Siemens SINUMERIK 840D sl Function Manual page 179

The "NC block compressor" function uses polynomial blocks to perform a subsequent
approximation of the contour specified by the linear blocks. During this process, an assignable
number of linear blocks is replaced by a polynomial block. Furthermore, the number of linear
blocks that can be replaced by a polynomial block also depends on the specified maximum
permissible contour deviation and the contour profile.
Use of polynomial blocks provides the following advantages:
● Reduction of the number of required part program blocks for describing the workpiece
contour
● Higher maximum path velocities
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, 01/2015, 6FC5397-0BP40-5BA2
B1: Continuous-path mode, Exact stop, Look Ahead
4.1 Brief Description
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