HEIDENHAIN iTNC 530 (340 49x-05) Cycle programming - Manual (Page 465)

HEIDENHAIN iTNC 530 465
1
8
.4 MEA
S
URE KINEMA
TICS (Cy
c
le
451, DIN/ISO: G451; option)
Dispersion (standard deviation)
In the log, 'dispersion', a term from statistics, is used as a measure of
accuracy.
Measured dispersion (measured standard deviation) means that
68.3% of the actually measured spatial errors are within the specified
range (+/–).
Optimized dispersion (optimized standard deviation) means that
68.3% of the spatial errors to be expected after the correction of the
kinematics are within the specified range (+/–).
Measurement uncertainty of angles
The TNC always indicates measurement uncertainty in degrees per 1
µm of system uncertainty. This information is important for evaluating
the quality of the measured positioning errors, or the backlash of a
rotary axis.
The system uncertainty includes at least the repeatability of the axes
(backlash) as well as the positioning uncertainty of the linear axes
(positioning errors) and of the touch probe. Since the TNC does not
know the accuracy of the complete system, you must make a
separate evaluation.
„ Example of uncertainty of the calculated positioning errors:
„ Positioning uncertainty of each linear axis: 10 µm
„ Uncertainty of touch probe: 2 µm
„ Logged measurement uncertainty: 0.0002 °/µm
„ System uncertainty = SQRT( 3 * 10² + 2² ) = 17.4 µm
„ Measurement uncertainty = 0.0002 °/µm * 17.4 µm = 0.0034°
„ Example of uncertainty of the calculated backlash:
„ Repeatability of each linear axis: 5 µm
„ Uncertainty of touch probe: 2 µm
„ Logged measurement uncertainty: 0.0002 °/µm
„ System uncertainty = SQRT( 3 * 5² + 2² ) = 8.9 µm
„ Measurement uncertainty = 0.0002 °/µm * 8.9 µm = 0.0018°