Siemens SINUMERIK 840DE Programming Manual page 333

Generation of the approach path
In both cases (G450/G451), the following approach path is generated:
A straight line is drawn from the uncompensated approach point. This line is a tangent to a
circle with circle radius = tool radius. The center point of the circle is on the starting point.
Deactivate compensation mode, G40, KONT
If the retraction point is located in front of the contour, the same retraction movement as for
NORM applies.
If the retraction point is located behind the contour, the retraction movement is the reverse of
the approach movement.
Precondition for KONTC and KONTT
The two functions KONTC and KONTT are available only if polynomial interpolation is
enabled in the control.
Fundamentals
Programming Manual, 10.2004 Edition, 6FC5 298-7AB00-0BP1
8.9 Contour approach and retraction (NORM, KONT, KONTC, KONTT)
G450
G450
G451
G451
Tool offsets
8-37