Siemens SINUMERIK 840Di sl Programming Manual page 361

Deactivate compensation mode, G40, KONT
If the retraction point is located in front of the contour, the same retraction movement as for
NORM applies.
If the retraction point is located behind the contour, the retraction movement is the reverse of
the approach movement.
Precondition for KONTC and KONTT
The two functions KONTC and KONTT are available only if polynomial interpolation is
enabled in the control.
Description of KONTC and KONTT
The continuity conditions are observed in all three axes. It is therefore permissible to
program a path component perpendicular to the offset plane simultaneously.
Exception:
KONTT and KONTC are not available in the 3D variants of the tool radius compensation
(CUT3DC, CUT3DCC, CUT3DF).
If they are programmed, the control switches internally to NORM without an error message.
Difference between KONTC and KONTT
This diagram shows the differences in approach/retract behavior between KONTT and
KONTC. A circle with a radius of 20 mm about the center point at X0 Y-40 is compensated
with a tool with an external radius of 20 mm. The tool center point therefore moves along a
circular path with radius 40 mm. The end point of the approach blocks is at X40 Y30. The
transition between the circular block and the retraction block is at the zero point. Due to the
extended continuity of curvature associated with KONTC, the retraction block first executes a
movement with a negative Y component. This will often be undesired. This response does
not occur with the KONTT retraction block. However, with this block, an acceleration step
change occurs at the block transition.
Fundamentals
Programming Manual, 11/2006, 6FC5398-1BP10-2BA0
8.9 Contour approach and retraction (NORM, KONT, KONTC, KONTT)
Tool offsets
361