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Introduction to the Rotate Theta Stage

This document will help you get started with your new rotate stage. It can be mounted on either an FTA188 or FTA200.

The rotate theta stage will hold up to 8 inch, 200mm diameter wafers or similar specimens. It is normally used to obtain contact angles around the circumference of the specimen.  It can be positioned radially from the camera so the circle of inspection has a radius from zero, the center, to the radius of the sample. Delrin clips will hold a wafer in place and off the surface of the stage. A 300mm diameter stage is available on special order.

Rotate Stage mounted nn an FTA188

Rotary stage mounted on an FTA188.

Connecting the Stage to the Computer

The stage is driven by a controller box connected to the computer through an RS-232 port. The controller box is powered by an external 12V universal table-top power supply that accepts any voltage from 100 to 240VAC. There is no on/off switch and the controller can be left powered. The stage will not move when power is removed because of the gearbox on the motor.

The following connections must be made:

  • D9S cable from the rotate stage plugs into D9P connector on the controller.

  • RS-232 D9P cable from computer serial I/O plugs into D9S connector on the controller.

  • Power supply circular jack plugs into mating connector on the controller.

You must check the Rotate Theta Stage option in the Hardware portion of the LogOn screen for the software. Your choice will be remembered, so it only need be done once. You must select an available RS-232 port for the serial line on the same screen.

The rotate stage is controlled from the Stage | Theta tab in the Fta32 software.

There may be additional connectors on the controller box if other accessories are driven by it.

Setting Up the Stage Mechanically

The sample platter is fastened to the motor adaptor with an M6 flathead screw. You can remove the platter to mount specimens or to substitute your own chuck on the motor drive.

The platter must be positioned radially and in height. The motor and platter ride on a rack-and-pinion Z stage which is adjusted manually. The radial position of the entire assembly is adjustable with the screw slots on the baseplate mounting surface.

Software Setup Constants

Motor parameters are setup on the Stage | Theta tab. The most important of these is the Gear constant which sets the number of controller steps per degree of rotation. This value should be considered the calibration constant for the stage: the stage will move the desired distance and at the desired rate only if this number is correct. The correct gear value is 160 steps per degree

The recommended maximum rate is 30 degrees per second, but normal operation is more typically 5 or 10 degrees per second.

The stage does not have a home sensor, but will remember its location when power is removed or the software shutdown. “Home” can be defined as any readily identifiable physical position. Home offset is the distance from that position to zero degrees rotation.

Software Operation

The Move command is the command used in ordinary operation. You specify the rotate increment, e.g., 45 degrees, and the rotate rate, e.g., 10 degrees per second, on the Stage | Theta tab. If you want the stage to go the opposite direction, you specify a negative increment. The Stop command can be used as an emergency stop of movements.

The Home command will return you to the zero location.