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I have a coburn 506 that’s been in the lab for years and it’s always worked however, recently it’s began to give us nothing but issues when doing poly lenses. We have checked every possible cause and we can’t see to locate It.
The problem we are having are finer marks. They don’t fine out and won’t polish out. Sometimes they don’t show up until the lens is coated.
Help!
-jonathan
You will need to check your stroke and orbit first. I haven't touched these in years, so I can't tell you what they should be. Fining, I think, is 26mm orbit and polishing around 30. Your pin pressure should be 18psi.Quote:
Originally Posted by riverviewjonathan
If the pads are tearing off, your axis is off. You should check those, too
Try a more abrasive fining pad or adjusting your times and pressure like lensmanmd suggested.
Also look into how old your polish is. Old polish makes for a sloppy final product.
I feel your pain though- when the coater makes defects evident my heart sinks!
i was having similar issues with fining marks on my finished lens, mostly Transitions lens in my case. we had a Gerber Tech in the lab one day and he suggested this upgrade that wasnt Gerber related so we checked it out. and to our surprise kinda easy to install. We upgraded 1 set of our 506's with otleys. we have enjoyed them and the machine isnt as loud when running as it used to be. Pro:you dont have to get in the floor and grease the machine anymore.. you still have to grease the top side though. Con: you have to go the extra mile to seal the baffles from polish or water getting to the machine.(rust) it did help with the fining and took out the side to side play. heres the link to what we put into our machines. good luck.
http://www.inlanddiamond.com/optical...s-and-parts-2/
I appreciate all the info, we have messed with and fixed the slight issue with the orbit(it was off by millimeters) so the finer marks are closer to the outside. They are still there but not as bad. They only appear after the second fine. We had just recently converted the 506 to use fresh water instead of recirculating in the bowl thinking that would solve the issue but the advice we got from a coburn tech to use cool water seems to be detrimental because it’s causing material to cake on the pads which may be the problem now. Our technician we have said that the cold water is the issue.
Material caking on the pads have nothing to do with water temps. This would be a relationship to water flow and/or the grit of the fining pads. You mentioned fixing the Orbit, but what about centering the pattern? Also, have you checked the regulator? The PSI on the regulator may not be accurate. How much stock removal are you expecting? Are you using the correct pads per material?Quote:
Originally Posted by riverviewjonathan
Update. Forgot to ask this question. Your generator calibration. Kicking myself for not asking. There are three basic points of view. Outside in fining, inside out fining, and straight on fining.
Outside in means that the generator is calibrated slightly strong. Inside out is slightly weak. Straight on is per mfr recommendation. Prior to converting to FF/STP, we opted for outside in to minimize waves at the oc. This is the most preferred method.
The pattern we made sure was centered when we did the orbit. The regulator we have not checked, the pressure we have set is between 18 and 20psi. We are using the correct pads per material. It’s good to know temp doesn’t matter. The coburn guy was making sense saying that it’ll help prevent any aberrations from the heat caused by friction from the lens and pad.
The water flow is the same we’ve been using since before this issue appeared. When it comes to the generator we have steepened and flattened it trying to get the best fine possible and as far as the calibration it seems to be calibrated but maybe there’s something we are missing. We are using an national optronics 2G. We use PSI dispablocks to block our lenses with alloy.