Rockwell Automation 8520 9/Series CNC Lathe - Manual (Page 593)

Compound Turning Routines
Chapter 24
24-29
In the G75 casting/forging roughing routine (also called pattern repeating
routine), the control generates multiple cuts, each parallel to the workpiece
final shape. Each cut is offset from the other an amount determined by the
I, K and D parameters.
Through this process, a shape similar to the finished contour is obtained
when the routine is completed. At the completion of this routine a finish
allowance is usually left on the workpiece to be removed later by a G72
finishing routine.
Figure 24.23
Pattern Repeating Routine
Cutting feed
Rapid feed
(start point)
Z
X
Finishing pass
Shape defined by
workpiece contour blocks
Note: Tool paths not to scale.
The calling block references the sequence numbers (N-words) of the first
and last blocks of the contour blocks defining the final contour of the
workpiece. This set of blocks may be located anywhere after the calling
block (even after an end of program command), as long as the calling
block is in the same program as the set of contour defining blocks.
Contour blocks cannot be in a subprogram or a macro unless the calling
block is in that subprogram or macro.
24.3
Casting/Forging Roughing
Routine (G75)