Make Your Own Optical Lenses
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- Опубликовано: 15 май 2024
- Today we're making lenses with epoxy, using a replication molding technique. It... mostly works 😇
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==== Details ====
We can replicate lenses using silicone molds and optical epoxy resin. But there are a lot of caveats to this technique, and little hiccups that will ruin the optical finish. To achieve an optical finish, you need surface roughness and figure deviation in the nanometer range. This means curing temperature and shrinkage become major sources of error.
Residual stress in the molded parts can be assessed with polarized light and a polarizer in front of the camera.
==== Prior Videos ====
Injection molded lenses: • Machining an injection...
Microlenses: • Molding a Microlens Array
==== Materials ====
Mold material: Smooth-On Mold Max XLS ii
Optical resin: Smooth-On Epoxacast 690 clear
==== Analysis Equipment ====
nGauge AFM from ICSPI (www.icspicorp.com/)
Phenom XL SEM from Thermo
Gwyddion for AFM post-processing
Blender for 3D AFM rendering
==== Timeline ====
0:00 Intro
1:09 Replication Molding
3:04 Alternative mandrel material
3:37 Molding and casting technique
4:30 Fabricated lens examples
7:26 Molding priorities
9:38 Molding materials and considerations
10:49 Mold release difficulties
14:30 Shrinkage difficulties
16:04 Effect of Temperature
17:20 Internal stress and polarized light
18:51 Mechanical difficulties
19:40 Alternatives to silicone?
20:40 Direct molding off mandrel?
21:45 Refinement for future work
23:45 Concluding remarks 
Наука
*Note about the audio* 🚨 Sorry for the noise gate issue! The SEM is in the same room and has two pumps running continuously (diaphragm pump + turbomolecular pump). I cover it all in acoustic material, but there is still a lot of noise to clean up. And apparently I did a bad job this time (combination of noise removal in Izotope and gating in Resolve). Apologies for the audio discomfort! I edit with headphones on, but probably went numb to it after a while and didn't notice. Luckily, it should improve soon... the SEM is moving to a new room in the near future 🙂
*Addendum* It seems I overstated how hard it is to grind and polish polymers! Several folks have informed me that e.g. eyeglasses are mostly polymers these days. I'm not sure what kind of tolerance they hold relative to glass lenses, but clearly it's a mass-produced and probably polished on-demand for each prescription. I suspect it's still a lot harder to DIY good polymer lens grinding than glass though.
I really appreciate the honesty, most creators would just ignore a slight issue like this. Well done !.
Still better sounding than 90% of RUclips videos! :)
Just consider making the "release" of the gate/noise remover a bit longer or go with an expander instead and it won't be so noticeable, or even consider layering in some pink or brownian noise (or background music) back after the removal to avoid the total lack of noise.
Most noise filters or multi-band expanders/gates also let you adjust the frequency band it works on the most. You can hunt down those upper-mid early reflections that are giving you the most audible trouble with overall less noise removal.
Also, never forget the inverse square law: the closer you can get the mic to you and the further you can get it from the noise source, the easier your life will be in post. Likewise, if there is a specific noise source, rather than putting the mic in a traditional spot (e.g. above the head or near the camera), point it so the null of the cardioid pattern (i.e. back of the mic) is pointed directly at the noise source. You're only getting maybe -6 dB rejection on the side of the mic in the traditional arrangement, but in the null you might get -15, -20, even -30 dB through most of the audible band on a small diaphragm condenser.
If you layer a long piece of just noise floor audio from anywhere (doesn't have to be your lab) put it under your audio at like -40db to -30db it'll remove the jarryness of the audio cuts.
Great to see that this was noticed, it's a small thing, but it's good to see you care. I really enjoy the videos,
i do not notice it at all, listening through my speaker, even if i try to. As @Sam Gossner wrote, you sound better than many other youtubers.
The definition of "home shop" seems to a bit fluid, but maybe that's just me ;)
"making optical-quality surfaces [...] is really hard to do in a home shop, I don't have a single-point diamond lathe."
"just sputter some silver onto your glass in your sputtering chamber..."
"let's look at this under the SEM / atomic force microscope..."
Just joking of course, awesome content, very interesting.
Haha, ok that's fair 😂
I thought the same in those exact instant.
@@BreakingTaps I am just amazed by the quality of some of the home labs out there. TheThoughtEmporium is also quite amazing if it comes to home labs.
Some home shops are better than others!
That's hilarious! ... but I think you missed the point altogether.
The point is, that it is a demonstration of a guy who has these things IN HIS HOME SHOP.
Of course, that gives us husbands clear proof that the best makers NEED these tools!
