In some cases labs may wish to set up cribbing so that specific crib diameters are calculated. This might be the case when AR coating lenses, for example, where an AR machine has specific diameter requirements.
Specific crib diameters can be set up as a general default, as a default for lenses with AR coating, or specific rules can be set for a specific coating.
Cribbing groups are set up under "Setup", "Crib groups". A lab can have multiple cribbing groups, for example if certain crib sizes are needed for in-house AR, but a different set of crib diameters is required for an AR coating that is done at another lab.
For example, a lab might wish to crib lenses to specifically 62mm, 65mm, or 70mm for all jobs with AR on them. A default crib set might look like:
In this example, elliptical cribbing (ELLH) has been deactivated, so lenses will be cribbed only to a round shape.
Any lens with a crib <=62 will be increased to 62mm; from 62.1 to 65 will be cribbed to 65mm; from 65.1 to 70 cribbed to 70mm, and anything that calculates a crib larger than 70mm will be cribbed to the calculated size.
If elliptical cribbing is desired, but only to specific sizes, specific ELLH sizes can be put in for each of the specified crib diameters. For example, extending the above case, let's assume ELLH values for the 62mm crib can be 60 or 62; for the 65mm they can be 60 or 65, and for the 70mm crib they can be 60, 65, or 70. The group would be set up as follows:
