I am working on a job with a semi rimless frame, a +RX with no cyl is causing a thick center and a super thin edge which is about impossible to set without chipping the lens. Using CR39 as the patient wanted no material upgrade. Is there a way I can alter some of the settings on the SGX pre-cut to possibly create a thicker edge? I am a bit new to the lab still. The OD came out perfect, but has a bit of cyl. Any help would be greatly appreciated!
Last edited by dave.fant.lab; 08-14-2012 at 04:20 PM.
Use thickness calc http://www.opticampus.com/tools/thickness.php, Specify center thickness enter as metal edge, this should produce a 1.0 thin edge, add 1mm to center, this will produce the thinnest possible ct with a 2.0 edge.
You're awesome sir, a life saver hah. Thank you very much.
Your lab software should account for thickness based on frame type entered. For example if a rimless is specified minimum thickness will be 2.2. Tracing the frame and importing the frame data will always produce desired thickness. Since this was cr -39 and the result was a thinner than desired lens, perhaps defaults are incorrect or frame size was not correct. What type of lab software are you using?
Very true about frame measurements, but I find that specifying center thickness gives you greater control over thickness. For example, if you're surfacing a polarized lens, you have to make center a few tenths thicker because if you don't you will get clear edges. You have to pay your dues with surfacing! Pay attention to what your doing and don't make the same mistake twice. It's kinda fun when you really get into it. Good luck to all.Originally Posted by PRECISIONLAB
Plus power semi-rimless jobs are always run at least 1 mm thicker than a normal mount. Are you perhaps not using an integrated layout/generating software? Or it doesn't have an option for frame designs or modifying CT?
My lab software usually over compensates for rimless thickness. I usually have to take some off in the generator to get the thickness correct. The longer you work with your machinery and lab management/ calculation systems the more you will learn their peculiarities and nuances, there will be a few stumbles on the way.
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We use Innovations. I trace the job into the system which conducts a lot of the measurements and I manually input the setting as a semi rimless. I set it as a 'groove' in new job creation as far as frame type, beyond that I do not encounter anything that is specific about the type of frame I am using for the lenses. If there is some kind of default setting I can adjust for groove to make the edge a bit thicker I am unaware of it. I had 1.5 days of training in the lab, with no prior optical experience, I've been doing it for about 3 months now. I run into some issues from time to time which Optiboard has been a great forum for information and assistance, but otherwise I have been doing decently well all things considered. We all start somewhere I guess. Again I greatly appreciate all the help, thank you.
I also now have a permanent mental note about the + power semi rimless, thanks. This is the first job I've encountered like this so far.
Yes, you can adjust the minimum thickness on a job-by-job basis, but that should not be necessary. If your equipment can't handle knife edges, you can set a minimum thickness at the crib perimeter (that's frequently used for freeform). The edge thickness is automatically increased when you select the "Groove" or "Nylor" frame type, if those are set up properly - someone may have changed the default settings.
You really should not be having a serious problem with knife edges on an SGX - it may not be operating properly. You would probably do well to have a Coburn tech take a look at your equipment.
With regard to the software, the best thing for you to do would be to contact our support team at 866-233-LENS (5467) when you have questions.
When you say the lens is "about impossible to set" - do you mean mount in the frame? Or do you mean groove? How thick is the lens at its thinnest point around the edge?
The edge on the original lenses was ~1.33mm, this is a new machine. We have had it for about a week, a Coburn Tech set it up. In reference to the impossible to set comment, it was meant in regards to setting the line in the groove due to how thin the edges of the groove are.
OK, call support. They know how to help you with thickness issues.
When I first started in the business in the early 80's thickness was varified as you generated on a manual machine such as a 108. Rule of thumb was desired edge plus or minus diopter power @ principle meridian. For example, if we wanted to varify center thickness for a plus lens I would caliper edge @ MBS..say 58 mm. So if I had a 2.2 edge with a +1.00 ct=3.2 or 2.2 edge with +2.00 ct = 4.2 and so on. The same was true for varifying prism..one diopter of prism would be varified if I had 2.2 on apex and 3.2 on base. Just wanted to share how we old timers did it before modern CNC machines. I suppose a simple glance @ the work ticket would give all the thickness settings.
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