Siemens SINUMERIK 828D Function Manual page 149

Combine short spline blocks
A spline defines a curve which is formed from 2nd or 3rd degree polynomials. With spline interpolation, the
controller can generate a smooth curve characteristic from only a few specified interpolation points of a set
contour.
References:
Programming Manual, Advanced, Special motion commands,
chapter: Spline interpolation
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 part program blocks.
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 specified, within which the
spline curve should lie.
As with linear interpolation, the processing of splines can produce such short blocks that the path velocity must
be reduced to enable interpolation of the 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 it can only be used to compress linear blocks.
Basic Functions
Function Manual, 09/2011, 6FC5397-0BP40-2BA0
B1: Continuous­path Mode, Exact Stop, LookAhead
3.1 Brief Description
149