Siemens SINUMERIK 840D sl Function Manual page 1441

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).
Figure 18-37 Retraction behavior with G462
The search for the intersection is then identical to the procedure for G461.
With G462, the corner generated by N10 and N20 in the sample program is not machined to
the full extent actually possible with the tool used. However, this behavior may be necessary
if the part contour (as distinct from the programmed contour), to the left of N20 in the example,
is not permitted to be violated even with y values greater than 10 mm.
If KONT is active (travel round contour at start or end point), behavior will differ according to
whether the end point is in front of or behind the contour.
End point in front of contour
If the end point is located in front of the contour, the retraction behavior is the same as for
NORM. This feature does not change, even if the last contour block with G451 is extended with
a straight line or a circle. Additional circumnavigation strategies to avoid a contour violation in
the vicinity of the contour end point are therefore not required.
End point behind contour
If the end point is behind the contour, a circle or straight line is always inserted depending on
G450/G451. In this case, G460-G462 has no effect.
If, in this situation, the last traversing block has no intersection with a preceding block, an
intersection with the inserted contour element or with the linear section from the end point of
the circumnavigation circle to the programmed end point can result.
If the inserted contour element is a circle (G450), and it intersects with the preceding block,
this is the same as the intersection, which would be produced with NORM and G461. In general,
however, a remaining section of the circle still has to be traversed. An intersection calculation
is no longer required for the linear section of the retraction block.
Basic Functions
Function Manual, 01/2015, 6FC5397-0BP40-5BA2
18.5 Tool radius compensation 2D (TRC)
W1: Tool offset
1441