Siemens sinumerik 840D sl Function Manual page 873

Detailed description
2.2 Face milling
The difference between the programmed point on the path and the point actually to be
approached (path offset p) is eliminated linearly over the entire block length. Differences
resulting from inside corners at the block start and block end are overlaid. The current
difference in a path point is always perpendicular to the path and in the surface defined by
the surface normal vector.
If the tool orientation at an inside corner is not constant, the change in orientation is
implemented in the same way as described in Subsection "Behavior at inside corners" for 3D
circumferential milling, i.e. the tool is moved in the corner so that it contacts the two adjacent
surfaces at the block start, block end and at two points
orientation. A 3rd-degree polynomial is used to interpolate between these 4 points.
A variable tool orientation in a block that is shortened owing to an inside corner is also
treated in the same way as described in Subsection "Behavior at inside corners" for 3D
milling, i.e. the entire change in orientation is executed in the shortened block. Consequently,
the functional relationship between path tangent, surface normal and tool orientation also
changes. This results in new, previously nonexistent singularities or impermissible side
angles (at points which are virtually singular) occurring in the shortened block. If this type of
situation is detected during processing of an inside corner, the machining operation is
aborted with an alarm. No block division takes place at the singular points since the
compensatory motions this would involve frequently cause contour violations and the change
in machining side on the tool is not generally intended or even foreseen by the user. The
alarm is also output during examination of an inside corner if the singularity occurs in the
second of the two blocks without the transition to the next block being considered. The
system does not therefore detect that a block of this type will form an inside corner in
conjunction with the following block and that the singularity would be eliminated again by the
second block reduction.
The surface normal vector n
contrast to the tool orientation, the change in orientation that may need to be executed for
this vector will not be imaged onto the reduced traversing interval. This is necessary
because a surface other than that programmed would be machined. Unlike the tool
orientation, no problems arise as the result of an abrupt change in the surface normal vector
at a block transition since it does not reflect any axis motions.
Analogously to 3D circumferential milling, (see Subsection "Behavior at inside corners"), the
two traversing blocks that form an inside corner must contain contact points. There is no
evaluation of several traversing blocks (i.e. no bottleneck detection), CDON/CDOF are not
evaluated. If no contact point can be found, the machining operation is aborted with an alarm
(risk of collision).
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is not affected by the reduction of a block. This means that in
F
Special functions: 3D Tool Radius Compensation (W5)
/ and / of the change in
1 2
3 3
Function Manual, 11/2006, 6FC5397-2BP10-2BA0