Edger and 1.67/AR

[Cowboy]

Hello All,

I am having a slight problem with my edger (Horizon III) cutting high index 1.67 with AR. The problem: When I cut these lenses, I always end up with indentations from the block, and the AR 'cracks', and finally, the lens spins. What I have done to try to prevent this: Lowered the pressure of chuck to 40psi, taped both surfaces, replaced chuck mount with "new and improved," slowed rotation speed and feed speed, and I replace the blade prior to edging. My results: The lens still spins, I still get indentation marks and AR still cracks. I can't imagine going below 40psi to stop indentations, as spin will increase, but may stop ar from cracking.

Has anyone experienced this or can anyone lend some advice as to how I can eliminate this problem (besides replacing edger for you non-Horizon users). I really like the Seiko 1.67/AR lens, and I have even tried others, but the same situation still occurs.

Thanks for your help

:cheers:

Cowboy

[edKENdance]

Used a horizon III for a couple of years. Never experienced a problem like this one. Sorry I can't help.
We've been experiencing strange problems with finished ar polys on our spartans lately. No clue as to why. This is how wierd lab superstisions get started.
Taped both surfaces?

[Jim Stone]

Santinelli 1-800-644-3343

[For-Life]

Try cutting the lens really big, then cutting it down bit by bit. That is a very strange problem, but it could just be trying to take off too much at once.

[Henry]

As I describe before, the AR coatings currently made by vacuum technology are ceramics, no matter they Crizal AR or Teflon AR, tthey are brittle ceramics. So when you edge the AR coated lenses, you will have high chance to flex the lenses and generate cracks. The way to avoid the cracking is to minimize deformation of lenses as well as to avoid flex the lens.

However, the best solution is to use non-ceramic AR coated lenses, such as Chemalux AR.

[Jim Stone]

I don't know. We almost bought a nonconventional AR unit once. Looking back, I am so glad we didn't. The dealer never gave direct answers. This guy was very flakey in his maners. I think the thing was a heart attack in a box.

[Mikol]

Hey cowboy,

Several things I did that made a difference....if useing metal blocks respect the base curve with flatter blocks. Slow the "feeding" of the lens....the less vibration or torque you put on the lens the better......We now use the Kappa but still run certain jobs on the horizon III. hope this helps.


Mikol
:cheers:

[mrba]

3m pads instead of generic perhaps? Large chuck instead of small half eye chuck. Try that.

I love my Santinellis (I have 2). But they will have turned lenses too, especially high minus poly if you aren't careful.

[Cowboy]

Thanks guys for your responses. I will try some of those and see how it works. I'll keep you posted. If anyone else has suggestions, speak up man!

:cheers:

Cowboy

[Joann Raytar]

We run a Horizon II. We use a large, round pattern for cribbing and put a leap pad on the back surface with the paper still on it to protect it from the block cutting in and to help keep the lens from slipping. They also make various AR guards. Vigor's are called blue chip protectors; I've also heard them called slip stop tape. I believe they are small surface saver circles.

http://www.signetarmorlite.com/lab/a...3m_bluchip.htm

[edKENdance]

Jo, that's the best image I've ever seen attached at these forums. I loved the leap II's. I am aware that 3m couldn't make them anymore because the proprietary adhesive wasn't being manufactured anymore. Seems strange that these problems have only started to rear their heads after the intro of the leap III's.
It's a personal pain in my side because I watch other techs follow every possible precaution and still end up with a crazed lens.
Perhaps I might be a little crazed myself.

[Joann Raytar]

edKENdance,

Aren't we all a little crazed? :hammer:

We get a similar product from our wholesale lab. They look the same except they are clear. I can't remember off hand who the manufacturer is but I believe they are from Vigor but I could be wrong.

[Cowboy]

Jo,

One of my local Lab Reps just introduced me to those today. Haven't tried it yet, do they work well? I do the backside leap pad also. My next trick is to switch to plastic blocks as well.
Thanks for your response.

:cheers:

Cowboy

[Jubilee]

As For-Life has mentioned, instead of "one cutting" the lens take it up... a lot... Like an extra 10mm in diameter. Then take it down a bit at a time. If you have small frames for those 1.67 then the lenses are flexing too much do to the amount of material being taken down in a go...

The other suggestion is having them crib the lens to reduce the diameter and thus edge thickness..

Instead of the 3m Leap III's, I use Inland's version. They have a similar design, and are cheaper too. I haven't had really any issues with them. I also use the DAC version of the blue chips as well.

You mentioned trying a couple of different chucks.. Have you tried using a compression chuck. The main shaft is actually a rubber material so it has a lot of give. It has about a 25mm diameter chuck, so you can't use it for those tiny B frames, but it is a excellent chuck for a/r. We used to have crazing issues galore on the gentex profiles.. even when we double padded.. then after switching to the compression chuck, we have only had 2. And we switched to it about 2 years ago.

Cassandra

[Joann Raytar]

Cowboy said:
Jo,

One of my local Lab Reps just introduced me to those today. Haven't tried it yet, do they work well? I do the backside leap pad also. My next trick is to switch to plastic blocks as well.
Thanks for your response.

