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Thread: Coburn 108 Generator Help

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    OptiBoard Apprentice gconn77's Avatar
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    Coburn 108 Generator Help

    Hey folks,

    I was wondering if anyone has any information on the 108 generator. The 108 I use now at my new company is set up totally different than my old 108 at Lenscrafters. The process in calculating the thickness is different. The generator is also different in itself. To set the thickness on my old generator I had this lever that moved the stock... the 108 I am using today has this weird attachment that I place on the stock and over the lens. I then position the wheel and move the stock into the wheel until the tip of that attachment touches the wheel.

    I guess I am just looking for some 101 pointers and hopefully some links to basic instructions of how to use the 108 generator.

    There are some weird things I am instructed to do and do not completely understand why I have to do these things... also when I ask questions, they tell me that they don't know why things have to be done this way... they say that is how we were taught many years ago and we just know it works.

    So I am not a button pusher... I need to know the reasons why. So I need to know everything about the 108 generator and the different configurations of this model... and searching the internet has little results other than a few people that are advertising theirs for sale. Thank you so much for any and all that can help me out a little.

    Best Regards,
    Garry

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    108

    Is it a true 108 or is it a 108 CT? Sounds to me it is a 108 which from what i remember we had a ball tool that you would place in between the lens and the wheel then lock it in and cut the lens down to whatever thickness desired by using the base curve on the dial.Also,where do you work now? I myself work for LensCrafters right now.

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    OptiBoard Apprentice gconn77's Avatar
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    I am not sure which 108 it is... the left side of the thickness dial has a zero hash mark and the right side of the thickness dial has all the numbers on it... my old 108 from Lenscrafters had numbers on both sides of the dial... and I didn't have to use this attachment to set the thickness between the lens and the cutting wheel. Work for ECCA now.

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    108

    One more question when your surface information comes up is it set up with your thickness set like say 2.6@6 or is it say 2.6 @0????? If it is say 2.6 @6 then it has got to be a 108 CT with some sort of ECCA equipment refit like LensCrafters does at the equipment center. Why they would do something like that is beyond me. Why not teach your people the correct way the darn machine works not do this like so and we don't know why that's the way we have always done it. Anyway let me know meanwhile I'll see if i can find out how a 1008 is set up.only other one i know of. Maybe we can get some other Optiboarders input . How about it guys any input???

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    Objection! OptiBoard Gold Supporter shanbaum's Avatar
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    It's clearly a 108 or 108B (the difference being, the latter had a motorized sweep and feed).

    It's a "takeoff" generator, which means that rather than setting the thickness at the front curve, you have two other settings to be concerned about: the blank thickness, and the finished thickness (which should include an allowance for fining).

    There's no link between the two sides of the machine; that's why you have to position the tailstock manually, in effect setting the cutter at the back of the blank.

    It's been about 25 years since I've used one of these, so I hestitate to recount the exact steps, as I'd probably get something wrong. But the general principle is, you start with the dial at the blank thickness, and dial downwards with each sweep, stopping at the desired finished thickness.

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    OptiBoard Apprentice gconn77's Avatar
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    Hey there,

    Thanks for the response back. Here is the process I am instructed to do. I will explain this and then ask a few questions:

    Layout lens, tape it, then measure the thickness and note it. Take the job ticket's CT and add 2.4mm to that. Then take that new modified CT and subtract it from the thickness of the lens blank. That number is the number I set the thickness dial at. (i.e. taped lens is 10.0mm. Job ticket 2.0mm plus 2.4mm equal 4.4mm. 10.0mm minus the 4.4mm equal 5.6mm. 5.6 is where I set the thickness take off dial. I would then take the lens down to 0.00 on the dial.) I see exactly what you are saying, which boils down to the same thing... in this example above using the way you mentioned, I would set the dial to 10.0mm and take off 8.0mm which my final sweep the thickness dial would be 2.0mm, which would be 2.0mm CT. (Keeping it simple not including the added thickness for fining and polishing). This all makes sense. HOWEVER:

    Question #1:

    Why do I have to add 2.4mm? Is there something wrong with their generators thickness?

