13. Program Support Functions
13.18 Spline; G05.1
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(d) When a block markedly longer than other blocks exists in spline function
If the ith block length is Li in the spline interpolation mode, and it is given as "Li > Li - 1
×
8"
or "Li > Li + 1
×
8", the block will be interpreted as a linear section, and the spline mode will
be temporarily canceled. However, if the parameter "#8030 MINUTE LENGTH" is set to
"-1", the mode will not be canceled.
"Li > Li - 1
×
8" or "Li > Li + 1
×
8"
Li+1
Li-1
(2) Spline interpolation curve shape revision
Normally, once the spline function is entered, one curve connecting all points smoothly is
generated until the function is canceled. However, if the spline curve shape is to be revised,
the spline curve shape can be revised with the parameters.
(a) Chord error of block containing inflection point
When changing the CAD curve data into fine segments with the CAM, normally, the
tolerance (chord error) of the curve is approximated in segments that are approx. 10
μ
m. If
there is an inflection point in the curve, the length of the block containing the inflection
point may lengthen. (Because the tolerance is applied at both ends near the inflection
point.) If the block lengths with this block and the previous and subsequent blocks are
unbalanced, the spline curve in this block will have a large error in respect to the original
curve.
At sections where the tolerance (chord error) of the fine segment block and spline curve in
a block containing this type of inflection point, if the chord error in the corresponding
section is larger than the value set in parameter (#8027 Toler-1), the spline curve shape is
automatically revised so that the error is within the designated value.
However, if the maximum chord error of the corresponding section is more than five times
larger than the parameter "Toler-1" setting value, the spline function will be temporarily
canceled.
The curve is revised only in the corresponding block.
The revisions are carried out with the following conditions for each block in the spline
interpolation mode.
There is an inflection point in the spline curve, and the maximum error of the spline
curve and linear block is larger than parameter "Toler-1". (Distance between P3-P4
in Fig. 1)