Reverse Blank Selection (Shamir)

3.1 “Reverse” Blank Selection

Rx-Universe supports selecting the largest blank first for digital designs.  This approach can be used with the Shamir Prescriptor, where Rx-Universe will pick the largest blank that could be used; the Prescriptor will send back the smallest diameter and thinnest blank thickness that could be used, and Rx-Universe will re-select the blank, if possible, based on these criteria, when processing the LMS file.

Normal blank selection rules would select the smallest blank first, and submit it to the Prescriptor.  Then, if the job could not be run on that blank (either because of size or thickness), the Prescriptor would send back an error, the lab would manually select a different blank on the order, and resubmit the job.  This process would continue until the job was calculated successfully by the Prescriptor, or the lab had no other blanks to use.

To avoid the need to reselect blanks and resubmit jobs to the Prescriptor because of blank size or blank thickness, Shamir sends back a minimum diameter and minimum blank thickness in the LMS file.  In this scenario, Rx-Universe will pick the largest blank first, the Prescriptor will send back a minimum diameter (MINDIA) and a minimum blank center thickness (MINBCTHK) in the LMS file.  Rx-Universe will then check the inventory to see if a blank exists that is smaller than that originally selected, with the exact same front and back curves, and which respects the MINDIA and MINBCTHK – if such a blank exists, it will be used, with appropriate inventory adjustments made to the origjnal blanks.

An example might help to illustrate how this would work.  Take 3 lenses available from manufacturer SHAM, as follows (note that all have the same front and back curves, but different diameters and center thicknesses)..

When a job is created in Rx-Universe which uses this SHAM design, Rx-Universe will select the largest blank (the 85mm blank) first, and send that information over to the Prescriptor.  In the resulting LMS file created by the Prescriptor, the file specifies MINDIA=74 and MINBCTHK=7.0.

Using the MINDIA and MINBCTHK sent back, Rx-Universe will then check the lens blank inventory, looking for blanks from the same vendor that are smaller and/or thinner, which could work instead of the 85mm selected. 

When checking the 70mm blank, the lens is smaller than MINDIA, so it is rejected.  Rx-Universe next checks the 76mm blank, finding that it has the same front and back curves as the 85mm blank originally selected (and used for the Prescriptor calculations), and also respects the MINDIA and MINBCTHK sent back from the Prescriptor.  Rx-Universe will thus substitute the 76mm blanks in this job, making the appropriate inventory adjustments to reverse the 85mm blanks.  Since the front and back curves are the same, the calculations done by the Prescriptor to produce the SDF and LMS files are still valid.  The lab thus avoids selecting the 70mm blank first, and having to manually select the 76mm blank after the Prescriptor rejects the first submission, and resubmit, improving the turnaround time for the job and reducing manually modifications of the order.

Use of this “reverse” blank selection logic can be triggered for specific combinations of lens style and material – when selection from one style to another is used (for selection of corridor length based on seg height), the presence of “reverse” selection at any step will cause reverse selection to be used for the job. 

To trigger reverse selection for a particular lens design, check the appropriate checkbox in the alias setup for that design::