Coburn Lab

[slackware]

Ok this may seem silly but here it goes. I work in a Coburn lab for starters. The wax blocker we have is pretty good but I have a question about prism. Sometimes when blocking everything will look perfect. The axis line is lined up with the 180 degree line and everything is centered. When I cut both the Right and Left lenses, do the surfacing, and I go to check under the lensometer, sometimes the prism is like a half diopter off from the other lens. Is there a way to correct this? I've wanted to experiment but with orders coming in with limited time, I don't want to risk ticking the customer off as well as my lab manager. The power on the sphere and cyl are excellent. If you have any suggestions about fixing the prism to get it to a 1/4 diopter from a 2 down prism or so forth, please let me know.

Also, I sometimes have the same issue with bifocals. I check the axis, power over the seg and make sure everything is within the target zone. I'll dot them up and take both lenses, bifocal to bifocal and check if they are in the same area. They are pretty much on the money with the power and prism. After I edge them though, sometimes I'll get a whole 1/2 diopter difference from the opposite lens. Is there a secret or a trick to correcting prism after it has been generated? Thanks.

[JERRY HUANG]

Lower your wax melting pot temperature a little bit for the summer time and also check your wax over flow...:)

[OPTIDONN]

we had problems like this before. either the wax it a bit too hot and the lens settles more in one section than another. Are you waiting the full five min. or so before generating? the other was that during the chucking process there was some debris stuck in between the block and the chuck causing unwanted prism.

[mooga]

You need to take the troubleshooting step by step from beginning to end. Let's say your 100% positive your surface side machines are all calib. and you follow proper practices before blocking. The things that can cause prism is... 1) Improper wax temperature. If the wax is too hot your cooling time might be too short, also the lens tends to slip a little when you pop the lens out of the ring. 2) Improper lens holding technique. Remember this rule, always use more than one finger(with the exception being progressives of course) when blocking the lens with slight pressure. 3) Improper stem height. If the stem is not letting the block sit flush you will get uneven wax volume. 4)Make sure the ring is always moist on the inside of the well. You want the blocked lens to plop right out of the ring without any force. 4) Improper cooling off time. Wait the five minutes! 5) Improper generating technique. A half off every every five second sweep and don't forget to clean the chuck, rings and while your at it check area around the block where the ring sits. Sometimes wax residue builds up there after time or improper cleaning. Another problem could be a warped chilling ring(especially if it is alum.) or the plate it sits on. Change those at least once a year. Goodluck!

[DPalmer]

I have a question for all of you are you all waiting 5:00 min. before you even generate the lenses ..... seriously??????For those of you who are do you work for LC or somewhere else???

[RT]

Lucky you. The best way to prove to your boss that you're a great surface room tech is to debug a "prism" problem. The first thing to determine is whether you're experiencing a PRISM problem, or a DECENTRATION problem. They're not the same (you can have prism on a plano lens, but can't have decenteration, for example), and they have very different causes and solutions. But you're going to have to run tests. You cannot debug your surface room with the lensometer alone.

The fact that the problem is intermittent suggests that either you a) occasionally completely blow the alignment of the lens, or that the lens is b) sticking in the ring as it is ejected. Those are the most likely causes of a) decentration and b) prism. Another common cause of prism when using a Step One blocker is pushing the FILL button up and down. Tests have shown that only a steady activation of the FILL button yields prism free blocking--pressing, releasing, pressing, releasing, etc. is guaranteed to cause prism. Either way, the intermittency suggests either the lens is sticking in the ring, as others have suggested, or poor blocking technique.

GerCo includes a flat calibration piece with the system--you should be able to block that and not measure any height difference all the way around using a good pair of calipers. If you can, you've got prism. Otherwise, you may need to look for sources of decentration.

The LC 5 minute waiting period could also factor into things here--if the FreeBond isn't completely set up when you generate, all bets are off. Labs that are not under a one-hour constraint generally allow 15 mintues of setup time.

Good luck!