    Question #2: Why do I have to use this attachment to set the thickness? (This small attachment is manually rested on the end of the stock and has the double tipped like metal caliper that lies between the chucked lens and the wheel of the generator. Basically I slide the stock until this thickness attachment hits the very edge of the wheel, and then I lock it in. After that I lift this other little metel piece, which allow me to move the stock in further until it hits the stop. Then thickness is set.) So again, why do I have to go thru all that? Can't I not use this attachment and run a few test lenses until I figure out how much thickness this gadget accounts for?

    Question #3:

    Knowing more about what kind of generator I am using, do you or have you in the past used a different process in generating the lens? Again assuming you are using the same model generator I have.

    Also:
    Quote Originally Posted by shanbaum
    I finally got my hands on a 108CT manual. If you will e-mail your mailing address to me, I'll send it to you. It contains all the instructions you need, I think.
    Do you still have a copy of this manual?

    I appreciate your help.
    Regards,
    Garry




    Quote Originally Posted by shanbaum
    It's clearly a 108 or 108B (the difference being, the latter had a motorized sweep and feed).

    It's a "takeoff" generator, which means that rather than setting the thickness at the front curve, you have two other settings to be concerned about: the blank thickness, and the finished thickness (which should include an allowance for fining).

    There's no link between the two sides of the machine; that's why you have to position the tailstock manually, in effect setting the cutter at the back of the blank.

    It's been about 25 years since I've used one of these, so I hestitate to recount the exact steps, as I'd probably get something wrong. But the general principle is, you start with the dial at the blank thickness, and dial downwards with each sweep, stopping at the desired finished thickness.
    Last edited by gconn77; 02-15-2005 at 07:34 PM.

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    Objection! OptiBoard Gold Supporter shanbaum's Avatar
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    The only reason I can think of for the additional 2.4mm would be a difference between the width of the spacer on the tailstock (the "other little metal piece") and the length of the pin in the fixture you place between the lens and the wheel.

    The reason you have to position the wheel against the back of the lens (which is what you're doing with the fixture with the pin) is that there is no other connection between the left and right sides of the machine, as there is with "center thickness" generators. These have either a mechanical link (like the 108CT) or an electromechanical one (like most other generators).

    The fixture with the pin is used because without it, some part of the lens other than the center might contact the wheel, preventing contact between the center of the lens and the wheel, and we want to reference the thickness at the center of the chuck/block/lens.

    And the reason you can't simply come up with an "offset" number to use for all lenses is that the position of the wheel changes relative to the tailstock at different base and cross curves.

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    OptiBoard Apprentice gconn77's Avatar
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    Quote Originally Posted by shanbaum
    The only reason I can think of for the additional 2.4mm would be a difference between the width of the spacer on the tailstock (the "other little metal piece") and the length of the pin in the fixture you place between the lens and the wheel.
    I believe I understand that. Example of this would be length of the spacer on tail stock is 10.0mm and the length of the pin is 7.6mm. That would be a difference of 2.4mm. So in this example I contact the wheel and center of lens with the thickness fixture and lock that in. After removing the thickness fixture, there should be a 7.6mm space between the center of the lens and the edge of the cutting wheel. Last step is to lift up the little metal spacer piece, move the wheel out of the way and bring the tailstock forward the 10.0mm and then lock the tail stock in. After doing this the wheel would then be 2.4mm into the lens. So, I believe I understand that to be your reason why I have to add 2.4mm. Of course these measurements of the pin and spacer are simply examples... When I get to work I will get the actual measurement on these and do the math and see if it adds up close... and of course there is added thickness for fining and polishing. Now, at this point I have a few more questions:

    Question #1:

    Why take an additional step by "lifting up the spacer" and it the example above bringing the tailstock in an additional 10.0mm. Why not just leave it down and not use the spacer? Or, if you can explain to me what the purpose of the spacer is?

