HEIDENHAIN TNC 155 W - Software Limit Switches

3.6.4 Traversing over distance-coded reference marks
If the linear transducers have distance-coded reference marks, (section 2.3.2) the traversing procedure for
“passing over the reference marks” is considerably short. Regardless of the position in which the machine
axis may be, the TNC 151 B/TNC 155 B can compute the absolute position after passing over the second
reference mark, i.e. after a maximum traverse of only 20 mm.
Caution:
When using linear transducers with distance-coded reference marks, the contact for “reference end position”
is open.
Both linear transducers with conventional or distance-coded reference marks can be connected to the
TNC 151 B/TNC 155 B. For instance, during machining a traverse of 20 mm can be insufficient in a
tool-axis to clear the tool for the reference mark routine after a power interruption.
It is, of course, Ipossible to pass over the reference mark with a manual traverse after entering the appropriate
code number.
3.6.5 Special sequence for reference point approach
The special sequence for reference point approach is only required when several reference points are located
within the machine traverses (e.g. wehn using rotary encoders as transducers) and no additional trip dogs
for “reference pulse inhibit” are being used (input J6 contacts 1,2, 3, 4 with A-Version), (inputs J4 contacts
5, 6, 7, 8 with P-version).
If machine parameter 69 is programmed with “1” the special sequence is active as follows:
Axes which are standing within the vicinity of the reference end position are backed-off from the reference
end position cam before approaching the reference points. The appropriate axes are designated by the
inverted display “reference point X/Y/Z/IV approach” Finally, the reference point approach procedure is
carried out in the normal manner and the first reference point after the closing of the switch “reference end
position” is evaluated.
3.7 “Software limit switches”
(Please note, emergency stop limit switches are still necessary on the machine!)
Via machine parameters, it is possible to program TNC 151/TNC 155 for permissible travel of the three axes,
see “Software limit switch-range setting”.
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