Contour Accuracy, Cprecon, Cprecof - Siemens SINUMERIK 840D sl Programming Manual

Supplementary commands

14.9 Contour accuracy, CPRECON, CPRECOF

14.9 Contour accuracy, CPRECON, CPRECOF
Function
In machining operations without feedforward control (FFWON), errors may occur on curved
contours as a result of velocity-related differences between setpoint and actual positions.
The programmable contour accuracy function CPRECON makes it possible to store a
maximum permissible contour violation in the NC program which must never be overshot.
The magnitude of the contour violation is specified with setting data $SC_CONTPREC.
The Look Ahead function allows the entire path to be traversed with the programmed contour
accuracy.
Syntax
CPRECON
CPRECOF
Significance
CPRECON:
CPRECOF:
Note
A minimum velocity can be defined via the setting data item $SC_MINFEED, which is not
undershot, 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 violation $SC_CONTPREC and the servo gain factor
(velocity/following error ratio) of the geometry axes concerned, the control calculates the
maximum path velocity at which the contour violation produced by the overtravel does not
exceed the minimum value stored in the setting data.
Example
Program code
N10 X0 Y0 G0
N20 CPRECON
N30 F10000 G1 G64 X100
N40 G3 Y20 J10
N50 X0
414
Activate programmable contour accuracy
Deactivate programmable contour accuracy
Comment
; Activate contour accuracy
; Machining at 10 m/min in continuous-path mode
; Automatic feed limitation in circular block
; Feedrate without limitation 10 m/min
Programming Manual, 09/2011, 6FC5398-1BP40-2BA0
Fundamentals