Strasbaugh Mechanical Description
Version 4.0 - February 1998 4 - 11
ROBOT ASSEMBLY
Supported by a slide assembly, the robot travels between the left elevators and
the right load station, stopping at each elevator and load station (a range of
approximately three feet). The slide assembly is comprised of two hardened
steel rails and a lead screw supported at both ends. On the right end of the lead
screw, a brushless DC motor is connected by direct drive through a flexible
coupling to the lead screw.
Four linear pillow block bearings mounted underneath the robot base slide on the
hardened steel rails. The lead screw is rotated within a stationary polymer nut
located underneath the robot base, causing linear movement of the robot.
Encoder feedback monitors position and speed.
The robot’s Z-axis provides up and down linear travel. Located inside the
rectangular housing, the Z-axis has a backplate mounted with three linear
bearings mounted on a spine shaft at the center of the housing. A stationary lead
screw (located inside a nut mounted in two bearings on the framework of the
robot) is rotated by a brushless DC motor driving a tooth belt and two pulleys,
causing upward and downward movement of the robot. Encoder feedback
monitors position and speed. The Z-axis has a single inductive sensor located at
the middle range of travel and functioning as a “home” switch.
The robot rotational (theta) axis is belt driven by a brushless DC motor (mounted
inside the robot assembly), two pulleys, and a tooth belt. An inductive sensor
located inside the housing “homes” the theta axis. Encoder feedback monitors
position and speed.
The robot radial axis (also belt driven by a brushless DC motor, two pulleys, and
a tooth belt) is mounted on a spindle located in the end of the theta axis housing.
The spindle is driven by two pulleys and a belt. The belt and pulleys are driven
by a shaft (driven by two more pulleys, a belt, and a motor) extending down
inside the robot assembly. An inductive sensor located on the underneath side of
the housing “homes” the radial axis. Encoder feedback monitors position and
speed.
The robot’s radial and theta axes permit it to reach into wafer cassettes and out
over the load stations, positioning an end effector located on the theta axis over a
wafer. The end effector is a vacuum chuck fitted into the end of the theta axis.
The vacuum chuck picks up and deposits wafers to and from elevators and load
stations. The end effector is equipped with a vacuum switch, located inside the
housing, to sense when the robot has taken vacuum on a wafer.
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