Strasbaugh Mechanical Description
Version 4.0 - February 1998 4 - 17
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.
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