Siemens SINUMERIK 840D sl Function Manual page 159

The advantages of the spline interpolation as compared to the linear interpolation are:
• Reduction of the number of required part program blocks for describing a curved contour.
• Soft, mechanical system-limiting curve characteristic also during transition between the
The disadvantages of the spline interpolation as compared to the linear interpolation are:
• For a spline curve no exact curve characteristic, but only a tolerance band can be
As in the case of the linear interpolation even while processing of splines so short blocks can
result, hence the path velocity must be reduced in the interpolation of these spline blocks.
This is alao the case, when the spline actually has a long, smooth curve. The "Combine
short spline blocks" function allows you to combine these spline blocks such that the
resulting block length is sufficient and does not reduce the path velocity.
Note
NC block compressor
The NC-block-compressor (COMPON, COMPCURV or COMPCAD) cannot be employed while
compressing spline blocks, since with this only linear blocks can be compressed.
Basic logic functions: Continuouspath Mode, Exact Stop, LookAhead (B1)
Function Manual, 11/2006, 6FC5397-0BP10-2BA0
part program blocks.
specified, within which the spline curve should lie.
Brief Description
7