myodisks

[hawaiioptician]

hello,

recently switched from a dispensing optician, to a surfacing one. I am of late, obsessed with myodisks. unfortunately, my SGX machine can only cut a max 20 curve, AND i keep miscalculating center thickness and cutting through the blank trying to cut the front curve. any advice in general?

and specifically, where can i get some thick @ss blanks to grind some crazy high lenses? It seems i keep running out of space with my standard blanks.

one other one. If i cut a 10 cyl on the back at a 180, and a 10 cyl on the front at 90, id have a -20 sphere, no?

thanks guys.

[MikeAurelius]

X-Cel optical has lens blanks up to about 20 mm thick, and can also custom cast lenses for you (example: +6 front +6 back with a 20 mm edge).

If you are having trouble with calculations, what I've done in similar cases is to get some graph paper and a compass and actually draw out the curve design on paper. If you draw to scale, you can direct measure the thicknesses and locations you need.

If you try something like that with crossed cylinders on the front and back, you are essentially making an isiekonic lens, and really screwing around with magnification in the various axis. With that high of a cylinder power, you would have to get your axis aligned PERFECTLY, otherwise the powers are going to go nuts on you.

If you are doing a lot of myodiscs, I'd suggest you lay in a stock of minus base curves in semi-finished. Again, X-Cel can cast those for you, probably up to a -6 base. Us old-time lab rats would cut the back curve as high as the machine would go, in your case, -20, and leave additional ct to allow for regrinding. Then put the coarsest roughing pad you have on your final tool, say a -30, then rough the lens to the ct you need. Cut your myo on the generator to what ever bowl size you need, then fine and polish.

I suggest that you use a 35 mm sag gauge in order to get your sag measurements in a "reasonable" range (it makes it easier to calculate).

[other_bill_fea]

I would agree that X-Cel is your best bet for thick plastic blanks, as the plano base with a plano back curve is essentially a hockey puck.

Something to think about also would be free-form lenticulars, as they can give you a better look for some of the higher powers because it can tailor the edges to the frame shape, instead of simply being a circle.

[PRECISIONLAB]

Mike has it nailed with X-Cel being your best source. I use the minus BC 1.67 for high powers and block with a minus BC block. For our system (Step One) it is a convex gray block. For some reason thickness (CT) varies based on power. On the SL-2 I usually add 2.5-3.5 thickness and fine to final CT. I'm an ole timer so I have a pretty good eye for determining CT while lens is still blocked. I have book or log of thickness cuts for both high plus lenticulars and high minus myodisc as a reference guide for faster processing. This is the best way to learn the tendencies of your equipment

[LENNY]

I would agree that X-Cel is your best bet for thick plastic blanks, as the plano base with a plano back curve is essentially a hockey puck.

Something to think about also would be free-form lenticulars, as they can give you a better look for some of the higher powers because it can tailor the edges to the frame shape, instead of simply being a circle.

And SGX is perfect for FF!?!?!?

[other_bill_fea]

Obviously not, but if it's something that he does a lot of, I thought it would be worth mentioning. There's not really a reason he can't offer his patients an option between a 'basic' myodisk (that he can do cheaper and quicker in-house) and an enhanced one that he gets from somewhere else, either.

[other_bill_fea]

Obviously not, but if it's something that he does a lot of, I thought it would be worth mentioning. There's not really a reason he can't offer his patients an option between a 'basic' myodisk (that he can do cheaper and quicker in-house) and an enhanced one that he gets from somewhere else, either.

[LENNY]

Obviously not, but if it's something that he does a lot of, I thought it would be worth mentioning. There's not really a reason he can't offer his patients an option between a 'basic' myodisk (that he can do cheaper and quicker in-house) and an enhanced one that he gets from somewhere else, either.

BTW Welcome to the board!

[other_bill_fea]

Thanks!