:cheers:

Cowboy

For most lenses they work well. High minus lenses, especially poly, still spin if the frames B is less than 26 and you don't start big. The protectors also leave a bit of adhesive residue behind that takes a bit of effort to get off.

We tried the graphite blocks and they actually seem worse than metal as far as doing damage when they spin. That may be a pressure issue; I'm not sure what other folks' experience with the blocks might be.

[Clive Noble]

Hello Cowboy, sorry I don't know much, in fact anything, about Horizon Edgers. I do however know tons about edging 1.6. 1.67 1.71 and 1.74 and (as my dear departed granny always said) "touch wood" there's no slippage or damage today.

I use a 5 yr old Briot Accura, it seemed I was the only customer ever to complain (in the world) about slippage, and I solved the problem myself by reducing the weight of the lens on the wheels.
The settings that Briot give are far too heavy.

I bought a 5 shekel (US$1) hammer with a wooden handle, that was the only extra I didn't buy from the Briot guys.

See the attached picture- you can just about see my thumb bottom Rt-;

I simply give upward pressure holding the metal end of the hammer so the lens is relieved of sitting heavily on the cutting wheel. Yes, it does take a bit longer to edge down, but there's no slippage anymore. and there's never any damage to any lens.

This hammer system has become part of the edging process for EVERY lens that goes through our lab.

I also believe it gives longer life to the wheels, but that's just my opinion.

[Jerry Thornhill]

One thing that wasn't mentioned is have you replaced the chuck or the bearings in the chuck. Theses get worn and can cause the twisting and crazing problem.

Mikol was correct on the block base as it prevents a lot of flexing.

I have just switched to a plastic block with mre base curves and DAC's new pad DV-141, this combination is the best that I have used and I do a lot of 1.67 lenses.

I also run the Horizon lll.

Jerry

[Cowboy]

Thanks for the solutions. I will try some of your techniques and see if they help. Keep you posted.

:cheers:

Cowboy

[eegor]

i have found that when i clean out my edger, and have fresh cold water, the leap pads hold much more firmly.

[LENNY]

DIRECT WATER!!!!!!

[Cowboy]

I have an Optronics dry edger - water suggestions do not apply, thanks anyway.

:cheers:

Cowboy

[Chris Ryser]

Cowboy,

If you expierience the slipping of lenses only on AR coated lenses you might have a problem with the slippery hydrophobic coating which has been applied over the AR coating. If that is the case there are some cures for the problem.

[Cowboy]

Mr. Ryser,

Now that you have peeked my curiosity of possible sollutions, please enlighten my world of absent knowledge for said cure.

:cheers:

Cowboy

[Chris Ryser]

Dear Mr. Cowboy,

OMS was the first company to introduce the water repellent coating in 1988. It was developed because of the suggestion by a lens distributor in Vancouver BC, because apparently salt from the pacific ocean stained AR coated lenses. At the time we worked and developed together with I-Coat in California.

At first we offered the coating material to AR coating companies who all told us that they no interest in anything that was water repellent. After 2 month of NO sales we changed the name yo Hydrophobic and suddenly everyybody jumped on the band wagon.

An AR coated layer consist's of thouisands of microscopic crystals which also have gaps in between them . These gaps would collect the salt as well as the facial grease, cosmetics and so forth.

A hydrophobic coating will fill the gaps between the crystals so that dirt can not penetrate anymore into these gaps without changing the characteristics of the coating. This will make the AR coated lens easier to be cleaned.

So all the claims by different AR lens coaters that on their lenses that a water droplet will ball off at 41 or 30 degrees is a bunch of balyhoo on purely advertising.

In the early times everybody in the retail sold, and still does, the "micro fiber cloth" type lens cleaners because the tended to be the best and finest to wipe part of the dirt out of the gaps on AR coated lenses. This has actually become obsolete when using lenses that have a "hydrophobic or easy clean coat" on top of the AR coating.

Today there are several types of hydrophobic applications. Most of the coating companies now apply a hydrophobic material that is applied under vaccuum during or after the coating process.

the newest types are made with polysilxanes which are very slippery to which nothing adheres properly. "Compare to the treated paper sheets were self sticking postage stamps are stored".

Of course now you do encaounter problems when putting the lenses through your edger. Your sticking pad do not hold the lens properly and slipping occurs. As stated in an above posting, cutting the lens to larger sizes and the reduce it in 2 or 3 steps could help because you apply less pressure on the edgers to remove large amounts of plastic in one shot.

Try to find pads that will overcome the problem of slippery lenses, but I have not seen any on the market yet.

Another solution would be to get the lenses without the hydrophobic coating and you will have no slip problem. You can the apply a hydrophobic treatment easily after having finished finished the lenses just before mounting them into the frame. So0me of these products also include anti-fog and anti stat protection.

[Cowboy]

Dearest Mr. Ryser, my optical genius of lens products;

Thank you for that informative post. I shall take that into consideration. Would you mind forwarding the costs for such a product to my personal e-mail? Thank you again for responding.

:cheers:

Cowboy