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For each job, "default" thicknesses will be determined, based on the power of the lens, the type of frame edge, and the lab's preferences.
On the "Thickness" tab on the material screen, the lab can specify the default thicknesses thickness parameters for minus and plus lenses:
uncuts and jobs with frame measurements:
(Thickness defaults as defined in versions 6.47.00 and later).
The "Default CT" is the center thickness used for minus lenses.
The "ET @ Plano" is the desired edge thickness of a plano lens.
The "Minimum ET" and "@ Power @ Min ET" go together, since the minimum edge thickness occurs at the specified power.
So in the above example (with frame measurements), a plano lens would have an edge thickness of 2.0, and a +7.00 lens a minimum edge thickness of 0.8mm.
The relationship of minimum edge thickness to power is linear, so a lens of +3.50 power would have a minimum edge thickness of 1.4mm. The minimum ET of any power can be illustrated with a graph:
For uncuts (with no frame measurements), beginning in version 6.47.00, different default thicknesses can be set for uncuts based on the uncut diameter.
In the above example, the default ET will be thinner the larger the uncut diameter is.
"Sum Of Thickness" is a parameter that allows an overall thickness to be specified for low-power lenses. If Sum Of Thickness is set to a value other than 0, then the CT plus the minimum ET must add up to "Sum Of Thickness", and if not, the thickness of the lens will be increased to make that condition true.
If the lens requires thickness to be added to satisfy the "Sum of Thickness" condition, this will be printed on the work ticket:
Finished Lenses
When considering finished lenses for blank selection for plus jobs, Rx-Universe will look at each finished lens, and calculate what the final edge thickness will be, for the frame and Rx, using each finished lens. If the lens has an edge thickness within a specified tolerance, then it will be deemed acceptable, otherwise it will be rejected, and blank selection will consider the next possible lens.
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When considering finished lenses, the center thickness is already fixed, so Rx-Universe will take that CT, and using the front curve of the lens, calculate how thickness thick the lens will be at the thinnest edge point on the frame.
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The 65mm blank will result in an edge thickness that is 2/10 0.2mm thinner than the desired 1.5mm ET, and the 70mm blank will result in an edge thickness that is 4/10 0.4mm thicker than the desired 1.5mm. Neither lens will give exactly the desired edge thickness, but a lab may decide that 2/10 0.2mm thinner is acceptable, or that 4/10 0.4mm thicker is acceptable, or that both (or neither) are acceptable.
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