polycarb manufactered - how?

[Cowboy]

Ok, so here's the deal.....I was on the phone the other day with my lab and we got on the topic of polycarbonate and ways to reduce cracks with drill mounting - I have my own techniques but wanted to see if they had reoccuring problems and how they were handling them. Then we talked about the Orient and the way they make polycarb - they use a "pounded" technique that creates microscopic cracks and when drilling, it enhances the cracks and therefore there would be no cure for drill mounts with that type of manufacuring. Maybe I am wrong, but I thought, and from what I have learned about Poly, is that it is an injected - moulded material.

Your thoughts.......
:cheers:

Cowboy

[For-Life]

Optiboarder Chris Ryser has a product that stops the cracks. It is a solution that when you drop it into the drilled holes it stops the miniature cracks within the poly.

A couple of years ago I was getting a lot of cracking. I sent a bottle to my lab and have not had one crack since then. Here is the product:

http://optochemicals.com/main-english.htm

[Gary Falk]

Polycarbonate is injection molded. The raw material is in the form of a pellet. It is then heated to a point that it is softened and then pressed into the molds. Modern methods have eliminated much of the internal stress in the lens. If your lab is having this kind of problem with cheap Poly coming out of the Orient, then they need to find a better supplier. Or maybe you should find a better lab!

Here is a link to how to drill poly:http://www.vision-ease.com/product_s...lessMounts.pdf

I have poly lenses in a drilled rimless that are 5 years old and no problems with any cracks. Many of the cracking problems are chemical related also (lock tite).

[Chris Ryser]

If your lab is having this kind of problem with cheap Poly coming out of the Orient, then they need to find a better supplier. Or maybe you should find a better lab!

There is no such thing as cheap poly from the orient. It is all the same material. Besides that even some or most brand name poly is made in the orient.

Polycarbonate is the least expensive material there is to make lenses wether in the USA, Europe, Taiwan, Thailand you name it. .........But it does not break and shatter.

Here are the properties of polycarbonate: http://optochemicals.com/polycarbonate_properties.htm

[hipoptical]

No matter how you drill, there are certain problems with poly that cannot be eliminated. Poly can withstand tremendous force applied on impact. However, if you took a large sheet of it, cut a hole large enough to put both hands through, and grabbed opposite sides of the hole, you could pull it apart if you tried hard enough. POINT: when you drill a small hole and insert a pressure-mount bushing or even a screw, there is generally a lot of pressure within the hole. The cracks are stress induced by mounting. Ryser's goop will prevent the "natural" cracks from appearing, but if you don't mount correctly, the cracks will develop. It's called tensile strength. Poly isn't as good as other materials. That's why there are ADVANCES in TECHNOLOGY: Trivex, 1.67 are both FAR better, Trivex having the highest tensile strength, but 1.67 isn't far behind. Trivex has the advantage being ALSO impact-resistant. Poly is cheap. You get what you pay for. Don't stop using it, it's a good material. Just be careful mounting it.

[Chris Ryser]

Ryser's goop will prevent the "natural" cracks from appearing

As there are NO natural cracks in a polycarbonate lens................the guy's from Essilor and others are going to kill you for saying that.........................

Ryser's goop will seal and fuse the man made cracks which occurred during the drilling operation.....by quite a few reasons...............and then as there are NO MORE cracks they can not progress until you artificially help it along.

:D

[For-Life]

Now all poly is the same, but are there not cleaner techniques with the molding that can improve the visual quality and reduce cracks?

[JERRY HUANG]

Apply Chris's alcohol/aceton proof sealer.

[hipoptical]

As there are NO natural cracks in a polycarbonate lens................the guy's from Essilor and others are going to kill you for saying that.........................

:D

I've already had run-ins with Essilor before. I told them Gentex was trash and would never use it. I said out of all the poly out there, it is the absolute worst. They stopped talking to me for months... (best few months of my life in this business!) We are still on strange terms. They sell to me if I want to buy only because they can't say no. I buy from them pretty much just to irritate them occasionally. :D

[For-Life]

I've already had run-ins with Essilor before. I told them Gentex was trash and would never use it. I said out of all the poly out there, it is the absolute worst. They stopped talking to me for months... (best few months of my life in this business!) We are still on strange terms. They sell to me if I want to buy only because they can't say no. I buy from them pretty much just to irritate them occasionally. :D

Gentex is junk. Airwear Aspheric is much better. I am sure any Essilor rep would tell you that.

[hipoptical]

The Essilor rep tried to argue with me about Gentex. That's where things went awry. Airwear is better- good, actually, but too expensive generally speaking.

[Judy Canty]

Ask your lab about Polycore LiteAir polycarbonate lenses, available in SF & F-SV, FT-28, and Micro PAL. All with either tintable hard coat or MxPlus A/R coating.

**End of shameless plug** :D

[Gary Falk]

There is no such thing as cheap poly from the orient. It is all the same material. Besides that even some or most brand name poly is made in the orient.

Polycarbonate is the least expensive material there is to make lenses wether in the USA, Europe, Taiwan, Thailand you name it. .........But it does not break and shatter.

Here are the properties of polycarbonate: http://optochemicals.com/polycarbonate_properties.htm

While the properties of all poly lenses are the same, there is a difference in quality of the finished lenses.
Some manufacturers use a lower quality of material than others, have lower standards, less precise molds, less scratch resistant coatings, etc. This is how they cut their costs. That is what I mean by "cheap" poly. And yes it can come from any where.
Also, many of the problems come from the labs not processing or drilling the material properly. The most important thing to many of them is just get it done quickly.

[chip anderson]

I seem to be remembering a few lectures where it was stated (as fact?) that poly had a gray appearance and gray flecks (particles in the material) until someone noticed that the then latest generation of CD's were of much higher quality and the industry switched over to CD quality poly. Anyone else have a long memory?


Chip

[fjpod]

I suspect that the sharpness of the drill bit and the force with which it is pushed through the lens has something to do with it. A dull bit will cause a ragged surface, inducing cracks; especially if it is forced through quickly.

Has anyone tried a new bit to see if their problem goes away?

[LENNY]

New bit?

You can change them after you drill out the screw?:drop:

[JRS]

Those grey flecks were carbon particles Chip. And the reason that Poly lenses got cleare was because of the CD industry. The CD industry needed a purer product. We just benefited from it.

[Chris Ryser]

Gentex is junk. Airwear Aspheric is much better. I am sure any Essilor rep would tell you that.

There is a most modern fully automatised lens factory in Rhode Island that turns out thousands of pairs of Polycarbonate lenses a day. They make every type of lenses right up to progressives in different designs.

These lenses are sold without any brand name as a generic lens and supplied to wholesalers, other lens manufacturing companies like J &J and many others who then resell them under their own brands.

Company was privately started and then sold few years ago to SOLA which is now part of the Zeiss Empire. So I could assume that Zeiss is now also selling generic lenses under their own name.

[Chris Ryser]

Apply Chris's alcohol/aceton proof sealer.

Jerry..................I hope you mean that the product does not contain alcohol/acetone ......................which it does not.

These product can totally destroy poly. Years ago I used methanol to remove a sticker on a motorcycle windshield, next morning the windshield had thousands of cracks over the whole surface

[fjpod]

New bit?

You can change them after you drill out the screw?:drop:

I thought we were talking about drilling poly lenses, not drilling out screws?? I would never use the same bit for both of these purposes