Compensation On Path - Siemens SINUMERIK 840D sl Function Manual

W5: 3D tool radius compensation
3.1 Function
from their programmed values at the path end point. This is because the orientation has
changed relative to the surface normal vector or path tangent vector when the absolute
orientation of the tool is the same as at the original path end point.
3.1.3.3

Compensation on path

A special case must be examined with respect to face milling operations, i.e. that the machining
point on the tool surface moves around. This may be the case on a torus cutter whenever
surface normal vector n
to the surface) since it is not a single point on the tool that corresponds to this direction, but the
entire circular surface on the tool end face. The contact point is therefore not defined for this
orientation. A path point in which tool longitudinal axis and surface normal are parallel is
therefore referred to below as a singular point or a singularity.
The above case is also meaningful in practical terms, e.g. in cases where a convex surface,
which may have a vertical surface normal (e.g. hemisphere), must be machined with a
perpendicular tool (e.g. face milling with constant orientation). The machining point on the
contour remains fixed, but the machine must be moved to bring the machining point from one
side of the tool to the other.
The problem described is only a borderline case (lead angle β = 0 and side angle y = 0). If the
lead angle β = 0 and the side angle y has a low value, then the tool must be moved very rapidly
(in borderline case in steps) to keep the machining point resulting from the milling conditions
close to the arc-line forming the end face (see the following figure).
In principle, it is resolved by the smoothing of the surface normal and the smoothing of the
contour.
Figure 3-6
Singularities do not only occur in isolated points, but can also occur over entire curves. This is
the case, for example, if the curve to be interpolated is a plane curve (i.e. a curve with a constant
osculating plane) and the tool is constantly aligned in parallel to the binormal vector
(perpendicular to the osculating plane). A simple example of this is an arc in the X-Y plane,
which is processed with a tool that is aligned parallel to the Z axis. For paths of this type, the tool
offset is reduced to a tool length compensation. I.e. the tool is positioned in such a way that its
tip lies on the programmed path.
For a jump-like transition between singular and non-singular curves, linear blocks must be
inserted, just as in the handling of individual points, so that the processing point on the tool can
248
and tool vector w become collinear (i.e. the tool is at exact right angles
F
Switching of the processing point on the tool surface in the vicinity of a point in which the
surface normal vector and the tool orientation are parallel.
Function Manual, 06/2019, A5E47435126B AA
Tools