Lenses continue to pop out

[OPTICALWARRIOR]

Can anyone tell me why do lenses pop out of the frame vertically?

[chip anderson]

Lenses are the wrong dimension for frame.

[HarryChiling]

If the frame profile is flat then an asperic lens is going to seat better, I find that most of the time this is the case.

[THE MEB]

I have found, when this occurs, many times it's because the lens is a little wide horizontally. If you have a hand edger, taking a little off the bevel both in the temporal and nasal area will help prevent the lenses poppoing out vertically. Obviously, if you take too much off you will need to add a little lens washer.

[hipoptical]

I have found, when this occurs, many times it's because the lens is a little wide horizontally. If you have a hand edger, taking a little off the bevel both in the temporal and nasal area will help prevent the lenses poppoing out vertically. Obviously, if you take too much off you will need to add a little lens washer.

I agree... this usually is due to a bad tracing. There are a lot of frames out there that distort when the demo lens is removed. If you notice this happening on particular frames (Revolution is the worst) then trace the demo lens or request patterns. If it is on all frames you do, then check your tracing procedure and make sure that there is not too much pressure put on the frame. In both of these cases, the frame is widening while the "B" becomes smaller. You will hardly notice it by looking at the frame, but it happens. You edge to that shape and try to insert it, but there is nothing to hold it in at the top. Sometimes taking some off the temple and nasal will work, but starting with a good shape is best.

[OPTICALWARRIOR]

Thank you ,thank you ,thank you
i have tried to tell the guys in the shop we have a problem with our machines.tracers or edgers.now i will have to pass it on

[hipoptical]

Be careful...
I believe your issue is more with flimsy frames than with equipment. Try that first. If it is an equipment issue, the problem will be with all frames, regardless of brand, style, or material. My guess is that your problem is is most likely your process- you need to change your method of tracing due to the quality of frames you are dealing with.
(But please let us know what your findings are...)

[HarryChiling]

I would guess that the issue presents itself more so on the smaller frames with large A size to B size ratios like everyone here is talkign about if you were to take a lens clock and clock the frames eyewire from the front you will more than likely notice that the frames curvatures is in the lower base curves 1 to 4 base is the majority of what I see, times have changedframes used to have an averge 6 base lens which suited spherical lenses better. Using aspheric lenses that are flatter in profile will without a doubt eliminate this issue of course it requires that you inform your patients of their choice when they select certain frames. I like to tell patients that the newer stylish lenses require newer more stylish lenses. Aspheric lenses are almost a must now adays and the small investment in better lenses in this category will improve the qulity of jobs coming out of your lab as well as increase your bottom line.

IN a nutshell it is the dispensers job to inform th patient of the correct options to make a cosmetically correct pair of glasses, if the patient choses otherwise then it's the labs job to tryand make it work with tricks such as modifying the tracings (inovations software has this option), tracing patterns or demos, and shaping the frame.

[Refractingoptician.com]

Be sure to use the right edger to cut these jobs as well . The edger must be capable of base curve compensation . It must have the ability to edge the base curve of the frame onto the curve of the lens. If you can also match the width depth and angle of the frame bevel onto the lens , that wil also help to establish a better "bight" .

Most of these problems are due to putting a plus power lens into a frame with a very straight top frame rim combined with a shallow "B' measurement that gets bent out of shape by tracer pressure.

The Elision tracer out of Saskatchewan seems to put the least pressure on a frame.

Smaller grinding wheel diameters also can be a benefit .

[JRS]

Before you completely condemn the tracer, and/or edger, remember that most tracers measure RADII in a straight line.

So when the lens curve and the frame curve are not equal, there is a disparity when you bevel the lens to the lens curve (across the front). Idealy, in those situations, if you bevel to the frame curve – all is in alignment. You can easily demonstrate this with your tracer by tracing the frame as is (usually a new frame is around a 4.50 curve) and reviewing the A,B,ED,and CIRC. Then bend the frame to close to the same as the lens you intend to use, and trace it again. Compare the two example outputs from the tracer.

There is a complete math calculation to make all the proper changes to the RADIAL points when you are beveling in this fashion. Some of the more complex edgers – when aligned with the same vendor tracer, handles this automatically.

[Uncle Fester]

Low power poly lenses can flex in flat/steep base, inexpensive injection molded plastic frames when any stress is placed at the edges of the frame (like when you open them :hammer:).

As the others said- matching base and touching up the horizontal edges will help but some need stiffer lens materials to really stay in the bezel imo.

[Fezz]

This thread may help as well!


http://www.optiboard.com/forums/show...ight=rectangle

[MarcE]

Harry C is right, based on my experience.

