Edger Wheel Pressure (EPRESS)
- Tony LeBlanc
Overview
Newer edgers have the ability to request the wheel pressure to be used from the lab management system. This parameter (called EPRESS in the VC communication standard), has 5 possible values:
0 – undefined
1 – very fragile (little pressure)
2 – soft pressure
3 – medium pressure
4 – high pressure
Labs can set a variety of parameters within Rx-Universe to automate the value sent to the edger. In this way, the lab can reduce breakage due to slippage and other issues on the edger, without requiring lab staff to remember to change edger settings.
Parameters Affecting EPRESS
Rx-Universe offers the ability to set EPRESS values based on the following factors:
different default values for each material
specific value if the center thickness of a lens falls below a user-specified threshold, per material
specific value if the edge thickness of the cribbed blank is greater than a threshold value
specific value for a lens style
specific value for a pretreatment (such as hydrophobic AR)
specific value for any addon (AR coating, mirror coating, etc.)
specific value for a frame type
specific value for a pattern record
When a job is requested at an edger which asks for the EPRESS, Rx-Universe checks each of these parameters for the order, and the LOWEST value for EPRESS is sent to the edger. Thus, if a job had settings similar to:
Material EPRESS = 3
Addon EPRESS = 2
Lens Style EPRESS = 4
Pretreatment EPRESS = 2
Frame Type EPRESS = 3
Pattern Record EPRESS = 0
The EPRESS would be sent as 2 for the job. If there are no EPRESS values set at all, a value of 0 would be returned to the edger, indicating the setting is undefined in the LMS.
Setting EPRESS by Material
The Material file allows a lab to set a default value for the EPRESS, a threshold for Center Thickness, and a different EPRESS value for lenses with a finished CT below that threshold; and an edge thickness threshold, with a different EPRESS for lenses which have an ET anywhere on the lens, at the cribbed diameter, greater than the threshold.
On the “Device fields” tab of the material screen:
Default EPRESS – is the default pressure which would be used for this material.
If center thickness (CT) is less than “X”, then use EPRESS “Y” – this allows the lab to specify a center thickness threshold, and if the CT of a lens is less than that value, to send a different EPRESS value. In the example above, if the finished CT of a lens is below 1.3mm, an EPRESS of 2 would be sent to the edger.
If ET greater than “V”, use EPRESS “W” – this allows the lab to specify a maximum edge thickness for the cribbed blank, and if any point on the edge is greater than the threshold specified, to use the EPRESS specified. In the example above, if the ET of the cribbed blank is above 12.0mm, an EPRESS of 1 would be sent to the edger. (See note about cribbed diameter later in this document).
Setting EPRESS by Lens Style, Pretreatment, Addon, Frame Type and Frame Trace record
A flat top 45 bifocal could be set up with a "soft" setting (2) because of the large bifocal size:
A slippery pre-treatment could be set up with a "soft" setting to reduce the change of the lens "slipping" on the finish block.
A particular frame type can be set up with a specific ERESS value:
In the example below, a particular frame trace can be set up with a specific EPRESS setting:
Minimum ET of cribbed lens
In order to check edge thickness at the cribbed diameter of the lens, Rx-Universe saves the crib diameter sent to whatever generator was used to generate the job. Because minimum crib size can be different for different generators, and some generators do not crib, this can be different for the same job if done on different equipment.
For reference purposes, the crib diameter that was actually sent to the generator is saved (called "Actual CRIB") and can be viewed by the lab, on the device information screen, for example:
For each eye, the screen shows the actual crib diameter, and the Max ET that was calculated for that lens at that diameter.
NOTE: if a generator operator over-rides the crib value sent by Rx-Universe in any way, the resulting edge thickness calculation for EPRESS will NOT be accurate.
Change DIA on edger
Some edgers expect to receive the cribbed diameter of the lens rather than the original blank diameter, in the field designated for the original blank diameter (this is the DIA label in VCA parlance).
For these devices, there is a checkbox on the device setup screen, whereby a lab can specify, for a particular device, to substitute the cribbed diameter (if applicable) when the device requests the DIA VCA label.
