Siemens SINUMERIK 840Di sl Programming Manual page 360

Tool offsets
8.9 Contour approach and retraction (NORM, KONT, KONTC, KONTT)
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.
360
G450
G450
G451
G451
Programming Manual, 11/2006, 6FC5398-1BP10-2BA0
Fundamentals