Printable View
Hello, I work for a small optical lab and we have had consistent issues with a specific frame. With any lens on a base curve over a 4, the top of the lens will always pop out of the frame when you flex it a little. do any of you have some tips or tricks on how to get it better seated in the frame to keep this from happening?
Add a little to the "B" measurment..
we did that. it worked well with the lower base curves but once you get beyond a 4 BC they just wont stay in there. at least not without some extreme frame manipulation.Quote:
Originally Posted by Fluegge Optical
What material is the frame made
And what material are the lenses made of? This is a not-uncommon problem with zyl frames and low-minus polycarbonate lenses. The poly is somewhat flexible, so it will bend if it's edged just a little too big.
I will cut the lens a bit larger and then take some off the temporal and nasal side on the hand stone which will make the lens more narrow in the A but it will be deeper in the B.
Frame is ZylQuote:
Originally Posted by Lensman11
the frame is zyl, and the it seems to happen with all lens materialsQuote:
Originally Posted by AngeHamm
The lens must be cut to match that frames base curve and only in a stiffer material like trivex or 1.6.
Someone in the past explained it this way-
Think of the lens surrounded by a piece of string which is the frame- as soon as you create any tension the string inevitably will straighten. Same thing is happening to the frame unless the base curves match.
fwiw- You should ask a moderator to move this to the general discussion forum where more eyes will see it.
that all makes sense. is there an easy way to do that? We have an Alta NX edger. I have played with the settings for a few hours trying different things, but i dont see a way to do that.Quote:
Originally Posted by Uncle Fester
Also, im not quite sure how to go about that last bit.
At the bottom of our posts is a line that starts "Blog this Post". Click on the little triangle next to it- then the "report thiis post" drop down and ask to have this thread moved to general discussions by a moderator.
Lab techs who are familiar with this edger may be able to tell you how to adjust it for a specific base curve setting.
Ordering the lenses uncut to the frame base curve is the way I usually do it but that has some limitations as well.
If you carefully hold a lens clock to the top of the frame front you should be able to measure the frame base curve.
Sometimes jobs like this are best sent to a large lab who have multiple different types of edgers and can edge it better.
Zyl is a generic term for plastic. Some frame materials do lend themselves to be reformed on curvature. Two ways to help. Put a 4 bc on the bevel curve as previously suggested or restrict the bc of the lenses for that frame. Yes it would mean surfacing lenses that would normally be stock. You might also look at the demo lenses that are in the frame if they are 6 bc which most are and they don’t flex you have another problem. Accurately measure the a and b measurements of the demo and make sure you have the same ratio in the lenses you are making. You might also look at the groove on the frame, some frames have the back higher than the front no allowing the lens to seat in the groove if this is the case you need to use a step bevel to clear the back of the frame.
I find stepping the backside like Lensman said and increasing thickness of the bevel slightly solves this issue very well, but that is if your edger has those capabilities. All of the suggestions in this thread work.
Also a little latex interliner can help if you don't have variable bevel / step bevel capabilities
Do you have the option of just not carrying that frame any more? I assume since it's coming up regularly that it's a frame coming from an attached dispensary. I've done that in a few cases with frames that were just poorly designed or too troublesome to be worth the hassle of edging for them. There was a Coach frame about 10 years ago that would snap in two if you put poly lenses in it and cleaned it with alcohol. Happened every single time. Just one frame model.
Unfortunately that is not an option. The frame comes from the company owned by our CEO, and is considered to be one our "core" frames. So we will have them around for a while.Quote:
Originally Posted by AngeHamm
Don't know much about frame manufacturing but I wonder if there is a way for you to mention this issue to the higher ups so it can be addressed.Quote:
Originally Posted by Dooky Shoes
If it's happening to you it's happening to all and others may be able to suggest how to keep the shape but fix the problem.
I'm thinking a better bezel design in the molding process assuming it's a cheap injection molded process.
Step bevel and/or inclined bevel works well, if your edger is capable. Another option is to add a little to the B on your tracer. Most tracers will allow you to set this in the default menu. I set ours to add B and subtract A. This, in conjunction with step/incline has helped a lot.
Having the difficult conversation with your CEO regarding the frame quality, and it’s difficulties would be a necessary conversation, as well.
I am curious as to what tracer, and edger that you are using?
I push the bevel forward and use variable bevel mode on my edger making the back edge slightly longer than the front and matching the base curve of the frame to the bevel if possible.
My typical go to settings for problematic frames is front bevel 0.8mm/rear 1.0mm or 1.1mm. If I cant match the bevel curve to that of the frame, I will use the 4:3 ratio setting on my edger. This is on a santinelli lex-1000 and ICE-1200 blocker. I used to deal with this issue alot and did a fair amount of experimenting until I found a solution that works 95% of the time.
Also, the installing technician that set up our edger set it up to automatically add a little to the B measurement to reduce squeaky lenses.
I've found this works well. Also observe your tracing process. Does it have a shallow B and rectangular shape? Make sure you aren't squishing the frame when you close the clamp during tracing otherwise you'll have to use lensman's method or trace the demo lens.Quote:
Originally Posted by lensmanmd
Run the bevel to the front
send it out lol
mess about with bevel placement if you can
sounds like you have to mess with it and find a template for that particular frame