Strasbaugh Pneumatic Adjustments
Version 1.2 - April 18, 1996 9 - 5
SPEED CONTROLS
The machine incorporates pneumatic speed controls to control the
cylinder rod speed wherever possible. These speed controls
consist of a needle valve paralleled with a check valve. This
provides for flow adjustment in one direction and free flow in the
other direction. Speed controls meter the air being exhausted from
the cylinder. The actuating pressure is free flow to prevent
cavitation in the rod stroke motion. In other words, when adjusting
a cylinder with the speed controls mounted on the cylinder each
control knob adjusts the speed of the cylinder as it moves toward
the control.
Cylinder speed controls are mounted directly on the cylinder
wherever possible. On newer machines all speed control is done
directly at the cylinder except for the door cylinder and pick-up
chuck which are not conveniently accessible. In these cases the
speed controls are mounted on the manifold ports.
Speed adjustments are made initially at the factory and should not
require frequent change. All speed controls should be adjusted for
smooth cylinder operation. In certain cases this must also comply
with machine software timing constraints.
The cylinder for raising the wafer under the measurement probe is
a tandem air/oil cylinder. The cylinder is operated using air
pressure to move the piston. The cylinder rod is coupled to a
tandem oil cylinder. The oil cylinder provides a smooth motion for
the rod stroke. Two speed controls are located on the oil line for
the oil cylinder. These controls function similarly to the pneumatic
speed controls. The cylinder speed should be adjusted so that the
rod travels the entire stroke length in two seconds.
Faster cylinder speeds may cause wafer breakage or exceed
the slew rate of the measurement probe resulting in
erroneous thickness measurement. Slower speeds will result
in the measurement being made while the probe is in motion
which will also result in erroneous operation.
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