edging into plastic frames

[odod]

We have been having a little bit of trouble edging with our new coburn edger into the flexible or thin plastic frames. An example of this frame is Marchon 401 (thin) or Leah by Priority (flexible). The top of the plus lens just wants to pop out of the top and the lens doesn't stay in when the frame is bent a bit (which you know patients will do as life occurs!!) Any suggestions--should we be edging bigger or smaller--frame seem flatter than the plus lens....

odod
License Optician

[vcom]

I'm not familiar with that edger, but you should be able to adjust the bevel curve to match the frame curve. Plus lenses in a plastic frame are tricky sometimes, and it may be the thickness of the lens on the nasal side being pushed out by the nasal portion of the frame. Normally I had to do a little work on the hand stone, but most newer edgers should allow you to adjust bevel angles and curves. It can happen with minus lenses in plastic frames as well, usually on the temple side causing the arms to splay out, or the lenses to pop out.

I would edge some scrap/practice lenses and experiment. I've had some edgers I just always edged high plus lenses a wee bit smaller to avoid them popping out. Best answer is to experiment, every edger has a different tempermant and personality, you just have to get to know yours!

[Slim]

two things I do when that happens is take a lil off the "A" as the lens is to wide... but before that I match the curve of the frame to the curve of the lens in the warmer... then adjust the spay to your needs.

[PRECISIONLAB]

Most of todays frames seem to have a frame profile of 4 base. Couple of tricks to insure a correct fit

Most Plus stock lenses are processed on an ideal base curve meaning a +2.00 stock have a +8.00 BC and thick as well. Some manufacturers have stock lenses processed on flatter BC. K-Mars is an example. Thier +2.00 is on a 5.75 BC. If flatter stock isn't available consider grinding or ordering uncut with flatter curve and ideal thickness.

If your tracer has the option of shape modification, adjust B up by .2-.3. Doesn't sound like much but it does the trick. Always trace the DEMO for true shape

As mentioned by VCOM, edge in base curve or profile mode. The lens curve/bevel will match the frames profile or BC. Size accordingly and that should eliminate lens from popping out on the B side

[Craig]

Welcome to Optiboard. You can try ordering the lenses to match the frame Base Curve and most tracers still trace large. You can control the bevel on that edger and move it around, but the flat curves will help the most and then start taking the lens down slowly. We also try to steer high plus patients to a 6 base frame or a drill mount to avoid such issues on high RX's.

[Dave Metzger]

Welcome to Optiboard. You can try ordering the lenses to match the frame Base Curve and most tracers still trace large. You can control the bevel on that edger and move it around, but the flat curves will help the most and then start taking the lens down slowly. We also try to steer high plus patients to a 6 base frame or a drill mount to avoid such issues on high RX's.

Also sounds like the b is being squished when tracing. Trace the RT only keeping the demo in the left to maintain shape.

[standarduck]

Also sounds like the b is being squished when tracing. Trace the RT only keeping the demo in the left to maintain shape.

You could also experiment with tracing the dummy lens to get a good rendition of the shape if you think the frame trace is distorted (not uncommon in polypropionate frames)

[MIOPE]

It is true. Most of the frames come in this days with base 4.00 demo lens. Most of them are also straight on top closer to a rectangle shape. It is common to have plus lenses that will pup out on top. I think that the problem is related to frame shape more than edging problem. If you bend the frame to copy the curvature of the BC of the lens, later you will have the customer back with the lens puped out.
We solved that problem using aspheric lenses. Finished and semifinished including multifocals. Vision Ease has a ultra aspheric multifocal and others should also make similar products.

[Pogu]

When you are set to edge, measure the B before you take out the demo, measure again after it's been removed. If there is any difference, trace the demo lens and size down appropriately. This will leave you with no trace of the Z-axis (frame curvature) so make sure to clock the demo's curve and match as close as possible with the custom bevel options. Using the wrong base curve is a last resort, though with digital compensation is becoming a more viable option.

[Tallboy]

All these tricks, including the use of aspheric lenses, will help. I don't have a blocker that allows me to modify shape on my nidek edger, but I quickly achieve the same results by stretching out the B with my fingers a tiny bit prior to tracing and then squishing it back into its original shape prior to mounting.

[Barry Santini]

I have found that bevel matching is far more important that decreasing the difference.

B

[uncut]

OR...you can buy frames that are better engineered and designed to hold lenses, any lens...... Follow up with dispensing the appropriate lens shape, and size suited to the power of the lens being produced. There is a lot of effort at the edger to make a lens "fit". Whether all will stay in the frame as it ages and is subject to life is questionable.

I know this sounds harsh, but I see a lot of badly designed frames out there. Some of the designs are based on popular shapes, and materials of the past, but with modern errors in groove depth, position, and angle for the shape of lens.

[Pogu]

I find the effort at the edger satisfying. Some frames don't lend themselves to tracing, some lenses don't lend themselves to mounting, figuring out how to exploit the technology available has made my work both engaging and rewarding. Meanwhile I can expand the number of options available to our clients.

I'm curious which brands you find badly designed. I always have trouble with Oga from Morel, and a lot of metal men's frames from Signature are hard to get an accurate trace on as well.

[uncut]

Pogu:

I don't specifically recall a manufacturer or distributor that has model failures, consistently.........those typically got kicked to the curb along the way. I think every frame maker can and will design a "dog". We all have had that dreaded frame out there that constantly needs_______________________ ______ done to it!

The last two acetate frames I recall giving me grief had an extremely thin top rim coupled with battleship thick steel temples that forced the top rim to "flatten", and the other was attempting to be thin, except around the hinge imbed area. When glazed.....the temples splayed out wide enough to fit a watermelon, not the lemon that bought it. But............fashion dictates some decisions, and high heels in snow don't work, either!

[PRECISIONLAB]

Form vs. Function. I'm curious as to how frame designers consider the issues raised in this thread. Is fashion considered first then the technical design next or is it simply a mentality of make the circle fit into the square. Are lens manufactures or consultants used to detail what most experienced opticians on this board know regarding BC power limitations etc. based on frame. Perhaps these issues should be mentioned to your frame sales rep and explain why Frame X is no longer ordered and why Frame Y works. Savvy frame buyers usually can identify issues before the rep has a chance to pull the sample from the kit.

On the lab side, my staff knows to evaluate each frame and determine correct lens choices before it gets to edger.

[globaljp]

Match the edged lens curve as close as possible to the frame curve. When i first started edging i used auto mode. Now everything is manual so i can adjust the frame curve and move it forward or back. Fir is awesome now. just watch how much shelf you get on the front of the high plus, balance how much shelf may stick out the front with getting a matching curve.

[DanLiv]

two things I do when that happens is take a lil off the "A" as the lens is to wide... but before that I match the curve of the frame to the curve of the lens in the warmer... then adjust the spay to your needs.

If your tracer has the option of shape modification, adjust B up by .2-.3. Doesn't sound like much but it does the trick. Always trace the DEMO for true shape

OMG THANK YOU! I have an awesome me1200 and do great high wraps and shelf bevels, but often I get a little pop out on the top just like the OP, but even without that squeezing the top and bottom eyewire sometimes causes a little "creaking" like it doesn't fit perfectly, yet bringing the size down does eliminate that but makes the lens a sliver too small all around.


I tried both upping B and reducing A a little on a few pair to day and it's PERFECT.


I've been doing this for some years, but is so awesome to keep learning little, seemingly innocuous, tricks of the trade that make a huge difference. Feels like advancing to the next level of the inner circle of arcane knowledge!!


Thank you both. LOVE OPTIBOARD.