Dynamic Adaptations; Smoothing The Path Velocity - Siemens SINUMERIK 828D Function Manual

B1: Continuous­path Mode, Exact Stop, LookAhead

3.4 Dynamic adaptations

3.4 Dynamic adaptations
3.4.1

Smoothing the path velocity

Introduction
The velocity control function utilizes the specified axial dynamic response. If the programmed feedrate cannot be
achieved, the path velocity is brought to the parameterized axial limit values and the limit values of the path
(velocity, acceleration, jerk). This can lead to repeated braking and acceleration on the path.
If a short acceleration takes place during a machining function with high path velocity, and is thus followed almost
immediately by braking, the reduction in the machining time is only minimal. Acceleration of this kind can,
however, have undesirable effects if, for example, it results in machine resonance.
In some applications in mold making, especially in the case of high speed cutting, it is desirable to achieve a
constant path velocity. In these cases, it can therefore be reasonable to sacrifice transient acceleration
processes in favor of a smoother tool path velocity.
Function
If the "smoothing the path velocity" function is active, a smoothing factor, which determines the maximum
permissible productivity loss, takes effect with a view to achieving smoother path velocity control: Acceleration
processes which contribute less than this factor to a shorter program runtime are not performed. Account is only
taken of acceleration processes whose frequencies lie above the configurable limit frequencies of of the axes
involved.
Benefits:
• Avoidance of excitations of possible machine resonance due to continuous, transient braking and
acceleration processes (in the area of less IPO cycles).
• Avoiding of constantly varying cutting rates due to acceleration which brings no significant shortening of the
program running time.
Note
The smoothing of the path velocity does not lead to contour errors.
Variations in axis velocity due to curvatures in the contour at constant path velocity may
continue to occur and are not reduced with this function.
Variations in path velocity due to the input of a new feedrate are not changed either. This
remains the responsibility of the programmer of the subprogram.
Requirements
• The smoothing of the path velocity is only effective in continuous-path mode with LookAhead over multiple
blocks with SOFT and BRISK. Smoothing is not effective with G0.
• The controller's cycle times must be configured in such a way that preprocessing can prepare sufficient blocks
to enable an acceleration process to be analyzed.
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Function Manual, 09/2011, 6FC5397-0BP40-2BA0
Basic Functions