Siemens SINUMERIK 840D sl Programming Manual page 275

Figure 2-16
Selecting the approach and retraction direction
Use the tool radius compensation (G140, default 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.
The G codes are only significant when the approach contour is a quadrant or a semicircle.
NC programming
Programming Manual, 12/2019, 6FC5398-2EP40-0BA0
Approach movements with simultaneous activation of the tool radius compensation
Fundamentals
2.10 Tool radius compensation
275