surfacing transitions

[beth]

Our in house lab has had some trouble surfacing transitions (gen4) recently. Waves and rings are coming out on the lenses. We have always had problems surfacing low power transitions and try to go slow with those but this is on all powers sv and ft's.
Temeratures have been checked on the alloy and polish.
No problems with any of our other lenses.
Any suggestions?

[Jim Schafer]

Hello Beth,
Did you receive the email and attachment on surfacing lenses (Europe Edition) I sent you?

In North America we prefer that you call your lens manufacturing technical support group for process parameters. They are the experts and are familar with equipment in this region.

I hope the information I sent helped you.
regards,
Jim

[Jeff Trail]

Beth,

You say that the temps were checked in the alloy..is that both in the pot as well as the stem? ...you may want to get in the habit of purging the step before blocking because it will get slightly warmer, especially if you have the stem running a little hotter than you should.
I know that I went into an OD's office as a consultant a few months back and they were running the pot at 122 and the stem was running around 126 and they were having the same problems you allude they have a fairly old blocker and if I did get it down to 118 or 119 it tended to freeze up on them because the thermostats and heaters just wavered to much in consistency ... the only way we got it half way corrected (without investing in a new blocker) was instead of using the smaller coburn disposable blocks they had to use the larger blocks.. the heat distortion ring was still there but pushed out far enough it cut away in the vast majority of frames and was far enough out if it didn't it did not effect the lens and patient use.
EVERY time you see that ringed distortion on a lens its HEAT .. The "waves" can be caused by heat as well or the only other thing that maybe doing it is the laps maybe needing recut and running to high pressure on the cylinder machines...99 times out of a 100 though it's the blocker that is the culprit with the description of the problem you are describing... Don't feel to bad I see this problem come up again and again in in-house labs I get called into to check..this and for some reason people seem to have a hard time running spectralite...go figure :-)

Jeff