Frames with small B and wide A will be edged too long and a bit to short by the edger. I really don't think it's the trace. It may be the tracer programming, but not a stretched or squished frame.

Couple this with lens BC that are too flat on the newer frames. And further compound the issue with thin lenses - and you have a problem.

Do this:
Add 0.05mm to the "B" measurement on the trace/edge
Take down the nasal and temporal edge of the lenses just a bit.
Roll the frame forward with pliers or heat.
Put more BC on the frame.
Squish the frame to make the "B" smaller.

If your tracer can do the first recommendation, then you probably won't have to do the rest. Many times, I have to do all of the above. It takes time, but my lenses fit like the others around the area do not.

[HarryChiling]

It takes time, but my lenses fit like the others around the area do not.

Yeah I have enjoyed looking at the stuff people around here dispense too. It's easy to make money in an unlicensed state if your good at making glasses.

[Barry Santini]

After looking at the old thread sited, I have to agree with Allen from Ice Tech.

Although many of you correctly cited contibuting factors to the problem initially discussed, the main problem is that it's really the edger & the tracer technology we currently have.

Contributing factors:

1. CR 39 lens materials
2. Too thin lenses
3. Minus Cyl axis around 90 degrees
4. Non-conforming eyewire contour
5. bevel apex placement

But, the fact is that wheeled, 3 axis edgers, and non-wrap tracers typically create lenses with a shape *difference* that is greater than the frame or pattern actually is. Another way of saying this is, like Laurie says, that all rectangu;ler shapes, especially with sharp corners, that possess a significant A-B difference, will have their A dimersions longer/larger than they should be.

I routinely "reduce" the "A" dimension of most of these type of shapes during the tracing process. I use the "shape modification" mode that is available for nylor and rimless shapes. For most shapes, they'll need a reduction in the "A" dimension of 0.4 to 0.6mm (yes, that's 4/10ths to 6/10ths!). To compensate for the now *narrowed* frame "PD", we'll increase the DBL by the same amount that I reduced the "A" dimension.
This leaves the effective frame PD the same as the original frame, as least as far as the tracer/blocker frame PD calculation is concerned.

Then, and most important, you must set the edger size 0.4 to 0.6mm higher than a "zero" set size. Otherwise, the lens will be small with the "A" dimension adjusted as above.

The newer "wrap" tracers surmount this problem altogether, for the most part.

FWIW

Barry

[HarryChiling]

Nice post Barry. I have foudn that with tracers if you trace one lens (usually the right) and lay the frame so that the bevel of that traced lens lies along the tracers plane you get a more accurate trace. No tweaks to the shape or anything. Your right about the edgers though the bevel plane in a wrap should not be parralel with the optical axis, this was an issue with the first drill edgers and now they place the drill perpendicula rot the front curve plane, this allows for better lens frame interaction. Since frames in most cases are produced from flat sheets of acetate (or other plastic) then bent to corform to the wrap shape the bevel of a frame goes from parralel nasal and temporal sides to the planes that cross and form an angle, this angle should be mimiced to get the best results, but as long as the back edge of the bevel is removed or made equal to or greater than the angle of the frame bevels then the lenses seat properly. It's nice that the large labs have automated this process, but it can be done more than adequately by hand on a hand stone, I should say as long as it's worth it.

[LilKim]

Also helps to "squeeze" both sides of the frame a little when tracing, to minimize the A and give that little extra to the B.

[MarcE]

I routinely "reduce" the "A" dimension of most of these type of shapes during the tracing process. I use the "shape modification" mode that is available for nylor and rimless shapes. For most shapes, they'll need a reduction in the "A" dimension of 0.4 to 0.6mm (yes, that's 4/10ths to 6/10ths!). To compensate for the now *narrowed* frame "PD", we'll increase the DBL by the same amount that I reduced the "A" dimension.
This leaves the effective frame PD the same as the original frame, as least as far as the tracer/blocker frame PD calculation is concerned.

Then, and most important, you must set the edger size 0.4 to 0.6mm higher than a "zero" set size. Otherwise, the lens will be small with the "A" dimension adjusted as above.

Barry

Barry,
Is it the same effect to increase the B by 0.5mm and then take the size down in the edger? That way I don't have to compensate for the PD. Also, if I forget to decrease the dimension in the edger, I'm still OK, just a bit big. With your scenario, if I forget to increase the size - oops!

I also find that the "error" is lessened when I do what Harry C said and trace one eye but keep is flatter.

[MarcE]

Yeah I have enjoyed looking at the stuff people around here dispense too.

Bad thing is, most of that crap comes from the wholesale labs. Guys that should know how to fit a lens lots better than I.

