Lap problem

[Rheaopt]

Hey everybody. New to the board and this is my first post. I have come across a problem since upgrading to a 3 axis generator. My old tooling in the lab is of unknown origin to me and differs greatly as power increases. Our tooling comes from a book that was handed down to me from my former lab manager which was given to him by his former lab manager. I think it was created to account for elliptical from old 2 axis generators. I have no clue what tooling index is or anything. My tools run something like this; 2 base reads 2.01, 3 base 3.03, 4 base 4.04, 5 base 5.07, 6 base 6.09, 7 base 7.12, etc. etc. Anyone have a clue?? My cross curves are cut to cylinder not curve. My tooling is in eighths; 6.00, 6.12, etc. I am in the process of changing to tenths on a standard tool index of 1.530. Is it possible to keep my tools cut to cyl.? If anyone has any ideas please let me know.
Sorry this was so long winded.

Thanks

[optispares]

Hey everybody. New to the board and this is my first post. I have come across a problem since upgrading to a 3 axis generator. My old tooling in the lab is of unknown origin to me and differs greatly as power increases. Our tooling comes from a book that was handed down to me from my former lab manager which was given to him by his former lab manager. I think it was created to account for elliptical from old 2 axis generators. I have no clue what tooling index is or anything. My tools run something like this; 2 base reads 2.01, 3 base 3.03, 4 base 4.04, 5 base 5.07, 6 base 6.09, 7 base 7.12, etc. etc. Anyone have a clue?? My cross curves are cut to cylinder not curve. My tooling is in eighths; 6.00, 6.12, etc. I am in the process of changing to tenths on a standard tool index of 1.530. Is it possible to keep my tools cut to cyl.? If anyone has any ideas please let me know.
Sorry this was so long winded.

Thanks

pad allowance

[Rheaopt]

I'm using pad comp. of .4572.

[shanbaum]

Hey everybody. New to the board and this is my first post. I have come across a problem since upgrading to a 3 axis generator. My old tooling in the lab is of unknown origin to me and differs greatly as power increases. Our tooling comes from a book that was handed down to me from my former lab manager which was given to him by his former lab manager. I think it was created to account for elliptical from old 2 axis generators. I have no clue what tooling index is or anything. My tools run something like this; 2 base reads 2.01, 3 base 3.03, 4 base 4.04, 5 base 5.07, 6 base 6.09, 7 base 7.12, etc. etc. Anyone have a clue?? My cross curves are cut to cylinder not curve. My tooling is in eighths; 6.00, 6.12, etc. I am in the process of changing to tenths on a standard tool index of 1.530. Is it possible to keep my tools cut to cyl.? If anyone has any ideas please let me know.
Sorry this was so long winded.

Thanks

6.00 to 6.09 and 7.00 to 7.12 suggest a 1.3mm pad compensation, which is humongous.

What do you mean, "Is it possible to keep my tools cut to cyl.?" What sorts of cross curves do you have now?

Whether cutting to 0.10D increments is a good idea depends on the materials you are likely to be processing. If you're going to go to the trouble of re-cutting your laps, there is probably a better scheme than 0.10/1.53...

[Rheaopt]

What would one suggest then? The tools are what were dealt to me and I need to upgrade soon. This is a good time of the year to do it cause we slow down some and I will have time to spend truing them.

[shanbaum]

What would one suggest then? The tools are what were dealt to me and I need to upgrade soon. This is a good time of the year to do it cause we slow down some and I will have time to spend truing them.

I can suggest something if you tell me what you think you're likely to be processing and in what proportions. Is it 50% CR39? 80% poly? All Hi-Index? Is it likely to remain that way for the foreseeable future?

[Rheaopt]

We run about 80% cr-39, 15% hi index and about 5% poly. I don't see it to change a whole lot in the next 5 years anyway. I work for some owners who still believe that cr-39 is the best thing out there. I am trying to get them to embrace newer materials, but it is slow going. I think mostly cause they don't want to put forth the effort to learn about them. If I would see an increase it would probably be in poly. It has been moving better than it used too.

[jherman]

What brand of lab soft wear are you using?

[shanbaum]

We run about 80% cr-39, 15% hi index and about 5% poly. I don't see it to change a whole lot in the next 5 years anyway. I work for some owners who still believe that cr-39 is the best thing out there. I am trying to get them to embrace newer materials, but it is slow going. I think mostly cause they don't want to put forth the effort to learn about them. If I would see an increase it would probably be in poly. It has been moving better than it used too.

Anytime you're running a preponderance of any material (and certainly when it's on the order of 80%), you should consider having a set of laps cut in the index of that material. When you do that, you really only need 1/8 diopter increments on the base curve, and 1/4 diopter increments on the cross - so a relatively small number of laps is required to cover the range you're likely to need.

My preference is to compensate laps for pad thickness in every case, but it's particularly important to do so when cutting an index-specific set; not doing so undermines the principal benefit of being index-specific, which is that there's a clear correspondence between the laps you have and the prescriptions you're trying to produce. You get very accurate cylinder powers (since the difference in curvatures on the padded laps are precisely the same as the cylinder powers ordered), and while there can still be rounding error on spheres, it's as consistent across the range as you can get, so that differences in sphere powers between the two sides of an Rx are precise in relative terms, even if the rounding error dictates that they can be 0.06D off by design in absolute terms.

Of course, that set isn't going to be useful for anything but CR-39, so you have to think about what to do for other materials. For the mix you quoted, using foam laps for everything other than CR is a good solution - if you are lucky enough to have a generator that cuts them.

If not, you have to choose between having two sets of laps, or having one set that's at least optimized in some sense for CR-39. You can do that by cutting laps in an index of 1.598, in increments of 1/10 diopter. That provides cross curves that happen to coincide with 0.25-diopter cylinders in CR - a 0.30D cross difference on the 1.598 lap is 0.25D on the 1.498 lens.

Here again, compensate the laps for pad thickness; there's absolutely no advantage in not doing so. The disadvantage in not doing so is 1) you again lose the benefit of precise cylinder powers in CR, and 2) the intervals between laps varies across the range of curves, and worse, you won't have base curves that differ in power (in CR) by 0.25D or 0.50D, the way prescriptions frequently vary in sphere power between the two sides.

The most significant disadvantage of the latter approach is, it takes a lot more laps to cover the same range, and a lot of those laps will be used only rarely, for the 20% of your work that isn't CR. If you can constrain your hi-index work to a small number of indices, it's possible to figure out which ones you may not need at all.

[specs2see]

hi there, i have to say that shanbaum's reply was one of the most informative i have seen on here.
he has listed tons of good information.
i also am concerned with the pad comp you are saying you have.
you need to get a good average on the pad comp, and then compenstae for it in your generator, assuming you have a 3 axis.
also if you are going to invest in new tools, i again agree with shanbaum.
invest in 10th d, and 1.6 index. the trends of cr39 are changing and at some point it will become a less and less used material.
80% cr39 wow. i jump for joy if i get 5 cr's a day..
good luck and let us know how things turn out.

Don Summers
VM Products
Full service lab and coating facility