Behavior At Inside Corners - Siemens SINUMERIK 840D sl Function Manual

W5: 3D tool radius compensation
19.3 Face milling
19.3.6

Behavior at inside corners

The position of the tool in which it is in contact with the two surfaces forming the corner must
be determined at an inside corner. The contact points must be on the paths defined on both
surfaces. It is not usually possible to solve this problem exactly since, when the tool is moved
along the path on the first surface, it normally touches a point on the second surface which is
not on the path.
For this reason, the tool is not moved along the path on the first surface, but deviates from the
path in such a way as to ensure that the distance between the contact points and the relevant
contours in the position in which the tool contacts both surfaces is minimal, see also the
following Figure.
Figure 19-17 Inside corner with face milling (view in direction of longitudinal axis of tool)
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 19-18 Machining at inside corners
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.
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Function Manual, 09/2011, 6FC5397-2BP40-2BA0
Special Functions