Siemens SINUMERIK 840D sl Function Manual page 251

Figure 3-8
Note
The amount by which the contact points deviate from the programmed contour will generally be
small since the explanatory example shown in the Figure, in which the machining point
"changes" the cutter side at an inside corner (the value of the angular difference Ψ about the
tool longitudinal axis between the two contact points on the tool surface is approximately 180°)
is more likely to be the exception (see also the following Figure, on the right). The angle Ψ will
normally stay almost constant so that the distance between the contact points on the tool
surface will be relatively small (see also the following Figure, on the left).
Figure 3-9
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
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
(Page 242), 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
Tools
Function Manual, 06/2019, A5E47435126B AA
Inside corner with face milling (view in direction of longitudinal axis of tool)
Machining at inside corners
W5: 3D tool radius compensation
/ and / of the change in orientation.
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3 3
3.1 Function
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