HEIDENHAIN TNC 306 Technical Manual - Manual (Page 159)

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TNC 406/TNC 306 4 Gap control 4-59
4.2 Short Circuit Behavior
M36 on
The control must be able to react very quickly to a short circuit. A short circuit can occur during
normal positioning, but also during erosion.
If a short circuit occurs during erosion, i.e. when M36 is on and the gap control is active according to
the characteristic (see Chapter 4.1), the control reacts by retracting the electrode along the
programmed path. The control retracts the electrode until the short circuit is eliminated, or until 20
blocks have been retraced, or back to the NC block in which M36 was programmed. The retraction
velocity is determined by the characteristic or by the machine parameter MP2133, if a value has
been entered there.
M36 off
Marker M2623 causes a special short-circuit behavior during normal positioning (M36 off). As long
as this marker is set, the electrode retracts until the short circuit stops, then returns to the
workpiece at the programmed feed rate.
With Marker M2622, the PLC can suppress the short-circuit input X12. This may be required for a
tool change or to retreat from a eroded contour.
A short circuit is reported to the NC via X12. The NC then sets Marker M2782. The letter F is then
highlighted in the status display.
MP2133 Retraction speed during short circuit
Entry value: 0 to 500 [mm/min]
0 = Retraction speed from characteristic curve
Set Reset
M2782 Short circuit reported at Input X12 NC NC
M2622 Short circuit suppressed at Input X12 PLC PLC
M2623 Retraction if short circuit occurs and M36 is off PLC PLC
4.3 Retraction of the electrode during erosion
If the electrode should be retracted during the erosion process (M36 on), for example to inspect it,
Marker M2617 must be set (e.g. with a button). The electrode is retracted as long as the marker is
set or for up to 20 NC blocks, or back to the NC block in which M37 was last programmed. If the
marker is reset, the electrode returns along its previous path at the last programmed feed rate or, if
no feed rate was programmed, at the feed rate entered in Machine Parameter MP1090; or if Marker
M2620 is set, at the feed rate entered in MP2060. Marker M2780 is set during electrode retraction
and reapproach. Marker M2784 is also set during reapproach. Marker M2781 is set if the maximum
retraction point is reached.