Siemens SINUMERIK 840D sl Function Manual page 1843

Supplementary conditions
The approach and retraction blocks are polynomials in the following two variants. Therefore,
they are only available for control variants, which support polynomial interpolation.
• KONTT
• KONTC
Although KONTC includes the KONTT property, the constant tangent version KONTT is
available on its own, because the constant curvature required by KONTC can produce
undesired contours.
Axes
The continuity condition is observed in all three axes. It is thus possible to program a
simultaneous path component perpendicular to the compensation plane for
approach/retraction.
Only linear blocks are permitted for the original approach and retraction blocks with
KONTT/KONTC. These programmed linear blocks are replaced in the control by the
corresponding polynomial curves.
Exception
KONTT and KONTC are not available in 3D variants of tool radius compensation (CUT3DC,
CUT3DCC, CUT3DF).
If they are programmed, the control switches internally to NORM without an error message.
Example for KONTC
The two figures below show a typical application for approach and retraction with constant
curvature:
The full circle is approached beginning at the circle center point. The direction and curvature
radius of the approach circle at the block end point are identical to the values of the next
circle. Infeed takes place in the Z direction in both approach/retraction blocks
simultaneously.
Basic logic functions: Tool Offset (W1)
Function Manual, 11/2006, 6FC5397-0BP10-2BA0
With KONTT, approach and retraction to/from the contour is with a constant tangent. The
curvature at the block transition is not usually constant.
With KONTC, not only the tangent but also the curvature is constant at the transition, with
the result that a jump in acceleration can no longer occur on activation/deactivation.
Detailed Description
2.4 Tool radius compensation 2D (TRC)
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