Siemens SINUMERIK 840D sl Function Manual page 178

B1: Continuous-path mode, Exact stop, Look Ahead
4.1 Brief Description
This results in the following advantages:
● Improved surface quality and machining time by avoiding excitation of machine resonances.
● Constant profile of path velocity and cutting rates by avoiding "unnecessary" acceleration
processes, i.e. acceleration processes that do not greatly improve the program run time.
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.
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Function Manual, 01/2015, 6FC5397-0BP40-5BA2
Basic Functions