Swirls and Finer Marks with Poly

[bill8234]

Hi all-

I apologize for resurrecting this age old issue, but, I'm hoping for some help. We are getting 'swirls' on most of our poly lenses. They are indiscriminate when it comes to power/cyl and is very inconsistent in regards to location/pattern.

• Genterator:2G Turbo with a fine surface finish (spiral sep 0.63 mm.) The curves and axis have been calibrated and re-calibrated. The motor and blade are relatively new.
• Finer and Polisher: Both are Acuity Plus. The finer is using tap water at a fairly consistent 58 F. Polisher is using Plasti-sheen 2020 chilled to 53 F. Polish is changed every 3 or 4 days depending on volume. Machines have been calibrated for axis and center.
• Pads: First fine is a P280 (black) @ 17 psi for 1:30, Second fine is a P1000 (brown) @ 17 psi for 1:45. Polishing is with a pink pad @ 20 psi for 6:00

We've also changed pins and centers in our blocks. All generator marks are being removed in first fine. Im not sure if the first or second fine are causing the issue and they aren't polishing out? We had this same issue 3 or 4 months ago and after changing out a few expensive parts in the finer and polisher it was determined our fining pads were too aggressive and thus the P280 and 1000. This time it seems like it is coming out of nowhere. I should note that the swirls are very very faint but become more visible after backside coating. They don't seem to be showing up in any sort of consistent pattern (as if to indicate and axis or curve issue.) I've run out of ideas here and am hoping for some direction on where to go next. Thanks for your time!

-Bill

[uncut]

"swirls on most......" I think a picture or two of examples would help the members in assisting you. Are you filtering your water, before use?

[bill8234]

"swirls on most......" I think a picture or two of examples would help the members in assisting you. Are you filtering your water, before use?

Something I wish I had done earlier today. I will take some pics and post them when I get in tomorrow morning. We have always used water directly from the tap with no filter. Is this something to consider?

[fjpod]

have you tried a little longer second fine and/or polish time? Maybe try a 7 second test...first fine for the normal time, then draw a six spoke pattern on the concave side of the lens with a sharpie, and run it on a second fine pad for 7 seconds. See if that reveals an uneven pressure pattern. If not, try it again between the second fine and polish.

[camillebnks]

Double up on First fine pads.

[uncut]

Something I wish I had done earlier today. I will take some pics and post them when I get in tomorrow morning. We have always used water directly from the tap with no filter. Is this something to consider?

It sure can help eliminate introduction of contamination due to, watermain flushing, high neighborhood water use, and generally things that can ruin lenses.

[Trip]

lisher is using Plasti-sheen 2020 chilled to 53 F. Polish is changed every 3 or 4 days depending on volume.

_ Do you note any difference when the polish is changed? Less, more, no difference .. ?

[Jubilee]

Are the lenses being cribbed?

How are the optics? Prism/Axis issues?

Have you tried increasing the time of the fines? Going to a lesser abrasive pad might mean needing to bump up the time.

Have you tried something like the 7-10 second test? Seeing if there is an uneven wear, signs that it is fining from the inside out would be an immediate indicator that something is amiss with the curves.. (too flat)

Make sure the water and polish have significant flow, and that all pads are smooth and not wrinkled.

[bill8234]

I have attached some pics of lenses in different stages. This a.m. I decided to ignore my measurements and just steepen the curves on the generator. I also opened up a new bucket of polish and changed that out just to be safe. We still had a few but I think perhaps my sag gauge is malfunctioning? I have tried various 10 second fine tests and they all seem to offer mixed results. I have been shy about increasing fining times very much for the fact that poly seems to build up on the pads. I don't know if that contributes to swirls or not.... Anyhow the problems seem to be improving with the new curves. Power and axis have always been spot on. The following are images I took earlier today, let me know what you think! I wasn't able to get a clear photo of swirls on a polished lens...they are simply too faint, even on a polarized lens.
(Appearing in order pre-fine, post-first fine, post-second fine, and a wet post-second fine)

[bill8234]

_ Do you note any difference when the polish is changed? Less, more, no difference .. ?

No noticeable differences except on occasion. Today after further adjusting curves and changing the polish there was a difference.

