Operation and Maintenance Manual Model 7AF Wafer Grinder
2
Number: 10 Value: 0.0 Label: LT Chuck Home Offset
If you do NOT have rotational homing hardware installed, any value other
than zero will prevent you from operating the 7AF. With the value zero, an
attempt to home will be made, and when a full revolution is completed
without seeing the home pulse, that position will be called the home position.
With rotational homing hardware installed a value between 0 and 1 will cause
the left chuck to stop at this fraction of a complete revolution away from its
home position, measured in the counter-clockwise direction. Similarly a
value between 0 and (–1) will do the same thing in the clockwise direction.
In software versions 5.00-5.07, an out-of-bounds value, such as 2, would
request NO rotational homing during a grind cycle.
In software version 5.08, Rotational Homing “Sometimes” was added. This
keeps the range (-1) to (+1) as the “always” range for rotational homing.
The next range, consisting of (-2) to (-1) and (+1) to (+2) is the “sometimes”
range. Finally the outside range, smaller than (-2) and larger than (+2) is the
“never” range, requesting NO rotational homing during a grind cycle.
In the “sometimes” range, the chuck moves to its home offset position
whenever it has a wafer or is about to receive a wafer. This keeps the wafer
oriented properly. But when the probe is dropped onto an empty chuck, the
chuck is first rotated to a random position.
Rotational homing is necessary for grinding square wafers, so that they
maintain their orientation throughout the grind cycle and end up placed
correctly into the receive cassette. It is also useful if a customer installs a
work chuck that conforms to the shape of a round wafer, including the flat
side. The actual value for the home offset will vary slightly from 7AF to 7AF
due to mechanical tolerances. The correct value will be determined during
the assembling and/or installing of the 7AF.
By using the “sometimes” range you can help to prevent dents in the chuck
caused by the probe always dropping in the same spot.
Number: 11 Value: 0.0 Label: RT Chuck Home Offset
See the preceding description.
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