HEIDENHAIN TNC 640 (34059x-02) Cycle programming - Manual (Page 428)

Touch Probe Cycles: Automatic Datum Setting
16.4 DATUM FROM INSIDE OF RECTANGLE (Cycle 410, DIN/ISO: G410)
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TNC 640 | User's Manual Cycle Programming | 5/2013
Please note while programming:
Danger of collision!
To prevent a collision between touch probe and
workpiece, enter
low estimates for the lengths of
the first and second sides.
If the dimensions of the pocket and the safety
clearance do not permit pre-positioning in the
proximity of the touch points, the TNC always starts
probing from the center of the pocket. In this case
the touch probe does not return to the clearance
height between the four measuring points.
Before a cycle definition you must have programmed
a tool call to define the touch probe axis.
If you set a datum (Q303 = 0) with the touch probe
cycle and also use probe in TS axis (Q381 = 1), then
no coordinate transformation must be active.