Okay, I will admit the scanning electron microscope may be a bit pricy, and never in stock at Home Depot, so my wife can better justify a SawStop tablesaw with less bickering.
hmmm... i did a few things but improved the surface by spin coating the optical elements in a second step with resin. The layer is very thing to the spin coating but finishes the surface to much higher perfection.
Spin-casting should be good for making a reflective mirror. By adjusting the rotation speed you could in theory make different focal length mirrors.
@@peterjf7723 Yes, just by spinning the epoxy in a container, the surface of the epoxy would form into a perfectly parabolic shape thanks to centripetal force.
@@poptartmcjelly7054 I wonder how good the optical would be.
Could you expand on this just a smidge, it sounds interesting. Are you spin coating the pattern/mandrel, the mold or the part?
@@peterjf7723 bubbles might cause a problem with the surface and the uneven distribution of heat within the epoxy might add distortions also but i think it would be fun to see it tried out.
Very cool! The surface finish and actual shape (I forget your actual word for that) look amazing! I have to say I’m drooling at the thought of a diamond lathe for making aspheric curvatures but I’m afraid to look up the cost…
You can probably get a monocrystaline diamond cutter from china fairly cheap, then any cnc lathe will do a good enough job to test things
Yeah, not half bad for such a janky setup! Definitely not going to put Leica or Zeiss out of business any time soon though 😂 I did some poking around and it seems entry SPDT lathes start around 350k USD. It's not as much as I expected, but still a pretty darn expensive single-purpose, niche tool!
@@BreakingTaps Take a look at Huygens Optics channel.
@@BreakingTaps I won't call it cheap but I was expecting, at least, one more zero on the price.
Yeah I was really expecting the same!
You have a great presence in your videos. The lack of BS and depth of technical combined with an accessible persona is great. I look forward to every video, often in topics I didn’t know I was interested in .
@ebrewste I feel the same way, thanks for putting it into words.
...And kudos for the way you did, keeping it short while capturing the essence is not easy, (at least for me:).
This was very interesting for me. I am a mechanical engineer and usually watch makers on RUclips such as yourself so i am happy YT recommended this vid. As a person who wears glasses and get them scratched in no time, making my own lenses at home would be awesome!
Regarding stiffness issue, maybe use a CNCed part the is "pretty" close to the lens you want, so the silicone pour you need is just a thin layer. I know you will hit the issue of silicone not adhering to this stiff base, so maybe CNC also some "holes" (|like a mesh), so silicone has a lot of mechanical grab.
Really nice that you share the issues you found, I think that is the most interesting part. When things work, those are more boring ;)
Was going to suggest this. Reducing amount of error the silicone can introduce may reduce overall error.
I think this would help a lot! Didn't occur to me at the time, but yeah, some kind of "pre-form" I think would help to both provide mechanical support, and reduce silicone consumption (which also means it would cure more uniformly due to thinner, more consistent layers). Good idea!
i was going to comment that theres no way a CNC he could get would be able to produce a mirror finish but i realized i read the comment wrong. :(
As a bonus, the metal preform should act as a thermal mass and keep curing more even (and could be water-cooled much more easily than a silicone mold, I imagine)
Hmm... i should try this. I've been making deformed lenses from cyanoacrylate. The whole point of those is to have optical quality "blobs". They give uneven ghostly images when used with RGB leds, deliberately breaking the smooth beam. As the RGB elements are slightly off set from each other, each individual led gives its own distorted image. But because they are so close to each other, you get similar shapes, for ex arc where one side is blue, one is red with a green band in the middle. When you slowly fade them out, it animates the image.. Very, very beautiful.
This experimentation started from using crumpled mylar as a reflector. It just loses a lot of strength and it is difficult to get it at optimal distance. But distorting the image at the source, i get must clearer image. I add layers of cyanoacrylate, let it drip using accelerator in the other hand to freeze the shapes in place.
Do you have video clips of this? Sounds amazing ^^
Agreed, please share some images / videos / words on the process!
Dang, I need to see the resulting images of this
Would be curious if you could use a non silica glass, like CaF2 or MgF2 to avoid to silicone/silica bonding issues with the mold and not require sputter coating
Oh, I hadn't even thought of non-silica glass. That's a very interesting idea!
While lenses made from fluorides exist, they are reasonably expensive compared to glass lenses. I imagine the simplest and cheapest way would be to buy lenses that already have some sort of coating, or spin coat and bake them yourself.
Or AR coatings. Some of which might not be too hard to sputter/evaporate so you've got a leg up on that one! (Again, give or take size of pattern/mold fitting inside the chamber.)
