problem with diameter size on free-forms

[casting guru]

Hi all, I'd like to pose a question here to see if I'm the only one having this problem on a regular basis (note: on a regular basis, not just once in a blue moon)...

I don't do too many free-forms (for various reasons)... when I do, I get them un-cut, from a variety of labs. But I ALWAYS have problems with the finished (cribbed) diameter when I receive the uncut. Especially on plus lenses. It's gotten to the point that I refuse to order a plus RX in a free-form, b/c I KNOW the blank is going to come to me at 55mm! But lately, the minuses are coming to me that way also. And this happens no matter what frame dimension I specify (I can order a minus lens using an A & ED of 60, and the uncut will come to me cribbed to 55mm!!). It seems like NOTHING I do on my end to try to increase the crib diameter helps.
Furthermore, when I talk with the labs, they tell me that they have no way of controlling the crib-diameter (this is ONLY applying to free-forms, not on traditionals). It seems that these are all IOT designs, and they are produced in various labs, but the problem is consistent.

Does anyone else have this problem, and does anyone have any advice? I have not worked on any free-form generators, (we only surface traditional with a Gerber/Coburn in-house) so I really don't know anything about the equipment itself and how to get around this.

[Wes]

Interesting. You should want your plus lenses to be as small and thin as possible, but I see no reason for them to make the lens so small that it won't cut out according to your specifications. Is this an issue with multiple labs? The cribbing can be adjusted for whatever size you need, or none at all on the cnc generators that I've seen.

[casting guru]

Wes, exactly... you want your pluses to be TAP... but I can never get them to cut-out! (unless it's like a 45 eye or something, and then I'm probably not doing a free-form anyway for a bunch of other reasons!)

Yes, this is a problem with multiple labs (both big & small). I've never operated anything but our Coburn SL2 (actually, it's NOT a "Gerber/Coburn"... it was the last run of SL2's before Gerber bought Coburn). I like our SL2, b/c we can adjust the eer-lovin' CRAP out of any setting... I'm talking knife-edge! But I just don't know how to get these free-forms to increase the crib on pluses.

But it sounds like I'm the only one having this problem... which only makes me more puzzled!

[Wes]

Are you sending an electronic trace, or measurements only? Have you discussed this with the lab manager and explained that they'll lose your business if this continues?
Id like to add, if multiple labs are doing this with multiple accounts, the stink would be enormous. However, if multiple labs are doing this only with you, perhaps there's a glitch in your end.

[casting guru]

Wes... sending measurements only.

Can't cut off my business with those other labs, and don't really want to. They do good work otherwise. It's really just these free-forms.

Yes, I really have been thinking that it must be something on my end, b/c if it was really a systematic problem then everyone would have it and we'd all know about it! So it's got to be on my end. But I just haven't been able to figure out what it could be... I only have the problem on the free-forms. I can order an uncut plus in some other lens design, but traditional, and I can manipulate the frame info when I order and then get the exact edge thickness that I want (i know how to control it even if I'm not surfacing it). But it's only the free-forms, that no matter HOW I order it, it ALWAYS gets cribbed too small!

[hyperoptic]

Hi Casting and Wes,

When running freeform if you can send a tracing that is by far the best thing to do, but if not we can design a lens based on a complete set of box measurements as well. How far off is the lens from cutting out? What design are you using? what are the powers (I know we are talking pluses but how plus)

If you would like to discuss this via the telephone, my number is 336.529.9284

Thanks

Kurt