Deselecting spline interpolation

Release Note


As of Build V2.11.2010.02 the command #SPLINE OFF replaces the command #SET SPLINE OFF. For compatibility reasons, this command is still available but it’s recommended not to use it in new NC programs.

#SPLINE OFF                                                                                                             (modal)

Deselecting B spline interpolation is only permitted if at least 4 vertices are programmed.

If the command is programmed in one statement together with a position, the respective point is no longer part of the B spline curve.

Alternatively, B spline interpolation can be deselected using the G150 command.

Programing Example


Deselecting spline interpolation


N20  G01 X0 Y50 Z0 F10000


N40   X3     Y25

N50   X15    Y15

N60   X23    Y12

N70   X25    Y25

N80   X30    Y35

N90   X50    Y37.5

N100  X55    Y32.5

N110  X58    Y12

N120  X70    Y12

N130  X77.5  Y10

N140  X90    Y35

N150  X100   Y37.5


N170 M30

The figure below shows the contour resulting from the programming example:

Contour resulting from programming example
Contour resulting from programming example

The figure shows the smoothing property of a B spline curve, especially for blocks N120/N130. Moreover, it shows that the curve does not pass through the control points. However, the polygon resulting from connecting the control points provides an estimation of the actual shape of the B spline curve.



With a B spline curve, it is not possible to specify the tangents at curve ends directly. However, because the tangents of the B spline curve has the same tangents of corresponding motion blocks at the curve end, the tangents may be specified by programming the first and last motion blocks.