# Definition of terms

The following terms are briefly explained:

 Polynomial contouring: Curvature and direction-continuous connection of two motion blocks. Contouring curve: Curve composed of two 4th order polynomials per axis. Block length: The path length of the curve corresponding to the motion block. Corner distance: Distance from the start/end of the contouring curve to the programmed target point/starting point of a motion block (see figure below). The corner distance is always limited to half the block length. In a circular block, the corner distance is the arc length from the starting point of the contouring curve up to the programmed target point of the arc.
 Pre-block: Motion block before the contouring curve Post-block: Motion block after the contouring curve Pre-distance: Corner distance of the pre-block Post-distance: Corner distance of the post-block Interim point: Point at which the two partial curves of the contouring curve meet. Corner deviation: The distance between the programmed corner point and the interim point of the contouring curve (see figure below).

## Programing Example

Comparing the programming of G61 – G261/G260

The 3 NC programs all generate the identical contour shown in the figure below.

 %poly_G61 N10  X0   Y0 G01 F1000 N20  X20  Y100 N30  G61  X40 Y100 N40  G61  X60 Y20 N50  G61  X80 Y20 N60  G61  X100 Y100 N70  X120 Y100 N80  X140 Y20 N90  X160 Y20 N100 M30 %poly_G261_1 N10  X0   Y0 G01 F1000 N20  X20  Y100 N30  G261 X40 Y100 N40  X60  Y20 N50  X80  Y20 N60  X100 Y100 N70  G260 X120 Y100 N80  X140 Y20 N90  X160 Y20 N100 M30 %poly_G261_2 N10 X0   Y0 G01 F1000 N20 X20  Y100 N25 G261 N30 X40  Y100 N40 X60  Y20 N50 X80  Y20 N60 X100 Y100 N70 X120 Y100 N75 G260 N80 X140 Y20