Center Thickness NOT Correct

To check the generated CT against the work ticket CT:

1. If using a generator that specifies thickness using "set value" or SVAL, measure the lens (while blocked) and compare the set value on the work ticket against the set value that is measured. 
2. If using a generator that cuts to center thickness, measure the lens (while blocked) and compare the measured thickness (compensating for the block) against the CT on the work ticket.  If necessary, measure the CT after polishing and deblocking, and compare to the "finished" CT on the work ticket.

If the center thickness (CT) of the lens after generating does NOT match the value on the work ticket, here are things to check.

Check to ensure the correct block was used.

In the case of equipment using SVAL (set value), the SVAL is calculated based on the lens blank and the block, so if a different blocking ring was accidentally used, the CT of the lens will not be correct.  To review, the SVAL is the height from the plane of the block to the back surface of the lens at the blocking center.  Since both the diameter of the block and the height of the block affect SVAL, if the wrong blocking ring is inadvertently used, the CT will be incorrect (and could result in cutter crash in some instances).

If the correct blocking ring was used, but the measured thickness still does not match the work ticket, it could be a calibration issue with the generator.  All generators have calibration routines and processes that can be run to assist in correct calibration.