Surfacing with shape

[leestaniforth]

Hi All,

If i send a shape with every order to the generators, what are the production time implications / considerations?

thanks

[WFruit]

Having the shape is always better since your software can more accurately calculate needed blank size and lens thickness. Thickness won't be as big a deal on minus lenses, but it will make a HUGE difference for plus lenses.

It really shouldn't make any difference in the time it takes to run the lens.

[shanbaum]

Hi All,

If i send a shape with every order to the generators, what are the production time implications / considerations?

thanks

Having a tracing available to your lab software will afford the benefits WFruit enumerated; but if you're thinking of having your generator crib to frame shape, don't do it. In most cases, the shape will not be centered on the surface block, and even if it is, the actions of smoother and/or polisher will be uneven across the surface of the lens, unless the shape happens to be quite symmetrical (e.g., an oval or circle centered on the surface block). It would be similar to surfacing with an off center stroke pattern.

Aside from cribbing to shape, I don't know of any use to which the generator would be able to put the trace data.

[WFruit]

Using a generator to crib the shape of the lens is such a bad idea it didn't even occur to me that it was what the OP meant.....

[MikeAurelius]

I'll third that opinion...with the understanding that cribbing a lens down from 75 mm round to a workable 68 mm round, is almost always done by the lab, again, depending of the frame size and the amount of total decentration in the lens. Single vision isn't a problem, prism is generated in to achieve decentration, but multifocals/progressive are always problematic.

[Darryl Meister]

In most cases, the shape will not be centered on the surface block, and even if it is, the actions of smoother and/or polisher will be uneven across the surface of the lens

I imagine that a lens cribbed to the frame shape will tear up the fining and polishing pads more rapidly as well.

Best regards,
Darryl

[MikeAurelius]

I imagine that a lens cribbed to the frame shape will tear up the fining and polishing pads more rapidly as well.

Best regards,
Darryl

Well...it depends on whether or not there is a chip bevel around the edge of the lens and/or how far off the generated curves are from the tool. All things being equal (chip bevel, curve correct), a cribbed lens won't tear up pads.

[Darryl Meister]

Well...it depends on whether or not there is a chip bevel around the edge of the lens and/or how far off the generated curves are from the tool. All things being equal (chip bevel, curve correct), a cribbed lens won't tear up pads

I'm referring to a lens cribbed to the shape of the frame... You have a much smaller blank size with corners, which cycles over more of the pad. I imagine that felt pads, in particular, would be subject to excessive wear over a 4+ minute polishing cycle. If the lens is significantly offset on the block, so that the pin pressure is applied relatively close to one edge, you would probably further exacerbate this issue.

Best regards,
Darryl

[LENNY]

So whats up with CTO?

[leestaniforth]

So whats up with CTO?

Hi, sorry but my question was "sending" via lab software. Not the generators do it. We currently use a combination of centre thickness optimization and "design shift so are currently producing many lenses with shape. The knifing problem is worked around via either a finish on a manual line or adjustment of et violation settings/ marco's
I was asking more about increased generator times and shorter polish times, coupled with possible increased coating issues.
Wfruit.. do you coat in house coat, and if so any issues.

thanks again.