Siemens SINUMERIK 840Di sl Programming Manual page 366

Tool offsets
8.10 Compensation at the outside corners (G450, G451)
Path action, depending on DISC values and contour angle
Depending on the angle of the contour that is traversed, with acute contour angles and high
DISC values the tool is lifted off the contour at the corners. With angles of 120° and more,
the contour is traversed evenly (see adjacent table).
Corner behavior, intersection, G41, G42, G451
The tool approaches the intersection of the two equidistants, which lie in the distance
between the tool radius and the programmed contour. G451 applies only to circles and
straight lines.
At intermediate point P*, the control executes instructions such as infeed movements or
switching functions. These instructions are programmed in blocks inserted between the two
blocks forming the corner.
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Programming Manual, 11/2006, 6FC5398-1BP10-2BA0
Fundamentals