Rockwell Automation 8520-MUM 9/Series CNC Mill Operation and Programming Manual Documentation Set - Manual (Page 521)

Cutter Diameter Compensation
(G40, G41, G42)
Chapter 21
21-3
Figure 21.2
Definition of Inside and Outside
workpiece
Inside angle (less than 180 degrees)
Outside angle (greater than 180 degrees)
workpiece
Use these G-codes for cutter compensation:
G41 -- cutter compensation, left
G42 -- cutter compensation, right
G40 -- cutter compensation, cancel
Left or right is defined as offsetting the tool to the left or right of the
programmed cutting path when facing the direction of cutter motion.
Important: If a negative value is set in the offset tables as the tool radius,
compensation direction (tool left or right) is reversed for G41 and G42.
G41 and G42 are also reversed during the mirroring operation
(see chapter 14).
All of these G-codes are modal and belong to the same modal group.
Figure 21.3
Cutter Compensation Direction
Cutting tool
Entry move
G40 (no compensation)
G41 (compensation to left)
G42 (compensation to right)
21.1
Active Cutter Compensation