Siemens SINUMERIK 840D sl Programming Manual page 291

Approach/Retraction with KONT
Prior to the approach the tool can be located in front of or behind the contour. The path
tangent at the starting point serves as a separation line:
Accordingly, two scenarios need to be distinguished where approach/retraction with KONT is
concerned:
1. The tool is located in front of the contour.
→ The approach/retract strategy is the same as with NORM.
2. The tool is located behind the contour.
-
Fundamentals
Programming Manual, 09/2011, 6FC5398-1BP40-2BA0
10.2 Contour approach and retraction (NORM, KONT, KONTC, KONTT)
Approach:
The tool travels around the starting point either along a circular path or over the
intersection of the equidistant paths depending on the programmed corner behavior
(G450/G451).
The commands G450/G451 apply to the transition from the current block to the next
block:
Tool radius compensation
291