off power problems

**Rich R** · 05-01-2004, 11:14 AM

I'm recently getting some off power problems on surfacing.
I'm wondering if some may be due to us running our finers with direct water from outside instead of a slurry bowl underneath, and since it has been pretty hot the water is a bit warm.
Has any other lab rats experienced this exact problem and what was your solution.
Thanks, Rich R

**rsandr** · 05-01-2004, 03:02 PM

I had problems when we started surfacing.
I increased fining and polishing times and the problem went away.
We one step fine for 2 mins and polish for 5.

**mrba** · 05-01-2004, 03:09 PM

Yes,

temp has gone up here in the sunny state, transitions especially abberating. How is your chiller working?

**rsandr** · 05-01-2004, 04:30 PM

Does it get that warm over there that tap water is warm?
I hope you never visit Englandcestershire, you would have a shock.

**mrba** · 05-02-2004, 05:41 PM

Sure it can get that warm, but when surfacing a few degrees can make the difference. If you have a 20 increase in climate a 5 degree increase in polish can ruin you.

**Pete Hanlin** · 05-03-2004, 11:04 AM

A couple questions...

Are the powers trending in a particular direction (e.g., flat or steep deviation from desired curve)?
Is the problem localized to a particular area of the lens (e.g., over seg lines)?
Is the problem constant or transient?
Has anything been changed in your lab management software recently (new version, new settings, etc.)?
Do you have an arc lamp to inspect the rear surface of the lens?

Thanks,
Pete

**Rich R** · 05-03-2004, 10:20 PM

Hello Pete, I'm getting a little bit of everything, I just got transferred to this lab, seems that I'm getting plus stronger and minus a bit weaker, not all the time.The block centers are wore out, so we're replacing them now, blocker temperature seems ok. Finers as I said are from the main water lines, they get to about 80 degrees when it's very hot outside. Polishers are about 60 to 65 degrees using chiller and cooling coil, however I discovered today when polish runs low in slurry and foams up it got to around 75 degrees.
Would appreciate any input that may help.
Rich R.

**jofelk** · 05-04-2004, 06:07 AM

If you are using one step pads, check program and make sure pad compensation is correct.

**Pete Hanlin** · 05-04-2004, 06:52 AM

The 75 degrees wouldn't be optimal, obviously- but from your description, it sounds like the problem is more related to power than surface quality.

Pad comp could be a factor, but if anything your pad comps would be set too low- since you indicate the back surface is coming out too flat. Regardless, I don't think your current problems are related to pad comp- because you would end up with a lot of work on power with the occasional lens that's off due to wrong tool pick when the system rounded the wrong way. If you are using a Gripper system, that could throw the compensation off as well if you haven't entered that into the system.

What about the surface quality of the tools? Any flat spots, gouges, or incorrect curvatures? Are the tools compensated? With flat curves, if you had non-comp tools running when the LMS has been told they are comped, that could be causing an issue.

I've also seen labs add tools over time and end up with a mixture of compensated and non-compensated tools (or, tools compensated to different pad systems).

If the problem persists, feel free to send some lenses in and I can inspect them under the arc lamp and see if we can narrow down a list of possible causes.

**JRS** · 05-04-2004, 11:11 AM

Pete - can anyone get to the technical pages on the Essilor site?

If they can, you could direct them to the Guideline manuals. I can provide it in Spanish if you need to add it to your list - or to anyone out there who needs a Spanish version. The Guide can assist with these types of problems.

**Pete Hanlin** · 05-04-2004, 04:15 PM

Currently, the only thing accessible on essilorlenses.com without logging in is ELART (in response to requests from OptiBoard). However, any laboratory with an Essilor account number can log on using their account number for the login and password.

RT · 05-04-2004, 06:13 PM

A 15 to 20 degree variation between fining temp and polish temp can cause both surface quality issues, as well as aberrations that will look like a power problem. This problem will be more apparent on thermoplastics such as polycarbonate, and will also be more apparent when blocking on wax. Best bet is to match finer temp and polish temp, which may be difficult on a fresh water system. Temp phenomenon typically doesn't usually affect plus lenses, however, due to the thicker center. In that regard, it sounds more like a pad thickness issue.