Siemens SINUMERIK 840DE Programming Manual page 343

Selecting the approach and retraction direction
Use the tool radius compensation (G140, basic setting) to determine the approach and
retraction direction with positive tool radius:
• G41 active → approach from left
• G42 active → approach from right
G141, G142 and G143 provide further approach options.
Description
The G codes are only significant when the approach contour is a quadrant or a semicircle.
Fundamentals
Programming Manual, 10.2004 Edition, 6FC5 298-7AB00-0BP1
8.11 Smooth approach and retraction
Tool offsets
8-47