Siemens sinumerik 808d Programming And Operating Manual page 78

Programming principles
1.6 Tool and tool offset
Starting the compensation
The tool approaches the contour on a straight line and positions itself vertically to the path
tangent in the starting point of the contour.
Select the start point so as to ensure collision-free traversing.
Figure 1-44 Start of the tool radius compensation with the example G42, tool point direction
=3
The tool tip goes around the left of the workpiece when the tool runs clockwise using G41;
The tool tip goes around the right of the workpiece when the tool runs counter-clockwise
using G42.
Information
As a rule, the block with G41/G42 is followed by the block with the workpiece contour.
However, the contour description may be interrupted by an intervening block that does not
contain information for the contour path, e.g. only M command.
Programming example
N10 T4 D1 M3 S1000 F0.15
N20 G0 X0 Z0
N30 G1 G42 X50 Z50
N40 X0 Z0 G40 G1
N50 M30
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; P0 - starting point
; Selection right of contour, P1
; Starting contour, circle or straight line
Turning Part 2: Programming (Siemens instructions)
Programming and Operating Manual, 05/2012, 6FC5398-5DP10-0BA0