Siemens SINUMERIK 840DE Programming Manual page 205

Note: A minimum speed can be defined via the setting datum $SC_MINFEED which is not
fallen short of and the same value can also be written directly out from the part program via
the system variable $SC_CONTPREC.
On the basis of the value of the contour error $SC_CONTPREC and the servo gain factor
(speed / following error ratio) of the path axes concerned, the control calculates the
maximum path speed at which the contour error produced by the overtravel does not exceed
the minimum value stored in the setting data.
Example
N10 X0 Y0 G0
N20 CPRECON
N30 F10000 G1 G64 X100
N40 G3 Y20 J10
N50 X0
Fundamentals
Programming Manual, 10.2004 Edition, 6FC5 298-7AB00-0BP1
5.7 Contour accuracy, CPRECON, CPRECOF
;Activate contour accuracy
;Machine contour at 10 m/min in continuous-path
mode
;Automatic feed limitation in circle block
;Feed without limitation to 10 m/min
Path Action
5-23