Siemens SINUMERIK 840D sl Programming Manual page 311

Further information
G461
If no intersection is possible between the last TRC block and a preceding block, the offset
curve of this block is extended with a circle whose center point lies at the end point of the
uncorrected block and whose radius is equal to the tool radius.
The control attempts to cut this circle with one of the preceding blocks.
Figure 10-4
Collision monitoring CDON, CDOF
If CDOF is active (see section Collision monitoring, CDON, CDOF), the search is aborted
when an intersection is found, i.e., the system does not check whether further intersections
with previous blocks exist.
If CDON is active, the search continues for further intersections after the first intersection is
found.
An intersection point, which is found in this way, is the new end point of a preceding block and
the start point of the deactivation block. The inserted circle is used exclusively to calculate the
intersection and does not produce a traversing movement.
Note
If no intersection is found, alarm 10751 (collision danger) is output.
G462
If no intersection is possible between the last TRC block and a preceding block, a straight line
is inserted, on retraction with G462 (initial setting), at the end point of the last block with tool
radius compensation (the block is extended by its end tangent).
The search for the intersection is then identical to the procedure for G461.
Retraction behavior with G462 (see example)
Fundamentals
Programming Manual, 09/2011, 6FC5398-1BP40-2BA0
Retraction behavior with G461
Tool radius compensation
10.4 Smooth approach and retraction
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