HEIDENHAIN TNC 640, User Manual, Page: 491 / 948

Miscellaneous Functions | Miscellaneous functions for path behavior
11
HEIDENHAIN | TNC 640 | Conversational Programming User's Manual | 10/2017
491
Calculating the radius-compensated path in advance
(LOOK AHEAD): M120
Standard behavior
If the tool radius is larger than the contour step that needs to
be machined with radius compensation, the control interrupts
program run and generates an error message.
M97
inhibits the
error message, but this results in dwell marks and will also move
the corner.
Further information: "Machining small contour steps: M97",
page 486
The control might damage the contour in case of undercuts.
Behavior with M120
The control checks radius-compensated contours for undercuts and
tool path intersections, and calculates the tool path in advance from
the current block. Areas of the contour that would be damaged
by the tool will not be machined (shown darker in the figure). You
can also use
M120
to calculate the tool 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.
The number of blocks (99 max.) calculated in advance, can be
defined with
LA
( L ook A head) following
M120
. 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 control continues the
dialog for this block by prompting you for the number of
LA
blocks
to be calculated in advance.
Effect
M120
must be included in an NC block that also contains an
RL
or
RR
radius compensation.
M120
is then effective from this block
until
radius compensation is canceled with
R0
M120 LA0
is programmed
M120
is programmed without
LA
another program is called with
PGM CALL
the working plane is tilted with Cycle
19
or with the
PLANE
function
M120
becomes effective at the start of the block.