Rockwell Automation 8520 9/Series CNC Integration Maintenance Manual Documentation Set - Manual (Page 175)

Section 4B
Connecting the 3-axis Servo Module
4B-29
There are two typical analog servo drive configurations for the control.
The typical mill configuration has three axes, each having a servo motor
and feedback device, and an open loop spindle motor. The typical lathe
configuration has two axes, each having a servo motor and feedback
device, and an open loop spindle motor with position feedback.
The analog servo module functions as a high speed servo processor. It is
installed in the component enclosure.
The analog servo amplifier amplifies the signal from the analog servo
module in order to deliver the power necessary to drive the servo motors.
Position and velocity data are read from a feedback device that is mounted
on the slide, ballscrew, or servo motor. This feedback device generates
differential signals that are then fed to the analog servo module. If the
spindle motor incorporates an encoder it will supply spindle position
feedback to the analog servo module.
4B.6
How the Analog Servo
Module Works