@@T3sl4 I mean, the matter of fact is that he actually has the necessary equipment to sputter lenses himself, so what we are all describing are ways to do it if didn't have that.
@@graealex Well, ZnSe lenses are a thing and actually somewhat cheap since they're used for CO2 cutters
Loving your content so far. I can see your channel growing exponentially in the near future!
Your vids are always interesting, your production quality outstanding and your presentation is spot on.
Consistently excellent and one of my favourite channels for all of those reasons!
Hi Zach, nice work. I was wondering what your ultimate goal is exactly. If you want to make spherical surfaces, you should not start with a spherical mold, because then you will end up with an oblate elliptical surface, due to the volume shrink. So for making spherical surfaces, you need to start out with some kind of parabola/hyperbola. By the way, if you want to make epoxy/glass fiber mirrors of high quality (for example for telescopes), maybe reconsider: it is technically virtually impossible. I can mail you a few references if you want.
Ah yeah, that makes sense! Can account for shrinkage by adjusting the shape of the mold first. 👍
Would definitely be interested in those references! I've seen a number of papers in regards to replicated CFRP telescope mirrors and while they all highlight challenges (molding distortion, fiber print-through, differential thermal expansion, moisture absorption over time, etc) none of it appeared to be insurmountable. But perhaps once you consider all those challenges in aggregate it just becomes too hard to produce something optically good enough for a telescope?
Definitely going to pretend I didn't read that it was impossible and continue trying though, haha. A guy can dream 😁
@@BreakingTaps I'll admit I have zero experience with epoxy but an idea came to me. Could you cure the epoxy at elevated pressure? I'd assume it would make the final part higher density and maybe get rid of most imperfections making it a feasible technique for optical parts. Could also help with the uneven forces on the mold.
Great to see some favorite optics guys know each other...
I am a noob and I know this sounds a bit bonkers - but I wonder about some out of box approaches - thinking about how fresnel work - I wonder if building a lens or mirror - micron by micron, so you can control refractive index and chromatic aberration and internal reflection
Is possible in a well appointed home shop. You and Applied Science channel could have a fun go at it !
Might be a bit out of my skillset, but there's some neat work done in this area using two-photon lithography. Basically does exactly what you said: prints them up layer by layer at a small enough scale to avoid aberrations. Check out this paper for example (open access: www.frontiersin.org/articles/10.3389/fmats.2020.586496/full ), they print lenses on the end of optical fibers. Pretty cool!
Sweet! I was just riffing- sounds like I have some fun homework!
@@BreakingTaps The link is broken - love your community engagement, keep it up :)
@@karim1485 Fixed, thanks for the ping!
This was such a good, helpful and well-researched video! No time wasted and the extra stuff such as diagrams and putting lenses through polarised light to show the tensions makes such a difference in understanding wtf is going on. Thank you!!
Coolest channel! I love understanding these processes that are normally out of reach because they are so industrialized. Not to say that it's easy to create a great lens but understanding the principles brings me great joy!
Can you use a lens with anti-reflection coating (MgF) to prevent sticking of silicone?
Hmm that's a good idea. I'm not sure, but probably! Not sure how durable those coatings are so it might start to degrade but if you can get a clean mold off the first time it shouldn't matter.
@@BreakingTaps Being hydrophobic, it should be fine. The AR coatings are PH sensitive though, not sure if that's an issue. I work in a digital eye lab and we use lye to strip AR coatings, but it is fairly stable in things like alcohol. You might have better luck with a composite mold with glass on the top and bottom, and silicone walls. The lens blanks we use are injection molded against precision ground glass, and then we surface the RX on the back (so every lens basically begins its life as a hockey puck). Most eyewear is made with plastics, and surface roughness and haziness is reduced with some fine polishing using aluminum hydroxide, and the varnish anti-scratch coatings cover up the rest. I wonder if you could replicate a hardcoat being spun on, though we use very high RPM's to avoid pitting. Just keep in mind that the refractive index of that epoxy must be awful even compared to the cheapo plastic CR-39 lenses, but it might actually be a step above acrylic lenses like the ones you might find with some magnifying glasses.
@@eapellow9767 👍 this is a pretty ambitious project for home gamer, some other mentions, the backside of the lens is ground with a domed tool made aluminum with about 600 to 800 grit paper stuck to it. constant flow of water. then a polishing process, which I'm gonna skip commenting on to mention. I agree coating the lens if done correctly will improve the optical quality there is spin coating and dip coating.. after a suitable "hard coatimg" try and do an anti reflective coating with the sputter process. and hydrophobic coating to protect it.. again part of those process has multiple issue to contend with but being the 2nd guy I've seen on RUclips sputter coating in the garage and I worked in an optical lab for years i seen alot of equipment. and I know labs use them but I had never seen one (sputter coater), until RUclips. that's awesome
I'm glad you decided to make and upload this video even though you didn't perfect it. Love the video format!
