Rockwell Automation 8520 9/Series CNC Lathe - Manual (Page 591)

Compound Turning Routines
Chapter 24
24-27
6. A rapid traverse is made back along the X and Z axes to the X
coordinate that the last rough cut started from (in step 3) and a Z
coordinate that is D distance above the Z coordinate of the last rough
cut.
7. A rough cut is made at feedrate F, into the workpiece parallel to the Z
axis to the Z coordinate of the last rough cut.
Steps 2 - 7 continue to repeat until the operation is aborted or the contour
shape is completed. The contour shape is completed when the thickness of
the material remaining to be removed from the contour is equal to the sum
of the finish allowance (U+W)/2 and the final pass allowance (I+K)/2. If
no final pass is to be cut, skip to step 9.
If a final pass is programmed in the G74 block (I or K values in the G74
block) it is not executed until all of the workpiece pockets have been
completely roughed out.
8. The final pass is made at the feedrate programmed in your contour
block including any rapid moves (if no feedrate is programmed in the
contour blocks, the control uses the F-word programmed in the G74
block). Only the amount of material specified with the final pass
allowance (I+K)/2 is cut. This cut is made parallel to the exact
contour of the final workpiece, it is not a roughing pass. After this
cut is complete, the only material remaining on the workpiece contour
is the finish amount (if any) as programmed with U and W.
9. The control returns the cutting tool, at a rapid feedrate, to the start
point of the cycle.
Example 24.6
Case 2 G74 Rough Facing Routine
N011 G00X128.Z120.;
N012 G74P14Q21U.6W.6I.8K.8D10.R7.F10.S60;
N013 M30;
N014 X120.Z110.;
N015 X100.Z30.;
N016 X80.;
N017 X70.Z70.;
N018 X60.;
N019 X50.Z50.;
N020 X30.;
N021 X20.Z107.;