Operation and Maintenance Manual Model 7AA Wafer Grinder
3 - 4 Version 1.2 - April 18, 1996
Line voltage is stepped down through a 2:1 750 VA transformer to
supply the AC voltage to power a rectified DC bus capacitor on the
servo amplifier. Also, line voltage is connected to the fan/bias
power connection on the servo amplifier. This power supplies the
amplifier cooling fan and internal + 5 and + 15 VDC power supply.
SERVO CONTROL LOOP
The machine contains two closed loop servo axes. One axis
controls the motion of the work chuck carriage and is designated
as the X axis (Axis 1). The other axis controls the feed mechanism
for the grind spindle and is designated as the Z axis (Axis 2). Each
axis contains several critical components required to perform the
motion control functions.
The resolver is a rotary device that receives excitation signals from
the digitizing reference module in the card cage and provides a
feedback signal to the microprocessor digitizing module. The
microprocessor digitizing module converts the feedback signal to
digital position information to be used by the control software. The
software routines compare actual motion to desired motion and
provide a command value to the digital to analog (D/A) converter.
The D/A converter provides a DC voltage (0 to +10 volts)
proportional to the command value.
This command voltage is connected to the servo amplifier. The
servo amplifier has two separate modules, each of which drives
one axis. The amplifier produces a pulse width modulated signal
proportional to the command voltage to drive the motor at the
correct speed. A DC tachometer coupled to the servo motor
produces a DC voltage proportional to motor speed. This
tachometer is connected directly to the servo amplifier to provide
tachometer loop compensation for stabilizing the velocity loop of
the motor/drive circuit.
24 VDC INPUTS
The control uses 24 VDC inputs for evaluating the on/off status of
limit switches, vacuum switches, proximity switches, etc. Each input
consists of an led and series resistor. When 24 volts are across
the input terminals sufficient current will flow to illuminate the led
and turn on the input.
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