Siemens SINUMERIK 828D Function Manual page 1223

Rotary measuring system
For rotary measuring systems, the same applies as for linear measuring systems (see above).
Determining the absolute offset
The following procedure is recommended for the determination of the absolute offset between the machine zero
point and the position of the first reference mark of a machine axis:
1. Enter the value zero for the absolute offset:
MD34090 $MA_REFP_MOVE_DIST_CORR = 0
2. Perform reference point approach.
Note:Reference point approach should be performed at a point in the machine where the exact position of the
machine axis relative to machine zero can be determined easily with a laser interferometer, for example.
3. Determine the actual position of the machine axis via the operator interface screen.
4. Measure the current position of the machine axis with reference to the machine zero point.
5. Calculate absolute offset and enter in MD34090.
The absolute offset is calculated with respect to the machine coordinate system and depending on the orientation
of the measuring system (equidirectional or inverse) as:
Orientation of the measuring system
equidirectional
Opposite direction
After determining the absolute offset and the entry in MD34090, the reference point
traversing for the machine axis must be carried out once more.
Referencing methods
Referencing with distance-coded reference marks can be performed in one of two ways:
• Evaluation of two consecutive reference marks:
MD34200 $MA_ENC_REFP_MODE (referencing mode) = 3
Advantage:
- Short travel path
• Evaluation of four consecutive reference marks:
MD34200 $MA_ENC_REFP_MODE = 8
Advantage:
- Plausibility check by NC is possible
- Increase in reliability of referencing result
Basic Functions
Function Manual, 09/2011, 6FC5397-0BP40-2BA0
Absolute offset
Measured position + displayed actual position
Measured position - displayed actual position
WARNING
15.6 Referencing with distance­coded reference marks
R1: Reference point approach
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