Orientation - Siemens sinumerik 840D sl Function Manual

Detailed description
2.2 Face milling
A change in tool involving only a change in other tool data (e.g. tool length) is permitted
provided that no other restrictions apply. An alarm is output if a tool is changed illegally.
2.2.2

Orientation

The options for programming the orientation have been extended for 3D face milling.
The tool offset for face milling cannot be calculated simply by specifying the path (e.g. a line
in space). The surface to be machined must also be known. The control is supplied with the
information it requires about this surface by the surface normal vector.
The surface normal vector at the block beginning is programmed with A4, B4, C4, and
the vector at the block end with A5, B5, C5. Components of the surface normal vector that
are not programmed are set to zero. The length of a vector programmed in this way is
irrelevant. A vector of zero length (all three components are zero) is ignored, i.e. the direction
programmed beforehand remains valid, no alarm is generated.
If only the start vector is programmed (A4, B4, C4) in a block, then the programmed
surface normal vector remains constant over the entire block. If only the end vector is
programmed (A5, B5, C5), then large-circle interpolation is used to interpolate between
the end value of the preceding block and the programmed end value. If both the start and
end vectors are programmed, then interpolation takes place between both directions using
the large-circle interpolation method. The fact that the start vector may be reprogrammed in
a block means that the direction of the surface normal vector can change irregularly on a
block transition. Irregular transitions of the surface normal vector always occur in cases
where there is no tangential transition between the surfaces (planes) involved, i.e. if they
form an edge.
Once a surface normal vector has been programmed, it remains valid until another vector is
programmed. In the basic setting, the surface normal vector is set to the same values as the
vector in the z direction. This basic setting direction is independent of the active plane (G17 -
G19). If ORIWKS is active, surface normal vectors refer to the active frame, i.e. when the
frame is rotated, the vectors rotate simultaneously. This applies both to programmed
orientations as well as to those derived from the active plane. If ORIWKS is active, the
surface normal vectors are adjusted when a new frame becomes active. An orientation
modified as the result of frame rotations is not returned to its original state on switchover
from ORIWKS to ORIMKS.
It must be noted that the programmed surface normal vectors may not necessarily be the
same as those used internally. This always applies when the programmed surface normal
vector is not perpendicular to the path tangent. A new surface normal vector is then
generated which is positioned in the plane extending from the path tangent to the
programmed surface normal vector, but which is at right angles to the path tangent vector.
This orthogonalization is necessary because the path tangent vector and surface normal
vector for a real surface must always be perpendicular to one another. However, since the
two values can be programmed independently, they may contain mutually contradictory
information. Orthogonalization ensures that the information contained in the path tangent
vector has priority over the data in the surface normal vector. An alarm is output if the angle
between the path tangent vector and the programmed surface normal vector is smaller than
the limit value programmed in machine data:
MD21084 $MC_CUTCOM_PLANE_PATH_LIMIT (minimum angle between surface normal
vector and path tangent vector)
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Special functions: 3D Tool Radius Compensation (W5)
Function Manual, 11/2006, 6FC5397-2BP10-2BA0