3DPrinting

Haha so many questions 🙂 Thank you for your interest in my little project.

To address you questions:

Is there some forum where people discuss this? For tips and common pitfalls.

There is not. Not to my knowledge anyway.

The few usetul forums I found are reserved for people who work in the eyewear trade and they don't want you to participate. I tried joining by pretending to be a professional, but they either found me out by asking where my store was, or because I asked questions that no true professional would ask.

What I know, I picked up over the years (decades really) making my own frames. But the opticians don't like it when you make your own frames, because selling you frames is their bread and butter. They make almost no money selling you lenses. So they won't help you undercut their business, that's for sure.

You talked about the registration tab at length. I’m making mine not entirely radially symmetric. Does this mean I don’t need them? Will the lens wabble inside because its PLA?

Your correction may or may not need orientation.

If you have a simple myopia or hyperopia correction, it doesn't matter how your lenses are oriented.

If you have astigmatism however, your correction has an axis and the lenses need to be oriented correctly to within a couple of degrees. You can see if your correction has an axis in your prescription: it looks like an arrow with an angle.

Progressive lenses are also oriented, because near is at the bottom and far at the top.

With non-round lenses, that's not a problem: the edging machine will measure your frames and cut the lenses so they're oriented correctly when mounted in the frames. You can't really mount them any other way.

With round lenses - or near-round - like mine, the lenses can turn in the frames and you need some way to prevent that. Round frames are really the worst possible choice if your correction is oriented. But hey, I like them 🙂

Traditionally, if the frames are made of metal, the hoops can be closed with screws, and tightening the screws clamp the lenses and prevent them from turning. With plastic frames, in which lenses are traditionally clipped - possibly after heating the frames a bit - the fit may be tight enough for the lenses to stay put on their own. If not, usually the optician will drop a drop of superglue at the edge.

Also, typically with round frames, the lens maker or the optician will make a very small, almost invisible mark on the lenses to find the correct orientation should the lenses move. If your glasses are round, look very carefully around the edge of the lenses and you should see the mark - usually next to something obvious like the hinges.

If your optician didn't make a mark, they probably figured they'd measure your correction again to find the optical axis on each lens (they'll draw 3 dots on each lens) and then they'll line up the 6 dots. But it's longer and more annoying than leaving a mark.

With my metal frames - which I made myself - the lenses are clamped hard in the hoops. No problem.

With my 3D-printed version, PLA is much too weak to take a thread to tighten the hoops around the lenses with screws (or take inserts) and printing hoops that lenses can clip into securely without opening them up is really fussy (I know, I did it for a friend's glasses I reproduced out of PLA). And I sure as hell didn't want to use superglue on my super-expensive lenses - not to mention, I want to be able mount them and remove them in minutes with no efforts.

That's why I designed split hinges that close around the lenses when mounting the temples, and this registration tabs system to lock the lenses in place without applying pressure on them.

If your correction doesn't need orientation or if you're designing non-round frames, you totally DO NOT need the registration tabs. It's only for round, oriented lenses.

Does the frame slip more than with other material? Or maybe with a riding bow make it not noticeable.

In my design, yes, because like I said, the lenses are held in the hoops with almost no pressure. without the tabs, they turn very easily.

If you design non-round lenses, they might "creak" a bit if you try to turn them forcibly and the frames don't fit very tight around the edges. But they won't slip.

If you're designing clip-in frames and the fit is correct, they won't move whatsoever. But you'll need to print several versions of the frames with a few dimensions adjusted ±0.05mm here and there to find the right size to clip in the lenses with no major drama, yet with enough pressure for a proper fit. It's really quite a lot of fuss.

Was the optician able to bend the temples with heat or was no frame adjustment needed at all?

I never go to the optician 🙂 I like being independent for things I need in my life (I'm also a partial foot amputee and I make a lot of my own shoewear for the same reason).

I used to adjust my 3D-printed frames a bit with a hot-air gun. It didn't take long but I didn't like the repeated trial and error process. So I took the time to work the adjustments in the FreeCAD models, as I explained on my Github, so the final frames fit my face perfectly without any adjustment, right out of the printer.

The only thing I do is polish the nose bridge with 600-grit sandpaper to smooth out the "staircase" a bit (layers of PLA deposited at a 45-degree angle) and then chemically-polish it even smoother with acetone. I also chemically-polish the inside of the ear hooks but only when I print them with certain PLA filaments I have that always end up a bit rough for some reason, if it's a pair of glasses I intend to be wearing for many hours continuously, so the hooks don't irritate my ears. But usually with most filaments, I don't have to: the wires are very smooth naturally out of the printer.

You’ve made the lens groove in this triangle shape. Is that the standard or will the tracer edger pick up any shape there? How’d you decide how deep to make that groove?

There are many types of bevels. But that type seems to be the most common for "regular" prescriptions on fairly flat or slightly curved frames. Depending on how thick your lenses are at the edges, the bevel is placed more or less forward by the edging machine to hide as much of the thickness as possible at the front when the lenses are mounted in your frame.

Usually grooves for that type of bevel are called "hide-a-bevel" grooves or V-grooves in the literature. They nominally have a 120-degree profile from what I could read. Although in fairness, I measured a few old lenses I had lying around with a profile projector and they measured between 90 and 120 degrees. So if it's a standard, it's not a very well respected one.

There are other types of grooves. The frames I made for my friend for example didn't have a groove at all: the groove was a 0.6mm square groove in the edge of the lenses themselves, and the bevel was inside the frame hoops. Very strange! I had never seen this kind before.

There are also chopped bevel profiles for ultra-thick lenses, and "shelf bevels" for wraparound lenses, etc... Look it up: there is an almost infinite number of bevel types. And that's just for solid frames: if you frames have a wire at the botton of the lenses, then the top half of the lenses have a bevel and the lower half have a groove. The variety is bewildering.

Lens makers usually look at your frames and mount the grinding wheel(s) with the correct profile(s) in the machine - or if the machine is fully automated, the tool changer loads the correct grinding wheel(s).

Often, they don't even need to look at the frames: if you chose a standard model at your local optician, more often than not, both the frames and the lenses are sold by the same supplier - and usually they're in Vietnam or somewhere all the way around the globe, which is why eyeglasses take so damn long to make, in case you wondered 🙂 But I digress...

Anyway, one thing you can count on with almost absolute certainty is that all edging machines are capable of cutting a "hide-a-bevel" 120-degree bevel. That's why I chose that "standard" for my frames.

As for the depth, you don't really choose it: it depends simply on the width of the hoop. My hoops are 2-mm in width, which results in a ~0.5mm depth because of the angle. I indicate it in the picture on my Github for redundancy, just in case, but it's not strictly needed: all the lens maker needs to know is that's it's a bog-standard 120-degree bevel, to load the correct grinding wheel into the machine, or something close enough to that profile.

How comfortable do you find wearing PLA so far?

The glasses are SUPER comfortable. It's not really because it's PLA or some other material: it's because the fit is perfect for me. It's like shoes or clothes: bespoke always feels better.

If you take the time to design your own frames to perfection - be it 3D-printed or made using traditional methods - when you hit the right dimensions, you'll know immediately: they'll be the most incredibly comfortable glasses you've ever worn. And when you do it yourself, you have all the time in the world to make the fit as perfect as you want it to be, something opticians don't have time to do because, well, they have to make their time worthwhile.

Finally, my glasses weigh 14 grams all told. That's VERY light and it goes a long way towards making them comfortable. That's definitely a plus and it's entirely due to the 3D-printing process.

I hope the above answers your question 🙂 I wish you good luck with your own design endeavor