Rockwell Automation 8520-MUM 9/Series CNC Mill Operation and Programming Manual Documentation Set - Manual (Page 546)

Cutter Diameter Compensation
(G40, G41, G42)
Chapter 21
21-28
It is possible to modify the path that the tool takes for an exit move by
including an I, J, and/or K word in the exit move. Only the I, J, or K
words that represent values in the current plane are programmed in the
block containing the exit move. I, J, and K correspond to the X, Y, and Z
axes respectively.
The I, J, and K words in the exit move block define a vector that is used by
the control to redefine the end-point of the previously compensated move.
I, J, and K words are always programmed as incremental values regardless
of the current mode (G90 or G91).
The vector defined by the I, J, and/or K words is along a line drawn from
the end-point of the programmed path a distance as designated with the I,
J, and/or K words. The I, J, and/or K words must be in the currently
defined plane.
A new vector is then defined parallel to the vector defined by the I, J,
and/or K word and offset from this vector in the direction and amount of
the currently active offset (G41 or G42). The intersection of this new
vector with the current compensated tool path define a point which is the
new end-point of the last programmed compensation move.
Figure 21.23
Exit Move Defined by an I, J, K Vector
Compensated path using I, J vector
Compensated path if no I, J in G40 block
Intercept line
I, J
Compensated path
Programmed path
r
r
Exception is taken to the above figure when the change in length of the
compensated path is more than one radius of the tool. In this special case,
this offset is limited to one radius of the tool. The direction of the offset is
towards the point of intersection of the I, J, or K vector and the current
compensated tool path.