    Question #2:

    How much thickness should be added to lenses to compensate for fining and polishing? Is there a standard rule? I guess before you can accurately answer this question, you would be some facts from me. Such as what kind of pads I use, fining times, and pressures. I will get this information and post it. Also I guess after measuring the spacer and pin I can take that reading from the 2.4mm and that would equal what is allowed for the fining and polishing. At any rate, is there an industry standard in reference to fining and polishing thickness compensation? Again I will post info all the pads, fining times, etc. when I get home from work this evening.

    Regards,
    Garry

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    Objection! OptiBoard Gold Supporter shanbaum's Avatar
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    The length of the pin in the fixture and the width of the spacer should actually be the same, in which case there wouldn't be any "2.4mm" to worry about.

    If, instead of using the fixture, you simply touched the lens to the wheel, you could leave the spacer up. However, you can't always touch the center of the lens to the wheel, as some other spot on the lens may interfere. Hence, the fixture with the pin, and the spacer on the tailstock.

    There's no "standard" for removal in fining, though pad vendors and lens vendors alike make recommendations for various materials. In any case (notwithstanding any recommendations), you have to do a stock removal test for each material you process. That consists of simply generating a lens and measuring the thickness of the lens on the block (most easily done with a blocked lens thickness gauge - but if you don't have one, you can improvise), fining and polishing the lens, and then making the same measurement as before. The reduction in thickness is your fining allowance.

    Since you mentioned you're at ECCA, the fining allowance should be entered into the lab's layout system, which should be configured to allow you to enter the measured blank thickness. You can also include in the fining allowance any difference between the pin and spacer (the 2.4 mm). Then the takeoff shown on your workticket can be used at the generator directly, no arithmetic necessary.

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    I use the same generator at lenscrafters. Here's a pointer for you. When you are cutting plastic lenses, let's say the thickness cut is 2.0@3, I usually cut 2.0@2.50 just because when you fine the lens out it'll take even more material off the lens. I don't know what kind of fining pads you have, or if you do it in a 2 step process like I do. I'll try to make a ascii example of my general to better describe how to control the thickness.


    thickness@set

    2.5@3




    3 2.5
    2.75 2.4
    2.50 2.3
    2.25
    2
    1.75
    1.50
    1.25
    1.00

    If the cut reads 2.5@3 and you use the thickness guage as mentioned above, set the black at 2.5 and read the red. Usually it's a bit over 3 but the fining process will bring it down. Once the lense is polished and you check to see what the thickness of the lense is, I think you are allowed to be .2mm off o the thickness. If anything, use the same lap you used to fine out the lens for 30 seconds or so on the first fine, then on the second fine, set it for about a minute 30 seconds. It usually does the trick. This goes for polycarb lenses.
    Plastic lenses if the cut is 2.5@3, I usually cut 2.5@2.5 so I leave some thickness. Since it is plastic and the fining pads will remove the material, you'll be safe for a 45 second fine, 2min second fine. Usually the thickness is right on the money. As a rule of thumb for progressive lenses, leave a little more because sometimes after you do a first inspection, you'll notice a half diopter of prism which isn't too nice to have. There's a few ways to fix the prism and axis on a progressive/flattop 28/35 lens. If the axis is 70 and you are getting 50 as an example, block the lens at 90 degrees, most of the time it works out great with about 3 degrees off. Depending on the cylinder power of the prescription, you should be within tolerance. Most places allow 7 degrees off, but since the company is extremely strict, on a 0- -50 cyl, im allowed 3 degrees off, the higher the cyl power, the less I am allowed off.

    If this information is a bore or interesting let me know. I'm up for suggestions.


    I'm not sure if you were asking this sort of question but you would turn the wheel away from you and listen for the rotary blade to hit. then sweep away from you first then back, turn on the vacuum and then start your cut.

    Also to give more pointers, if you could provide a link to your generator I'll try to do my best to give more detailed information.

