Rockwell Automation 8520 9/Series CNC Lathe - Manual (Page 416)

Spindles
Chapter 17
17-18
mode. If the AMP parameter Automatic Home on Virtual C Entry is
set to “NO” (refer to the documentation provided by your system installer),
you need to home the virtual C axis, typically by programming a M19S0.
The control positions the tool on the cylindrical work surface with two
distinct moves. In the first move, all programmed axis moves in the initial
G16.1 block (including the C axis) are executed. This move takes place at
the rapid feedrate for the axes.
In the second move, the feed axis (X) is moved at the active cutting
feedrate to the radius specified by R.
The blocks following the G16.1 block determine the contour to be
machined on the side of the cylindrical workpiece. The moves of the
virtual C axis and the machine axes are interpolated to produce the
programmed contours.
The following example makes a circumferential cut, followed by a 90
degree arc, followed by a linear cut, all made into the side of a cylindrical
workpiece. The C axis angle in the G03 block of this program was derived
from the equation that follows this example. Figure 17.4 illustrates the
results.
Example 17.2
Virtual C Axis, Cylindrical Interpolation
N1 G91 M05;
N2 G16.1;
N3 C10. Z-40.;
N4 C60.;
N5 G03 Z8. C18.335 R8.;
N6 Z20.;
N7 G16.1 R30.;
N8 G15;
The angle for the C move in the G03 block above was determined by using
this equation, with L = 8 and R = 25.
360 ( L )
q = -------------
2 p ( R )