Rockwell Automation 8520-MUM 9/Series CNC Mill Operation and Programming Manual Documentation Set - Manual (Page 527)

Cutter Diameter Compensation
(G40, G41, G42)
Chapter 21
21-9
Besides choosing between types A and B (selected in AMP), cutter
compensation generated blocks can also be controlled by programming a
G39 or G39.1. These G-codes determine whether the generated block will
be linear (G39) or circular (G39.1) as shown in Figure 21.7.
G39(or G39.1);
Where : Causes:
G39 linear generated blocks. If neither G39 nor G39.1 is programmed,
G39 is the default. This command is modal.
G39.1 circular generated blocks. When cutting straight line-to-arc or
arc-to-straight line moves, the generated block will always be linear
and the G39.1 will be ignored. This command is modal.
Figure 21.7
Cutter Compensation Generation Blocks (G39 vs G39.1)
G39 (linear generated block)
End of
1st cut
Start of
2nd cut
r
r
r
block
generated
End of
1st cut
2nd cut
G39.1 (circular generated block)
r
r r
Linear
block
generated
Circular
r
Programmed
path
G42 tool path
Tool radius r =
Start of
G39 or G39.1 can be programmed in any block. However, they must be
programmed in or before the block that causes a cutter compensation
generated block.
Important: For linear generated blocks, the system installer can define a
minimum block length in AMP. If the generated move length is less than
the system-defined minimum block length, no generated block is created.
The tool path proceeds to the intersection of the two compensated paths. If
the generated move length is equal to or greater than the system-defined
minimum block length, a generated block is created.
Throughout this chapter, we show drawings where a generated block is
created. Both G39 and G39.1 are shown in these drawings where
applicable.