Siemens sinumerik 840d Programming Manual page 226

Transformations
7
7.1 Three, four and five-axes transformation: TRAORI
840D
NCU 572
NCU 573
Face milling
The face milling mode is used to machine surfaces
with any degree of curvature.
For this type of 3D milling, you require line-by-line
definition of 3D paths on the workpiece surface.
The tool shape and dimensions are taken into
account in the calculations that are normally
performed in CAM.
After they have been calculated, the NC blocks are
read into the control via postprocessors.
Definition of surfaces
The path curvature is defined via surface normal
vectors with the following components:
A4, B4, C4 Start vector at block beginning
A5, B5, C5 End vector at end of block
If a block only contains the start vector, the normal
surface vector remains constant over the entire block.
If a block only contains the end vector, then large-
circle interpolation is used to interpolate from the
end value of the preceding block to the programmed
end value.
If the start and end vectors are programmed, then
large-circle interpolation is used to interpolate
between the two directions, producing continuously
smooth traversing paths. This means it is possible to
create continuous smooth paths.
In the basic setting, the normal surface vectors point
in the Z direction, regardless of active planes G17 to
G19.
The length of a vector has no significance.
Unprogrammed vector components are set to zero.
When ORIWCS is active (see following pages), the
normal surface vectors refer to the active frame and
are rotated at the same time as the frame.
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840Di
SINUMERIK 840D/840Di/810D/FM-NC Programming Guide Advanced (PGA) − 04.00 Edition
08.97
7
A4
B4
A5
C4
B5
C5
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