Rimless disaster

[idoctor]

I have a patient who has brought back the same frame 3 times. It is a rimless frame with polycarb lenses. Everytime the lab puts the lenses in the frame they crack at the screw holes. The lenses are not falling out and the cracks are not interfering with the vision but the patient is irate. I noticed that there is no plastic buffering the poly from the screws. The frame is already 3 years old and we have done a free re-do twice already. Now he is back with the same problem.

- Why is it cracking? Any way to prevent this?
-Any suggestions for trouble free rimless? I like rimless from a fashion point of view but we have to pay an extra $15 to the lab to do the drilling and then we have to deal with these types of issues. I heard that there was some kind of "snap in place" rimless that avoids these charges. Alternatively, we often sell T2 rimless which do not use screws (the bolts are melted into place).
-any suggestions as to nice rimless fashionable frames that are sturdy?

[culland]

If you look back into the OptiBoard posts (07/16) there is a reference from ForLife about the OMS Edgit product that is used to prevent stress fractures around the holes of drilled rimless lenses. Here is the link. (Or else use the search feature and type drilled.)

http://www.optiboard.com/forums/show...hlight=drilled

I've personally always had better luck with the plastic compression fitting type mountings than the nut and bolt type. Just due to over tightening of the nut. We mainly use Silhouette.

[AWTECH]

How to drill poly

It's Poly and the lens was injected under a great deal of stress. When you drill you give the poly a chance to relieve the stress. Unless the drilling is adding significant stress to the situation. Any material must be drilled correctly. Speed the drill used force used when drilling, depth of each drill stroke, clearing the chips from drilling so the whole is not being stressed during drilling.

A sealant that will seal the surface of the poly and then be protected by a thin nylon sleeve will work, if the hole is properly drilled and the lens is a poly produced without excessive internal stress. All poly lenses are not the same. There are products on the market to seal the drilled holes.

There are better materials for rimless than poly if you are not set up to properly drill and install the poly.

[OPTIDONN]

You should see if your lab has resolution plycarbonate lenses or trives, even 1.66 will all work without the lens cracking. Our lab, and I have heard many others, have stoped thier warranty on regular poly lenses. They were losing money on all of the warranty work they had to do. I don't know for sure if it is just a matter of the lenses being processed wrong or if its just the materials. OLA and VCA are working on a set of standards for rimless eyewear. I wonder if these certain standards are practiced by this field if we will see a decrease in lens spoilage.

[OPTIDONN]

Optima's resolution poly lenses are made under much, much less preasure. They say that they will gaurantee that thier lenses will not split and we have not had one come back yet that has cracked. AWTECH really nailed the fact that you need correct drilling speed. We found that out the hard way.

It's Poly and the lens was injected under a great deal of stress. When you drill you give the poly a chance to relieve the stress. Unless the drilling is adding significant stress to the situation. Any material must be drilled correctly. Speed the drill used force used when drilling, depth of each drill stroke, clearing the chips from drilling so the whole is not being stressed during drilling.

A sealant that will seal the surface of the poly and then be protected by a thin nylon sleeve will work, if the hole is properly drilled and the lens is a poly produced without excessive internal stress. All poly lenses are not the same. There are products on the market to seal the drilled holes.

There are better materials for rimless than poly if you are not set up to properly drill and install the poly.

[rolandclaur]

i've always soon poly cracking a lot more than hi index 1.6, 1.67.. especially on the nut and bolt rimless mountings, rather than the compression T mounts

[SarahMP584]

LOVE the optima resolution. Aspheric...Great. Our office uses Airlock the most. However, we do carry the REM Jones New York and Lauren hutton rimless, Which are also compression type mountings, but the actual frame isnt as sturdy. I have broken TWO upon dispensing, trying to put a little Pano tilt on them....Even with my handy dandy three piece mount pliers. I have had little to no trouble with the airlocks though. Great product.

[Chris Ryser]

I have a patient who has brought back the same frame 3 times. It is a rimless frame with polycarb lenses. Everytime the lab puts the lenses in the frame they crack at the screw holes. ..................................

- Why is it cracking? Any way to prevent this?

I have explained this before.

