Rockwell Automation 8520 9/Series CNC Lathe - Manual (Page 501)

Tool Tip Radius Compensation (TTRC)
Function
Chapter 21
21-17
If the last programmed move is circular (an arc), positioning the tool at
right angles to a tangent line drawn from the end-point of that circular
move.
Figure 21.12
Tool Path for Exit Move Arc-to-Straight Line
Start-point
Start-point
Start-point
Start-point
Programmed path
Programmed path
Programmed path Programmed path
G41 G41
G42
G42
G41
q
r
r
q
r
r
G41
G42
r
r
q q
G42 r
r
0 £q £ 90 0 £q £ 90
0 £q £ 90 0 £q £ 90
The examples in Figure 21.11 and Figure 21.12 assume that the number of
blocks that do not contain axis motion, in the currently selected plane,
follow the G40 programming before an exit move takes place and does not
exceed an amount selected in AMP by your system installer. If the number
of non-motion blocks following G40 exceeds the limit, the control
generates its own exit move. This may often cause overcutting of the part.
You can modify the path that the tool takes for an exit move by including
an I- and/or K-word in the exit move. Only the I- or K-words that
represent values in the current plane are programmed in the block
containing the exit move. I and K correspond to the X and Z axes
respectively.