[bill8234]

have you tried a little longer second fine and/or polish time? Maybe try a 7 second test...first fine for the normal time, then draw a six spoke pattern on the concave side of the lens with a sharpie, and run it on a second fine pad for 7 seconds. See if that reveals an uneven pressure pattern. If not, try it again between the second fine and polish.

I will have to try your method. I've always gone from the generator straight to second fine for 10 sec. and go from there. A first fine may help to identify smaller errors in curvature?

[Trip]

Morning, ... from the pictures posted it appears you are blocking on optical center, and that your progressives will be decentered on the block ... (I don't know if you see it more on progs vs sv or FT's), but an uneven stroke pattern at the cyl machines would certainly enhance the opportunity for you to find swirls at the end of the process. Also noting from the pictures that there was one or two of the lenses that did not have a pin bevel applied against the edges before fining and polishing ..... doing this consistently is recommended as well.

[OPTICALTROLL]

A lot of good info in here I would try the extra pads or a slightly longer cycle. Its been years since I've surfaced but those are some quick fixes.

[PRECISIONLAB]

Great troubleshooting info. Seems like all variables have been addressed and all curves / axis have been dialed in. I would recheck curves from Generator since the swirls are on the outer portion of the lens which means it might be cutting strong minus. Consider the pad as the culprit. Since you mentioned the swarf build up I'm guessing that during the first part of the cycle the curves are being corrected (outside to in) and smoothed. As the cycle continues, the "grit" is being "exhausted" and all that is left is the paper backer leaving the swirl marks. Ask your local wholesale lab to provide samples of the pads they use. If curves are dialed in Poly first fine shouldn't require more than 1:30 to 2:00 minutes. Try decreasing first fine and increase second fine. We use a one step process with great success. See photos.

[bill8234]

Morning, ... from the pictures posted it appears you are blocking on optical center, and that your progressives will be decentered on the block ... (I don't know if you see it more on progs vs sv or FT's), but an uneven stroke pattern at the cyl machines would certainly enhance the opportunity for you to find swirls at the end of the process. Also noting from the pictures that there was one or two of the lenses that did not have a pin bevel applied against the edges before fining and polishing ..... doing this consistently is recommended as well.

Progressive lenses don't seem to be more of a problem vs. sv and flat tops. It is interesting that you mention uneven stroke pattern. The pattern is centered but it seems a bit skewed. I will have to contact Coburn for clarification on this. It is not more than a mm out of square but perhaps this is the culprit? Unfortunately I am a returning lab manager. The previous manager prevented others from learning about the equipment. I, being the most senior and most knowledgeable available staff member, was handed the job. I'm doing the best with what I remember from 5 or 6 years ago.

[bill8234]

Great troubleshooting info. Seems like all variables have been addressed and all curves / axis have been dialed in. I would recheck curves from Generator since the swirls are on the outer portion of the lens which means it might be cutting strong minus. Consider the pad as the culprit. Since you mentioned the swarf build up I'm guessing that during the first part of the cycle the curves are being corrected (outside to in) and smoothed. As the cycle continues, the "grit" is being "exhausted" and all that is left is the paper backer leaving the swirl marks. Ask your local wholesale lab to provide samples of the pads they use. If curves are dialed in Poly first fine shouldn't require more than 1:30 to 2:00 minutes. Try decreasing first fine and increase second fine. use a one step process with great success. See photos.

Here are the pads after fining....does this seem like an excessive amount?

[PRECISIONLAB]

I don't see any swarf load. I've never been a fan of 2 step fine especially with the brown p1000. I use the DAC Vision Velocity pad for poly one step fine (PDR 6050NC). Ask your supply rep for some samples and see what works for your lab. Based on the photo of Generator cuts, you may not need an aggressive first fine pad. Also, I had issues with some of the laps..flatter curves with a lower tool height. If the lap is thin.. when the lens is chucked the arm is not perpendicular in a sense binding the lens and lap assuming you have the LOH style adapter on your Acuity. I would see swirls on the lower portion of lens similar to your situation. Try by using the lap in the latest picture and run a foam lap with same curves and check results between the two lenses.

[Chris Bowers]

Sounds like your water is too cold. Best practice is to usewater at 65 F. Direct water in Saint Paul is going to be around 56.5 degrees. Useyour water in a recycled container and cool from ambient room temp to 65. Thisis also critical for polish. Add a drop of dish washing soap as a surfactant.This helps keep poly from loading the pad. I also agree you should be able to one step these all day long.