Influence Of The Type Of Acceleration And Of The Filters In Hsc Mode - Fagor CNC 8060 Installation Manual

13.2
13.
CNC 8060
CNC 8065
(R : 1709)
EF
·604·

Influence of the type of acceleration and of the filters in HSC mode.

HSC optimizing the chordal error (CONTERROR mode).
In this mode, the CNC modifies the geometry through intelligent algorithms for eliminating
unnecessary points and generating splines or polynomial transitions between blocks always
respecting the error limits set for this mode. This way, the contour is traveled at a variable
feedrate according to the curvature and the programmed parameters (acceleration and
feedrate) but without going beyond the set error limits.
This mode uses this type of acceleration is defined with parameter SLOPETYPE. The
following situations can occur when the type of acceleration has jerk.
• Jerk control permits pretty smooth velocity and acceleration profiles.
In this case, if there is no need to eliminate resonance frequencies, there is no need to
activate filters to make the path smoother. Since there are no filters, the part will be more
accurate because the path gores through the programmed points. The exception is on
sections where the CNC disconnects the spline because it exceeds the error limit and,
in that case, it executes a rounding polynomial that passes at a distance from the
programmed point lower than the error limit.
• Since the HSC mode tries to respect the jerk throughout the path, some irregularities may
result on the velocity profile, especially at the corners, and, consequently, affect the
quality of the surface finish.
In this case, the amount of jerk can be increased at the corners (parameter
CORNERJERK) or apply the smoothing frequency in the interpolation of the path
(parameter SMOOTHFREQ). Activating the smoothing frequency generates smoother
velocity and acceleration profiles, but increasing the execution time.
The effects of the filters set by the FILTER parameter are added to the effects of the filters
active in HSC; parameter HSCFILTFREQ for the CONTERROR mode.
HSC optimizing the feedrate (FASTmode).
It is the recommended way (mode) to work in the following circumstances.
• When feedrate is more important than accuracy.
• When the CONTERROR mode does not provide the desired results. When the error with
which the part has been generated is not significantly lower than the error demanded to
the CONTERROR, the execution is slower and the machined surfaces show ridges.
• When the dynamics of the machine does not respond in wide range of frequencies; i.e.
the machine shows resonance or a limited bandwidth.
The FAST mode provides a smoother surface finish at a more constant feedrate. From the
program, it is possible to indicate the percentage of feedrate to apply, over the maximum
that the CNC can reach depending on the setting of parameters LACC1 and LACC2.
Programming it is optional; if not defined, it assumes the percentage set in parameter
FASTFACTOR. This parameter affect directly the feedrate when going through the corners
and it must be borne in mind when reaching a compromise between the feedrate at the corner
and its finish quality.
This mode uses linear acceleration, regardless of the setting of parameter SLOPETYPE. For
best results, it is essential to set parameters LACC1 and LACC2 properly. Since there is no
jerk control, a filter is required for all the axes, inserted automatically, to make the machine
movement smoother. The frequency of this filter for all the axis is set in parameter
FASTFILTFREQ.
Using axis filters results in smoother velocity and acceleration profiles, but lower precision
at the corners depending on geometry and type of filter. The higher the linear acceleration
or the lower the range of frequencies of the machine, the lower the frequency of the filter
needed to generate a greater loss of accuracy to narrow the bandwidth of the system.
The effects of the filters set by the FILTER parameter are added to the effects of the filters
active in HSC; parameter FASTFILTFREQ for the FAST mode.
I n s ta ll a t io n ma n u a l.