Polycarbonate when drilled heats up during the process and develops microscopic cracks in the drilled surface. The stress when opening and closing the temples as well as having a tight firring adjustment will cause these minute crack to start crazing. Eventually you will have large cracks and the lens falls apart from the drill holes outwards.

I have come up with an easy solution, and the labs or opticians using it report no more cracking problems.

We call it "DRILLSEAL". Comes in a 30ml bottle with a glass dropper. After drilling you put a drop of the solution into the hole, take a tiny scre driver or a tooth pick and disperse the liquid into the hole. It will dry within a minute or two. This product has now dissolved and sealed the microscopic cracks created by the drilling operation. You will never again have cracking and crazing due to the drill holes, when using this technique.

See it at http://optochemicals.com/products/info_drillseal.htm.

[Lewy]

Also ask what your client is cleaning the lenses with as most methanol based cleaners will have a detrimental effect on Poly. I have now stopped using Poly, even Airwear which Essilor says is superior exactly because of this problem. Even the lady I spoke to at Essilor said that Styli (n=1.67) gives less problems.

Lewy

[Chris Ryser]

Not methanol..........................

Also ask what your client is cleaning the lenses with as most methanol based cleaners will have a detrimental effect on Poly.
Lewy

Sorry, have to correct you.

95% percent of lens cleaners on the market do contain ISP (Isopropyl alcohol) and NOT methanol. 30% ISP to 70% water is the standard formula.

It is better to find a surfactant based lens cleaner, might be a bit more expensive, but no damage can be done with those products to any lens on the market including AR coated lenses.

[DaveD]

problem easily solved

Trivex, Trivex, oh did I mention trivex.

[Chris Ryser]

Change cars?........................

Trivex, Trivex, oh did I mention trivex.

Trivex is OK...................................

But you did NOT solve the problem on Polycarbonate.

I a tire on your car creates a vibration do you change cars ???????????????

[Pete Hanlin]

You should see if your lab has resolution plycarbonate lenses or trives, even 1.66 will all work without the lens cracking. Our lab, and I have heard many others, have stoped thier warranty on regular poly lenses. They were losing money on all of the warranty work they had to do. I don't know for sure if it is just a matter of the lenses being processed wrong or if its just the materials.
Internal stress does play a role in lens splitting. However, most problems like this are created by the processing techniques employed.

Regarding drill speed, with polycarbonate lower drill speeds should be used. This avoids the overheating of the material and the microcracks to which Chris alluded. Also, there should be bushings in any mounting that involves metal screws and a polycarbonate (or any other) lens.

Also, the importance of the hole size cannot be over-emphasized. The hole should be just large enough for the screw to penetrate the lens without exerting any pressure on the sides of the hole. If the hole is too large, the screw will create pressure points every time the frame is flexed. Also, any job that has "wobble" will eventually fail. Torquing down the mountings to remove the wobble just exacerbates the problem.

Finally, the holes should be chamfered. On "repeat cracking" jobs, I almost always find that chamfering has not been done. The cracking in poly is caused by the scratch coating, which is brittle and creates tiny fissures when drilled. Without chamfering, these crack propogation points extend down into the substrate and result in lens failure. Pierre Mermet-Marechal (president of MinimaUSA) has an EXCELLENT presentation on drilling techniques.

Processed correctly, cracking should not be an issue with any polycarbonate lens- period. As testament to that, I would offer that I've worn CR-39 in my drill mount sunglasses for over two years now. I abuse this pair horribly- sitting on them, jamming them in the visor of my car, etc.- but the lenses are in perfect condition (except for the scratches on the mirror coating).

[For-Life]

Culland has mentioned it, Chris has mentioned it, and I will mention it.

OMS Edgit!


We had tons of poly cracking until we used this and now we have not had one single little itsy bitsy, tiny whiny crack in any of them.

Use it and love it.


Just a drop of the solution in the holes will do the job. No need to go use a more expensive lens.

[Pete Hanlin]

Where can this product be ordered? I believe our consumables R&D team has looked at this product (we test products to recommend for use in our laboratory network), but on the chance that they have not, I would like to order some and forward it to our R&D laboratory.