Siemens SINUMERIK 840Di Function Manual page 1759

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.
In the second case (if no intersection is found between the inserted contour element and the
preceding blocks), the intersection between the retraction straight line and a preceding block
is approached.
Therefore, when G461 or G462 is active, behavior deviating from G460 can only arise if
NORM is active or if behavior with KONT is identical to NORM due to the geometrical conditions.
Note
The approach behavior is symmetrical to the retraction behavior.
The approach/retraction behavior is determined by the state of the G command in the
approach/retraction block. The approach behavior can therefore be set independently of the
retraction behavior.
Example:
Program for using G461 during approach:
N10 $TC_DP1[1,1]=120
N20 $TC_DP6[1,1]=10
N30 X0 Y0 F10000 T1 D1
N40 Y20
N50 G42 X50 Y5 G461
N60 Y0 F600
N70 X30
N80 X20 Y-5
N90 X0 Y0 G40
N100 M30
Tool Compensation (W1)
Function Manual, 08/2005 Edition, 6FC5397-0BP10-0BA0
2.4 Tool: Tool radius compensation 2D (TRC)
; Tool type mill
; Radius
Detailed Description
2-79