794 HEIDENHAIN Technical Manual MANUALplus 620
6.15.3 Traversing the reference marks
The reference marks must be traversed after any interruption in power.
Specify which axes are homed, and in which sequence, in MP_refAllAxes or
MP_refAxis.
After acknowledging the power interruption with the CE key or pressing the
Control voltage On key, you can preselect individual axes to be homed or
use the ALL soft key.
After the NC start key has been pressed, the axes are homed one after the
other in the sequence defined in parameter MP_refAxis.
After the reference marks have been traversed:
The software limit switches are activated.
The most recently set datum or workpiece datum and the machine datum
are reproduced.
Distance between
the scale reference
point and the
machine datum
For position encoders with distance-coded reference marks, the machine
datum is defined with respect to the scale reference point, which is at the first
reference mark after the beginning of the measuring length. On angle
encoders, the scale reference point is marked:
In MP_refPosition, enter the distance between the scale reference point
and the machine datum.
For position encoders without distance-coded reference marks but with more
than one reference mark, every reference mark to be traversed must be
evaluated.
For each reference mark to be traversed, create another parameter set, and
enter in MP_refPosition the distance between the scale reference point and
the reference mark.
Activate the parameter set that corresponds to the traversed reference
mark.
Assigning a
reference value
In some cases it may be necessary to assign a new reference value to an axis,
e.g. if an axis is mechanically fixed and the encoder is moved. A typical
application is, for example, with (Hirth) clamped axes
Since due to the mechanical fixing the position of the axis cannot be changed,
you can assign it a new reference value.
Enter the new reference value in Module 9147.
Please note the following restriction if you are using the CC 422 controller
unit:
If you are using Module 9147, the following settings in the MP_refType
parameter (functional sequence for traversing the reference marks) are not
permissible when using the CC 422:
MP_refType = distance coded + on the fly
MP_refType = without switch + on the fly
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