Poly Splitting

[MVEYES]

Anyone have any hints on keeping polycarbonate lense from splitting at stress points in metal or rimless (drilled) frames?






Jerry

[soontobeopti]

Unfortunatly Jerry, I cannot answer your question. I am wondering it myself
I was always wondering; I heard that you cannot but a Polycarbonate No Line Progessive in a rimless frame. Something about the make of the lens doesn't support the rimless frame. Is that true??

[varmint]

MVEYES said:
Anyone have any hints on keeping polycarbonate lense from splitting at stress points in metal or rimless (drilled) frames?






Jerry

Use Trivex/Trilogy, no more splitting. I won't sell a drilled lens in any other material. I also rarely see these pt's back for adjustments on drilled rimless with Trivex/Trilogy.

[Cowboy]

Firstly, is there a specific pattern to the splitting, i.e., only in metal frames or rimless, etc. What type of edger are you using? If you are using a diamond roughing wheel on a wet edger, there could be too much pressure being applied on the lens and creating stress throughout the lens, and over a period of time, the combination of frame stress and edging stress is causing the splitting, contact the edger manufacturer and see if there has been other complaints and possible solutions.
How is the sizing of the lens, we all like to think that we have it just right, but sometimes there is just enough stress remaining that splits the lens.
As for Drill Mounts, many factors here. Mostly, what I have noticed, is that, especially with poly, if the bit is dull and/or too high of speed, this will cause over heating and create micro splits that develope into star bursts around the hole later. change your bit after 50 pairs and ensure a controlled smooth entry into the lens on a slower speed. I use a Craftsman dremel with press and use speed 2, I have not had a single problem in over a year.

I have not all the answers, but hopefully the ones provided will be of use to you.:D

Cowboy

[For-Life]

The myth about not being able to do a progressive poly is false. I have done them many and many times. I have heard about Trivex even splitting, not as much as poly, but still splitting.

You want to get OMS Edgit. It is a compound that you drop into the holes. It then seals the little scratches and cracks in the holes and prevents them from splitting. From my understanding, the problem is that we cannot polish the inner holes, and as we know poly is cut dry, but needs to be polished wet. The polishing takes away all of the little cracks; however, we cannot do that in the holes. This is where edgit comes in.

As I said in another thread, I am not associated with OMS at all, I just use their product.

[MVEYES]

Any information on where to acquire OMS Edgit would be appreciated.


:D
Jerry

[rsandr]

Hi Chris, i know ive asked you this before but to refresh my memory,
where do i get OMS in the UK is it Inland?

Rick

[chip anderson]

I just drilled several hundred holes in Lexan (Poly) by hand to put new windows in my camper shell for my pick up (yes, I live in the South and we all have pick-ups) with a hand drill. No cracks. What did I do. Liberal use of oil (highly recommended by most plastic manufacturers) on the drill bit and drill site. Don't know if it was signifcant but I also used titanium coated bits.

Chip

[Pete Hanlin]

Suggestions for drilling poly...

• sharp cutting bits (replace frequently- every 30 lenses or so)
• slow drill speeds (if you have a CNC driller, set for lower speed)
• "bounce" the bit (drill part way down, lift up, further down, lift up)
• CHAMFER (use a tool to give the hole edge a wide bevel- eliminating micro-cracks in the surrounding hard coating)

The two main enemies for poly drilling are heat and microcracks. Research shows that uncoated lenses don't crack (i.e., the rigid hard coating creates the crack propogation points that facilitate lens failure). Several companies have suitable chamfering tools, but a rat-tail file will not work. You want a wide angle bevel around the edge- a narrow tool will merely widen the hole- which will worsen the problem.

This same advice will also work with Trivex- which has some of the properties of a thermoplastic resin.

[rsandr]

Ive started using cobalt drills instead of HSS and am enjoying good results.

Rick

[Jackie L]

Silhouette Optical Labs can provide you with a kit that includes the proper tool (tapered reaming bit) to deburr the drilled holes. This conical file works wonders on poly and does decrease the cracking factor. Others refer to this as a burnishing or chamferring.

[Chris Ryser]

Anyone have any hints on keeping polycarbonate lense from splitting at stress points in metal or rimless (drilled) frames?

soontobeopti Unfortunatly Jerry, I cannot answer your question. I am wondering it myself

rsandr said:
Hi Chris, i know ive asked you this before but to refresh my memory,
where do i get OMS in the UK is it Inland?

Rick

Rick
Yes it is Inland, at least he should have it. If not you can get it from our subsidiary OMS Europe. Full addres on our website on the home page at :

http://optochemicals.com

[Andrew Weiss]

Maybe this is too obvious, but if you're using acetone to clean the lens after marking and drilling, or if you're using an acetone-based screw-lock to keep the mounting secured, the acetone may well be causing the stress fractures.

[Chris Ryser]

Microscopic cracks will occur during drilling and reaming on poly, very often due to the heat developed.

If you seal these cracks with polycarbonate edge polish there will be no more of those cracks that will tend to craze at a later date.

Also acetone and acetone fumes are the enemy no1 of poly and wiinduce crazing of the materieal.

Use a no acetone marking remover only to take off the progressive markings.

[rsandr]

Chris said:

If you seal these cracks with polycarbonate edge polish there will be no more of those cracks that will tend to craze at a later date.

I have a large bottle of this but i dont use it as I reverted to buffing.
Is it damaging to the surface of the lens? Or will it safely wipe off?

Rick

[Chris Ryser]

Rick,

This product will NOT damage the poly. You take a dry tissue get some of the liquide on it and just wipe it over the edge which will instantly become glossy and dry in seconds.

You can also put a drop of it into freshly drilled rimless mount holes and it will instantly seal the microscopic cracks that occurs whiile drilling, therefore preventing later crazing from the screw hole.

[Cowboy]

Chris,

Send me some....you have my info. The smallest supply will be sufficient for now.

:cheers:

Cowboy