HEIDENHAIN ND 1200 - Manual (Page 106)

106 2 Installation and Specifications
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p Nonlinear error correction (NLEC)
NLEC minimizes or eliminates the small inaccuracies in the X-Y
measurement plane due to machine irregularities and encoder
nonlinearity. Error correction coefficients are obtained by measuring a
certified calibration grid. The actual values are then compared to the
nominal grid values by the ND 1200. This comparison results in a final
NLEC.txt file that contains the error corrections for all measured grid
locations. When NLEC is enabled, the corrections are applied across
the measured area of the X-Y measurement plane. To apply NLEC to
a measurement plane:
U Verify that the crosshair probe is selected. Press the PROBE soft
key to select it if necessary.
U Verify that the appropriate encoder reference marks are selected in
the Encoders setup screen (See "Encoders screen" on page 92).
U Verify that the Startup zero field of the Measure setup screen is set
to YES (See "Measure screen" on page 112).
U Cycle the ND 1200 power off and then back on the establish the
machine zero if necessary.
U Press MENU/SETUP to display the setup menu and then highlight
the Scale Factor menu item.
U Verify that the Active choice field specifies NO.
U Press MENU/CLEAR/CLR ALL to clear all existing datums, part
alignments and part data.
U Press MENU/SETUP to display the setup menu and then highlight
the LEC menu item.
U Verify that all Standard and Observed data fields contain the value:
1.000 to eliminate the possibility that a previous LEC correction will
influence this NLEC correction.
Reference marks, or a manual reference position must be
recognized by the ND 1200 upon startup to create a
repeatable machine zero. Machine zero is required for
NLEC error correction.
When scale factors are used, they must be applied after
error corrections.