value. After the supply voltage is
switched on again, the converter no longer knows the reference of the axis position to the
machine.
Referencing re-establishes the reference between the zero point of the position calculated in
the converter and the machine zero point.
Absolute encoders retain their position information, even after the supply has been switched
off.
The converter offers various ways of referencing the axis:
● Reference point approach - only with incremental encoders
● Flying referencing - with all encoder types
● Set reference point - with all encoder types
● Absolute encoder adjustment - with absolute encoders
Reference point approach
The converter automatically traverses the axis to a defined reference point.
Example: A workpiece must be positioned at a
starting point before machining starts.
Flying referencing
The converter corrects its position actual value while traversing and reduces errors, e.g.
caused by wheel slip or a gear ratio that has not been precisely set.
Example: A pallet on a roller conveyor must be stopped at a specific position. However, the
exact position of the pallet on the conveyor is only known when a sensor is passed.
Figure 8-25
Set the reference point and adjust the absolute encoder
The converter takes the reference point coordinate as the new axis position.
Converter with control units CU250D-2
Operating Instructions, 04/2014, FW V4.7, A5E34261542B AA
Positioning an item to be transported on a roller conveyor
8.6 Basic positioner and position control
Setting functions
169