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

3.1.2.2

Behavior at outer corners

At outside corners during circumferential milling with 3D-TRC analogous to the conditions in the
2½D-TRC, the G commands of Group 18 (corner behavior tool offset) are evaluated:
● G450: Transition circle (tool travels around workpiece corners on a circular path)
Outside corners are treated like circles with a radius of 0, where the circular plane stretches
from the end tangent of the first block and the start tangent of the second block. Thus, an
orientation change during the block transition is also possible. Thus, a block is always
inserted at an outside corner.
In contrast to the solution for the 2½D-TRC, the contour element inserted at an outside
corner is always a circle with a radius of 0, which is affected by the tool radius compensation
like on any other programmed path. It is not possible to insert conical sections in place of the
circles. The address DISC therefore has no relevance in this case and is not evaluated.
● G451: Intersection of equidistant paths (tool backs off from the workpiece corner)
The intersection is determined by extending the offset curves of the two participating blocks
and defining the intersection of the two blocks at the corner in the plane perpendicular to the
tool orientation.
If an intersection is found in the plane perpendicular to the tool, this does not mean that the
curves also intersect in space. Rather the curves in the direction of the tool longitudinal axis
are considered, which are generally a certain distance apart. The positional offset is
eliminated over the entire block length in direction of the tool.
The way this offset is processed in tool direction at outside corners is the same as for inside
corners.
For nearly tangential transitions, the behavior for an active G450 is the same as for G451 (limit
angle can be set via MD20210 $MC_CUTCOM_CORNER_LIMIT). Conversely, if G451 is
active, a circle is also inserted (procedure as for G450) if there is no intersection or if the corner
angle exceeds a specific value (MD20230 $MC_CUTCOM_CURVE_INSERT_LIMIT).
Behavior during orientation changes
The intersection procedure (G451) is not used when at least one block containing a change to
the tool orientation was inserted between the traversing blocks in question. In this case a circle
is always inserted at the corner.
The G commands of Group 27 (too offset for orientation change at outside corners) can be used
to define whether orientation changes, which have been programmed between the two
traversing blocks that form the corner, are executed before the beginning of the inserted circle
set or at the same time.
● ORIC: Orientation changes at outside corners are superimposed on the circle block to be
inserted.
● ORID: Orientation changes are performed before the circle block.
If two or more blocks with orientation changes (e.g. A2=... B2=... C2=...) are programmed
between two traversing blocks and ORIC is active, then the circular block to be inserted is
divided between these intermediate blocks corresponding to the amount of the individual angle
changes. Further programmed intermediate blocks without traversing and orientation motions
are executed at the programmed positions.
If ORID is active, all inserted blocks (both those with and without orientation movement) are
executed at the end of the first of the two traversing blocks. The tangent in the end point of the
Tools
Function Manual, 06/2019, A5E47435126B AA
W5: 3D tool radius compensation
3.1 Function
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