HEIDENHAIN TNC 640 (34059x-02) ISO programming - Manual (Page 485)

Datum Setting with 3-D Touch Probe 15.9
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TNC 640 | User's Manual for DIN/ISO Programming | 5/2013
485
Circle center as datum
With this function, you can set the datum at the center of bore
holes, circular pockets, cylinders, studs, circular islands, etc.
Inside circle:
The TNC probes the inside wall of a circle in all four coordinate axis
directions.
For incomplete circles (circular arcs) you can choose the
appropriate probing direction.
Position the touch probe approximately in the center of the
circle
Select the touch probe function: Press the
PROBING CC soft key
Select the probing direction or press the soft key
for the automatic probing routine
To probe the workpiece, press the machine START
button. The touch probe probes the inside wall
of the circle in the selected direction. If you are
not using the automatic probing routine, you need
to repeat this procedure. After the third probing
operation, you can have the TNC calculate the
center (four touch points are recommended).
Terminate the probing procedure and switch to the
evaluation menu: Press the EVALUATE soft key
Datum: In the menu window, enter both
coordinates of the circle center, confirm with the
SET DATUM soft key, or write the values to a table
(See "Writing measured values from the touch
probe cycles in a datum table", page 472, or See
"Writing measured values from the touch probe
cycles in the preset table", page 473)
Terminate the probing function: Press the END
soft key
The TNC needs only three touch points to calculate
outside or inside circles, e.g. for circle segments.
More precise results are obtained if you measure
circles using four touch points, however. You should
always preposition the touch probe in the center, or
as close to the center as possible.