Siemens SINUMERIK 828D Function Manual page 148

B1: Continuous­path Mode, Exact Stop, LookAhead
3.1 Brief Description
Adaptation of the dynamic path response
In addition to "smoothing the path velocity", "dynamic path response adaptation" is another function for avoiding
high-frequency excitations of machine resonances while optimizing the dynamic path response at the same time.
To this end, highly frequent changes in path velocity are automatically executed with lower jerk or acceleration
values than the dynamic response limit value parameters assigned in the machine data.
Thus, with low-frequency changes in path velocity, the full dynamic response limit values apply, whereas with
high-frequency changes, only the reduced dynamic response limit values act due to the automatic dynamic
response adaptation.
Dynamic response mode for path interpolation
Optimizing the path dynamic response also includes the technology-specific dynamic response settings which
are preset for different processing technologies (including tapping, roughing, smoothing) and can be activated in
the part program by calling the respective dynamic response mode.
Free-form surface mode
Any fluctuation in curvature or torsion leads to a change in path velocity. This generally results in unnecessary
decelerating and accelerating during the processing of free-form surface workpieces, which may adversely affect
the quality of the surfaces of the workpieces.
The following functions are available for processing free-form surfaces.
• "Free-form surface mode: Basic functions"
This makes the definition of the path velocity profile "less sensitive" to fluctuations in curvature and torsion.
• "Free-form surface mode: Extension function"
This extension in standard LookAhead functionality is used to calculate the path velocity profile during the
processing of free-form surfaces.
The advantages of free-form surface mode lie in a more homogeneous workpiece surface and lower machine
load.
NC block compression
When a workpiece design is completed with a CAD/CAM system, the CAD/CAM system generally also compiles
the corresponding part program to create the workpiece surface. To do so, most CAD/CAM systems use linear
blocks to describe even curved sections of the workpiece surface. Many interpolation points are generally
necessary to maintain the required contour accuracy. This results in many linear blocks, typically with very short
paths.
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
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Function Manual, 09/2011, 6FC5397-0BP40-2BA0
Basic Functions