But I guess if I worked at a wholesale lab, I would be fired because I can only do 8 jobs per hour (from pulling lenses to Clean, Case and Call)

[Barry Santini]

Since frames in most cases are produced from flat sheets of acetate (or other plastic) then bent to corform to the wrap shape the bevel of a frame goes from parralel nasal and temporal sides to the planes that cross and form an angle, this angle should be mimiced to get the best results, but as long as the back edge of the bevel is removed or made equal to or greater than the angle of the frame bevels then the lenses seat properly. It's nice that the large labs have automated this process, but it can be done more than adequately by hand on a hand stone, I should say as long as it's worth it.

FWIW, I rountinely use my new Santinelli LEX 1000's "high-curve" mode for non-high curve work. With it's bevel-height adjustment, I can create the necessary "step-down" to smoothly accomplish what you and I do with a hand stone.

The net effect is the zyl frames have much-reduced "splay" to their temple alignment when you pay attention to proper frame-lens-bevel relationships. Therefore, they also "appear" to stretch out less.

FWIW

Barry

[Barry Santini]

Barry,
Is it the same effect to increase the B by 0.5mm and then take the size down in the edger? That way I don't have to compensate for the PD. Also, if I forget to decrease the dimension in the edger, I'm still OK, just a bit big. With your scenario, if I forget to increase the size - oops!

I also find that the "error" is lessened when I do what Harry C said and trace one eye but keep is flatter.

I think you're right, MarcE. You're system has a better, built-in save guard, as described.

Barry

[Bill West]

Harry C is right, based on my experience.

Frames with small B and wide A will be edged too long and a bit to short by the edger. I really don't think it's the trace. It may be the tracer programming, but not a stretched or squished frame.

Couple this with lens BC that are too flat on the newer frames. And further compound the issue with thin lenses - and you have a problem.

Do this:
Add 0.05mm to the "B" measurement on the trace/edge
Take down the nasal and temporal edge of the lenses just a bit.
Roll the frame forward with pliers or heat.
Put more BC on the frame.
Squish the frame to make the "B" smaller.

If your tracer can do the first recommendation, then you probably won't have to do the rest. Many times, I have to do all of the above. It takes time, but my lenses fit like the others around the area do not.

Well said and exactly right.:cheers:

[HarryChiling]

FWIW, I rountinely use my new Santinelli LEX 1000's "high-curve" mode for non-high curve work. With it's bevel-height adjustment, I can create the necessary "step-down" to smoothly accomplish what you and I do with a hand stone.

The net effect is the zyl frames have much-reduced "splay" to their temple alignment when you pay attention to proper frame-lens-bevel relationships. Therefore, they also "appear" to stretch out less.

FWIW

Barry

I didn't know the santinelli could do that, that's why I said as long as it's worth it with the hand stone statement, technology is always going to try and replace the skills. It will get to a point that the premium charged for wrap eyewear doesn't justify the cost involved to spend more labor on the job in which case you either press the button on your machine or make sure your lab can for you.

[CLANDGH]

I see a lot of people on here with some very good suggestions. I'm a Master Optician, been doing this for 36 years. The best ways I've found to prevent lenses flexing out of the upper and lower eyewire on rectangles is:

1. If the demo lenses fit well, use the same base curve, this is also a good rule of thumb when working on jobs that will have a clip-on, especially the magnetic kind.
2. Like others on here have said, increase the "B" slightly and decrease the "A" a couple of tenths. Too much horizontal width pushes the lens out, and makes thin lenses bow in addition to pulling the frame eyewire back.
3. A flat base curve will stay mounted in them better
4. If installing a "+" lens in them, don't follow the base curve when edging, edge the lenses to the front on the nasal and strap, and to the back on top and bottom, in otherwords, keep the bevel as close to a square straight line as possible.
5. Don't polish the edges. If you do they will slip out more, if you need to polish for the patient, tape the len surfaces, and hand polish only the flat thick areas that will be exposed, the V bevel doesn't show, and doesn't need to be polished.
6. Keep your bevel extra sharp and steep, otherwise the lens thickness behind the bevel will lift the eyewire; A soft point bevel edge will allow the frame to roll right off of the lens bevel.
7. Keep your edger wheels sharp, as the finish wheel wears, the bevel will be too shallow (close to the lens) and be too rounded.
8. On a thin centered Rx, consider ordering it a little thicker so it doesn't bend as easy from the horizontal frame tension.

[gmanlook]

I agree...the lens is a different shape than the frame. Most tracers do not take into account the vault factor (especially on 8 base frames) the distance the stylus travels vertically not just horizontaly...sometimes I cheat by adding .2 to my B and take away .2 from the A (If you have that capability). Also try to get a base curve that is the same as the demo...a lot of times people will try to stuff the wrong base lens into a wrap frame...Hope this helps and good luck...Gary