HEIDENHAIN TNC 620 (73498x-01) ISO programming - Manual (Page 288)

288 Programming: Miscellaneous functions
9.4 Miscellaneous functions f
o
r cont
our
ing beha
vior
Calculating the radius-compensated path in
advance (LOOK AHEAD): M120
Standard behavior
If the tool radius is larger than the contour step that is to be machined
with radius compensation, the TNC interrupts program run and
generates an error message. M97 (see "Machining small contour
steps: M97" on page 283) inhibits the error message, but this results
in dwell marks and will also move the corner.
If the programmed contour contains undercut features, the tool may
damage the contour.
Behavior with M120
The TNC checks radius-compensated paths for contour undercuts and
tool path intersections, and calculates the tool path in advance from
the current block. Areas of the contour that might be damaged by the
tool are not machined (dark areas in figure). You can also use M120 to
calculate the radius compensation for digitized data or data created on
an external programming system. This means that deviations from the
theoretical tool radius can be compensated.
Use LA (Look Ahead) after M120 to define the number of blocks
(maximum: 99) that you want the TNC to calculate in advance. Note
that the larger the number of blocks you choose, the higher the block
processing time will be.
Input
If you enter M120 in a positioning block, the TNC continues the dialog
for this block by asking you the number of blocks LA that are to be
calculated in advance.
X
Y