Siemens SINUMERIK 840D sl Programming Manual page 482

Tool offsets
7.5 Activate 3D tool offsets (CUT3DC..., CUT3DF...)
Further information
Intersection procedure for 3D compensation
With 3D circumferential milling, G code G450/G451 is now evaluated i.e. the point of
intersection of the offset curves can be approached. Up to SW 4 a circle was always inserted
at the outside corners. The intersection procedure is especially advantageous for 3D
programs typically generated by CAD. These often consist of short straight blocks (to
approximate smooth curves), where the transitions between adjacent blocks are almost
tangential.
Up to now, with tool radius compensation on the outside of the contour, circles were
generally inserted to circumnavigate the outside corners. These blocks can be very short
with almost tangential transitions, resulting in undesired drops in velocity.
In these cases, analog to the 2 ½ D radius compensation, the two curves involved are
extended; the intersection of both extended curves is approached.
The intersection is determined by extending the offset curves of the two participating blocks
and defining the intersection of the two blocks at the corner in the plane perpendicular to the
tool orientation. If there is not such intersection, the corner is handled as before – i.e. a circle
is inserted.
For more information on the intersection procedure, see:
References:
Function Manual, Special Functions; 3D Tool Radius Compensation (W5)
482
Programming Manual, 06/2009, 6FC5398-2BP20-0BA0
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