'Wet bench' robot systemsThe ST wet bench robot system comprises an R15 Cartesian robot specially prepared for cleanroom work. ST robots are clean to class 100 even with no preparation. They can be prepared down to class 1 by special order.
Basically the robot comprises a linear track along the length of the bench with a moving carriage to which is mounted the Z axis then the Y axis is mounted to this and extends over the baths. The Y axis has a drop arm with the end effector on the end of it which is usually just a hook. For silicon wafer cassettes the end effector is shaped to match the cassette. Often a programmable Y axis is not required at all if all the baths etc. can be in a line. In this way the robot is both cleaner and cheaper.
The X-Z-Y or X-Z format means that the motor drives are positioned over the track and not over the work area. The pictures show a 5-axis robot with micro-stepping direct drive pitch and roll. Laminar air flow should ensure no contamination from the robot. The linear axes are driven by steel reinforced polyurethane toothed belts. The standard 3m belts are replaced by 2.5mm pitch polyurethane belts. Aluminium parts are either hard anodised (natural) or powder coated and stainless steel fixings are used. The whole robot is class 100 standard at this level. Each axis can have "dust covers" (bellows) fitted which are made of nylon/hyperlon laminate which does not shed. For even cleaner work we have a scheme whereby the robot is mounted behind a screen and reaches over the screen with a stainless stell tube.
SoftwareThe robot controller is easily interfaced to a PLC and other equipment and can even control valves etc. while the robot is in motion. Simple scheduling software facilitates more than one sample being passed through the system at a time.