Strasbaugh Machine Description
Version 4.0 - February 1998 2 - 33
CONDITIONING ARM DOWN FORCE
ASSEMBLY
The servo-controlled conditioning arm down force feature provides
programmable down force for the pad conditioning device.
The conditioning arm device assembly consists of a circular rotating device
(with programmable rotational speed) which applies a downward force upon
the polish table while being driven linearly by a linear drive DC motor from
the middle of the polish table to its circumference (or vice versa) for a
conditioning cycle. At the end of a cycle, the conditioning assembly parks
itself off the polish table to the right. A magnet in the linear drive
mechanism homes the arm, using encoder feedback to determine its inner,
outer, and park positions. A pneumatic cylinder at the base of the arm
assembly shaft raises the entire assembly to move the conditioning device
off the polish table or lowers it to apply a regulated downward pressure upon
the surface of the polish table. When the arm is at the table, a second air
cylinder, together with a load cell and an electro-pneumatic regulator, raises
and lowers the device itself, producing and controlling conditioning down
force. The second air cylinder’s function is programmable in software.
The load cell senses the amount of force applied and generates an analog
voltage signal proportional to the amount of force. This signal is amplified
and transmitted to the control computer through an analog input channel.
The control computer receives the information and compares it to the
programmed value of required device down force. The control computer
regulates the applied force by regulating the air flow to the air cylinder with
the electro-pneumatic regulator. The control computer generates an analog
voltage signal for the electro-pneumatic regulator, and the regulator adjusts
the air pressure in proportion to the voltage level of the signal. Together the
control computer, load cell, and electro-pneumatic regulator form a closed
loop controller to maintain the downward conditioning force within 2% of
the programmed force value in pressure mode.
The programmable functions of the conditioning arm are controlled at the
Sweep Parameters and Conditioning/Cleaning Parameters Menus.
To Next Page
Loading...
