HEIDENHAIN ND 1300 OED and Crosshair Systems - Manual (Page 199)

NLEC Screen
The NLEC screen contains fields for enabling and
configuring nonlinear error correction (NLEC) for
the X and Y encoder axes.
Nonlinear error correction minimizes or eliminates
the small inaccuracies in the X-Y measurement
plane due to encoder linearity, mounting and ma-
chine-travel imperfections. Error correction coef-
ficients are obtained by measuring a certified cali-
bration grid. When the grid is measured, values are
compared to either the ideal grid values as described
by the Grid Size and Cell Size fields, or to the certified grid values listed in an artifact calibration file (.acf
file). This comparison of measured values to ideal or actual values results in the final NLEC.txt file that
contains the error corrections for all measured grid locations. When NLEC is enabled, the corrections will
applied across the entire range of X-Y measurement to minimize or eliminate the inaccuracies mentioned
earlier.
.acf Files
When no .acf file is used, the calibration grid values are assumed to be ideal. When grid certification values
are available, an .acf file can be created easily using a word processor application. The format of the .acf
file is shown here with an example 3 X 3 grid and corresponding example .acf file. Create a text file of
actual grid values from the certification sheet and save the file using the nlec.acf file name and extension.
.acf file format
Unit of measure Skew axis
Size of Y cells Size of X cells
Number of X points Number of Y points
First X grid value First Y grid value
Next X grid value First Y grid value
Next X grid value First Y grid value
. .
. .
. .
Next X grid value Last Y grid value
Last X grid value Last Y grid value
Example .acf file
mm X
25.4 25.4
3 3
0.0000 0.0000
25.4003 0.0001
50.7998 0.0003
-0.0002 24.3997
25.4001 25.4004
50.8003 24.3999
0.0001 50.8001
25.4004 50.8004
Example 3 X 3 grid
NLEC Screen 181
10
Setup