[slackware]

Lucky you. The best way to prove to your boss that you're a great surface room tech is to debug a "prism" problem. The first thing to determine is whether you're experiencing a PRISM problem, or a DECENTRATION problem. They're not the same (you can have prism on a plano lens, but can't have decenteration, for example), and they have very different causes and solutions. But you're going to have to run tests. You cannot debug your surface room with the lensometer alone.

The fact that the problem is intermittent suggests that either you a) occasionally completely blow the alignment of the lens, or that the lens is b) sticking in the ring as it is ejected. Those are the most likely causes of a) decentration and b) prism. Another common cause of prism when using a Step One blocker is pushing the FILL button up and down. Tests have shown that only a steady activation of the FILL button yields prism free blocking--pressing, releasing, pressing, releasing, etc. is guaranteed to cause prism. Either way, the intermittency suggests either the lens is sticking in the ring, as others have suggested, or poor blocking technique.

GerCo includes a flat calibration piece with the system--you should be able to block that and not measure any height difference all the way around using a good pair of calipers. If you can, you've got prism. Otherwise, you may need to look for sources of decentration.

The LC 5 minute waiting period could also factor into things here--if the FreeBond isn't completely set up when you generate, all bets are off. Labs that are not under a one-hour constraint generally allow 15 mintues of setup time.

Good luck!

most of the time i great great prism on progressive/bifocal lenses. the way i block it on the wax blocker is by pressing the cross depending where the prism axis is located on the lense. i do whatever i did to the left as i did to the right. maybe it's the pressure im using on my index finger while pushing the lens. sometimes i see a little wax flow from the lense. sometimes it isn't bad but when i see incredible amounts flowing i deblock and try again. usually when i get a progressive/bifocal order, i try to spend 2hrs with it just incase things go wrong. i usually have a half hour to a hour to spare if it comes out great. it's odd though, maybe it's the generator not aligned in the same spot as the other lens. sometimes when the whole surfacing is done and i get a sizeable diopter of prism, i'll block it up again but i move the lens up a bit and take my chances on getting the quarter diopter which is legal in this state. other than that, maybe once a week i'll get that problem. when im generating, i make sure the chuck is cleaned like a french maid hit it. sometimes i squirt some wd40 in there just so it's not moveable beyond belief. but yeah i appreciate more comments and suggestions. :)

[leonardoptical]

EE

most of the time i great great prism on progressive/bifocal lenses. the way i block it on the wax blocker is by pressing the cross depending where the prism axis is located on the lense. i do whatever i did to the left as i did to the right. maybe it's the pressure im using on my index finger while pushing the lens. sometimes i see a little wax flow from the lense. sometimes it isn't bad but when i see incredible amounts flowing i deblock and try again. usually when i get a progressive/bifocal order, i try to spend 2hrs with it just incase things go wrong. i usually have a half hour to a hour to spare if it comes out great. it's odd though, maybe it's the generator not aligned in the same spot as the other lens. sometimes when the whole surfacing is done and i get a sizeable diopter of prism, i'll block it up again but i move the lens up a bit and take my chances on getting the quarter diopter which is legal in this state. other than that, maybe once a week i'll get that problem. when im generating, i make sure the chuck is cleaned like a french maid hit it. sometimes i squirt some wd40 in there just so it's not moveable beyond belief. but yeah i appreciate more comments and suggestions. :)

Mabye the ultimate solution is blocking the way Super Systems blocks their pre-blocked lenses for the Fastgrind. Never....ever any unwanted prism. Don't know what the stuff is that Don and John have gotten a hold of, but it sure is fantastic. Have no idea if anyone ever tried to grind it up and reuse it, but I would be most interested in anyone who has knowledge of what the "gook" is that Super Systems uses.

If Don or John reads this, you guys have a real winner here. Maybe you should "package" it and sell it to labs. Sure would make a lot of people less frustrated then they are when they have to use either Freebond or alloy.

Super prosperous and healthy 2006.


Dick