HEIDENHAIN TNC 426B (280 472) Touch Probe Cycles - Manual (Page 60)

48 3 Touch Probe Cycles for Automatic Workpiece Inspection
3.2 A
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ting
DATUM FROM INSIDE OF CIRCLE (touch probe
cycle 412, ISO: G412)
Touch probe cycle 412 finds the center of a circular pocket (or of a
hole) and defines its center as datum. If desired, the TNC can also
enter the coordinates into a datum table.
1 The TNC positions the touch probe to the starting points at rapid
traverse (value from MP6150 or MP6361) following the positioning
logic (see “Running touch probe cycles” on page 7) to the starting
point
1 . The TNC calculates the probe starting points from the data
in the cycle and the safety clearance from MP6140.
2 Then the touch probe moves to the entered measuring height and
probes the first touch point at the probing feed rate (MP6120 or
MP6360). The TNC derives the probing direction automatically
from the programmed starting angle.
3 Then the touch probe moves in a circular arc either at measuring
height or at clearance height to the next starting point
2 and probes
the second touch point.
4 The TNC positions the probe to starting point 3 and then to starting
point 4 to probe the third and fourth touch points.
5 Finally the TNC returns the touch probe to the clearance height and
sets the datum at the measured center, or enters its coordinates
in the active datum table.
2
1
4
3
Before programming, note the following:
To prevent a collision between the touch probe and the
workpiece, enter a low estimate for the nominal diameter
of the pocket (or hole).
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.