    In my experience, the button pushing generators are the Gerber generators. It may be a snap to do but the maintenance on those would drive one nuts.

    To add, I use the Coburn 108CT generator at work.
    Last edited by slackware; 04-09-2005 at 01:08 AM.

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    OptiBoard Apprentice gconn77's Avatar
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    Thanks for the post slackware,

    I do not use a 108 CT like the one you use. My generator is a take off generator. I simply measure the CT of the lens blank, and take off however much material needed. So, we have a 6 base sv plastic which comes in at 10.0mm. I want my final thickness to be 2.0mm... so I would take off 7.0mm and fining and polishing would take 1.0mm off and final thickness would be at 2.0mm. Its very easy... my only problem I had when I started this thread was the fact that I did not understand why we had to add 2.4mm to our take off calculations. So in order for my thickness to be correct, we add 2.4mm and works fine. I gave up on trying to figure it out.... I am just happy to be able to get thickess dead on to the 10th.

    Store is getting Gerber equip late summer.... Which is fine, worked with this equipment before... but in a way I really will miss the 108.

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    yeah i love the Coburn 108CTthe only thing i hate about it are the prism rings. they can be a pain in the hiney when lining up the prism axis and making sure everything is peach. now only if i can get the wax blocker working correctly for prism i'll be great haha. if you know of any secrets, let me know. :)

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    Manual for Coburn 108 generator.

    Dear Optical Professionals!
    I have a Coburn 108 Generator and I am looking for the manual.
    If some one have it I will not mind paying for it.
    Please help me.
    Thank you
    Manny

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    I've got a manual I can photocopy or scan. e-mail me: mike@auralens.net

    It is from the ancient Coburn "manuals" book that's about 5" thick and has about every machine in it up to about 1975.

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    Mr Mike please send me at the email address of theoptical1@gmail.com
    and please tell me what is the price first if you don't mind.
    bec time and effort is money..
    please and thank you
    manny

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    No charge, happy to help out.

    I will get it out to you tomorrow.

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    Thank you Mr Mike!
    I do appreciate a lot.
    and please don't mind if i insist to pay bec you are a busy man as well
    please let me know. I will wait for the manual.
    Thank you
    Manny.

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    Best I recall, the spacer was 3 turns to zero take off. Spacer to lens center and diamond, set dial to zero. remove spacer and crank in 2-2.5 complete turn. When you reach zero again, that on 0 take off. then just keep cutting until you get to the desired take off. Check this by measuring the spacer. It should equal three times the # on a complete rotation of the dial.
    Last edited by Speed; 04-01-2013 at 09:32 PM.

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    Manny - they should be in your e-mail right now, it is 4 separate e-mails due to size restrictions on sending e-mails on my end. A total of 29 scanned pages.

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    thank you

    Quote Originally Posted by MikeAurelius View Post
    Manny - they should be in your e-mail right now, it is 4 separate e-mails due to size restrictions on sending e-mails on my end. A total of 29 scanned pages.
    Sir I have only received part 3
    part 1 2 and 4 did not come. please see if you only have to resend .
    thank you very much
    manny

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    Yes, I did get the bouncebacks, I'm resending this morning, PDF pages instead of ZIP files.

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    Hi Mike I was wondering if the pdf with CT108 is available for download anywhere, The machine I have looks like an old coburn model similar enough to ct108..manually operated. If you do have a link to the CT108 manual I would be indebted. email wdeee40@hotmail.com

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    I have used a coburn 113 generator when I used to work for LensCrafters. I just took over a lab and it has a 1008. On my 113 there was a toggle switch for the lens chuck. I can't find a chuck switch on this 1008. Any one out there who could give me some info on this problem would greatly appreciated.

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    Is it perhaps a manual chuck?

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    ¡Hola mike!
    Tengo un generador Coburn 108 y CG-1S y estoy buscando el manual . Si alguien lo tiene no me importaría pagarlo. Por favor, ayúdame. gracias mondra




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