Compensation On Path - Siemens SINUMERIK 840D sl Function Manual

W5: 3D tool radius compensation - 840D sl only
23.3 Face milling
would be with other interpolation quantities such as, for example, the position of an additional
synchronized axis.
In addition to the usual methods of programming orientation, it is also possible to refer the tool
orientation to the surface normal vector and path tangent vector using the addresses LEAD
(lead or camber angle) and TILT (side angle). The lead angle is the angle between the tool
orientation and the surface normal vector. The side angle is the angle between the path tangent
and the projection of the tool vector into the surface to be machined. Specification of the angle
relative to the surface normal is merely an additional option for programming tool orientation
at the block end. It does not imply that the lead and side angles reach their programmed values
before the path end point is reached.
The final tool orientation is calculated from the path tangent, surface normal vector, lead angle
and side angle at the block end. This orientation is always implemented by the end of the block,
particularly in cases where the block is shortened (at an inside corner). If the omitted path
section is not a straight line in a plane, the lead and side angles generally deviate 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.
23.3.3

Compensation on path

Tool longitudinal axis parallel to surface normal
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 not, therefore, defined with
this type of 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.
788
and tool vector w become collinear (i.e. the tool is at exact right angles
F
Function Manual, 01/2015, 6FC5397-2BP40-5BA2
Special functions