Smoothing methods


A programmed curve must be rounded and smoothed within specific tolerances to allow it to move even over corners without stopping as quickly and uniformly as possible. This is referred to as smoothing and there are various methods provided.

Simple contours with few long linear and circular blocks are ideal for polynomial contouring. Select this function with G261 and deselect with G260. This method is described in Section G functions.

On the other hand, it is preferable to use #HSC methods when there are many short linear blocks. The methods include the highly rugged SURFACE method that is particularly suited to free-form surface machining. It achieves the best results in the event of disruptions in the programmed contour and blocks which have very different lengths. By contrast, this places greater requirements on the hardware. The B spline method can also be used to trim a contour.. It requires less high-performance hardware but may lead to drops in path velocity on less properly programmed contours.

If these HSC programs also contain circular blocks, the transitions can be smoothed by #CONTOUR MODE functions. This requires the option CIR_MODE and the channel parameter P-CHAN-00239 which are described in the sections mentioned above. HSC programs may also include circular blocks. If NC programs contains many short blocks, it is advisable to use the HSC profile generator #SLOPE[TYPE=HSC].

Besides smoothing a programmed contour, a frequent function is to filter axis command values symmetrically. These functions are described in Section Filter programming.

Besides these recommended standard methods, there are a number of other methods such as interpolation with the Akima spline, the direct programming of B spline control points and older HSC functions.

Name of function

Its suitability




For simple contours with few long blocks

Greater path velocities at contour knee angles

Not for short blocks

SURFACE methods

For complex contours with several short blocks

Very rugged

Increased hardware requirements

B spline method

Trim a contour

Slow motion sections with unfavourable programming

Not so high hardware requirements

Filter programming

To filter axis command values symmetrically



Akima spline

Interpolate specified interpolation points

Runs precisely through the programmed points

Generally requires a denser and exactly calculated specification of points

PSC functions with OP1 and OP2

Rigid machines

Low hardware requirements

Relatively strong excitation of machine structure