Rockwell Automation 8520-GUM 9/Series CNC Grinder Operation and Programming Manual Documentation Set - Manual (Page 408)

Axis Motion
Chapter 12
12-36
If your surface grinding machine uses the S--word to control wheel spindle
speed, then CSS (programmed with a G96) and its counterpart RPM
spindle speed mode (programmed with a G97) are available.
When CSS is active during surface grinding, it maintains the surface speed
at the diameter of the grinding wheel at a constant rate. For example,
dressing the grinding wheel typically reduces its diameter. With CSS
active, the control increases the wheel speed proportional to the decrease in
diameter to maintain the surface speed of the wheel relative to the part.
When using CSS during surface grinding and wheel dressing, the wheel
spindle typically is selected as the CSS axis. CSS axis selection is
described on page 12-45.
Figure 12.20
CSS on a Surface Grinder
Magnetic table
Part
CSS on a surface grinder
maintains
a constant
speed between the part
surface and the grinding
wheel even as the wheel
diameter decreases due to
wear or dressing.
S
As wheel diameter
decreases,
wheel
speed increases to
keep surface speed S
constant.
S
12033-I
This is especially important on machines that perform in-process wheel
dressing or lose substantial amounts of wheel material with each pass. In
those cases, the change in diameter during a long grinding operation can be
significant. If the wheel speed is not adjusted (through CSS), then there
could be a noticeable variation in surface finish.
12.5.2
Surface Grinder,
S- word for Wheel Speed