Absolutely loving your content. Keep it coming!
You could polish the lenses before hand to remove some of the imperfections. Then you will want to spin coat a low viscosity mold release to get a smooth surface. degassing the resins premixing will let you degas it better/more gently once it is mixed. If you sputter coat the glass lens with silver as a mold release you could get a perfect surface. Since it has no silicon in it, it wont stick.
Dude you're the first to do this thank you I was wondering why no one had ever done this I looked it up months ago to see if I could do this myself but no one has ever I guess until now.
Spdt sounds really cool, didn't know how those molds were made, this channel is amazing
I worked for years in a surface lab lapping and polishing plastic lenses all day. It's absolutely practical
You're really thorough and knowledgeable with a soothing voice. Subbed.
Instead of sputtering metal on to the glass lenses, you could try an oleophobic coating that once applied and then polished off leaves a nanometer-scale fluorine-based layer on the glass. Try talking to Aculon in San Diego.
As you alluded to, you probably want to minimize the thickness of the silicone molds and bond them to a steel plate with cooling channels so you can actively cool the parts while curing.
For the single-step molding, you can use an optical grade silicone (yes, you can make silicone lenses, I've seen a few very nice examples).
A longer runner might help reduce the stress at the gate location.
The chromatic aberrations you are seeing are likely caused by dispersion. The epoxy you are using likely has a high dispersion (low Abbe number). The common method of canceling dispersion is to combine high and low dispersion elements (classically this was a flint and crown glass element).
Do note that your lens copies won't match the glass originals, even if you perfectly copy the form and eliminate all stresses, as the refractive index and Abbe numbers will be different from that of the glass.
I didn't expect this much knowledge and experience from a YT video, this is a paper worthy type of information
What an amazing job!
I'd suggest post-curing the ready lenses in an oven at about 85 Celsius before disassembling molds. This is used for ordinary epoxy in order to make it stronger, but in your case it may relieve internal stresses. The post-cure temperature is close to melting point of the epoxy.
An another trick may be - create lens with say 95% of the desired thickness. Post-cure etc. Disassemble mold. Then add some epoxy on both sides, assemble and cure, post-cure. Ready. You can try to defeat shrinkage in such way.
This is really neat! I may actually play around with this. I actually have some smooth-on silicon and acrylic resins. Would potentially be cool to cast a lens in the inverse of the type you wanted. Say if you wanted a concave lens of a certain camber, just cast it in a convex lens of the inverse camber.
seems like glass would be a good backing material since it bonds to it, and it can be pretty rigid
Hah, yeah I think so! Didn't think of that at all, but dropping a piece of plate glass or similar on top (or even chopped fibers into the silicone) would probably stiffen it up nicely. Will keep that in mind for future projects!
Thank you so much as always!!!
When I find time I will absolutely try this out with some fresnel lenses!
That's a really interesting project!
I guess the biggest step is the stress-free curing of the epoxy so that you get rid of the birefringence.
(just a small comment: the noise gate on your audio is a bit disturbing when listening with headphones. Don't be afraid of a bit of background noise...)
Hey! Great video! I'm glad you liked the metal coating for mold release trick from the micro lenses video!
🤗
Absolutely fascinating discussion. Thanks.
Eyyy
Since silicone bonds to glass, why not use a glass plate as a backer when you're casting the upper half of the mold? Then it would support against sag when casting the lens.
I really appreciate your videos! It is neat to see what can be done at home.
I am not going to make any lenses today but i definitely learned a lot! Brilliant video!!
Your videos are inspiring. Thanks for doing what you do.
Oehhh, instant like. I was waiting for it since your Twitter message. So love this channel. :)
Love your content mate. Would be interesting to hear what you do in your day job and how you got started!
This is great. Looking forward to your next video about mirrors. Do you have an end use for the mirrors? A telescope could be a really cool use for direct carbon fiber molding technique.
I too am excited about your next mirror episode ... As I have a 50 year old telescope to remirror
I was similarly curious about telescope mirrors but more for making a high-zoom compact monocular based off something like this: ruclips.net/video/HxwhCmO90UQ/видео.html
this channel is a goldmine for people who like people making stuff
Incredible work as always !
This is great information, thanks for sharing! I would add that you can use acrylic resins and optically clear silicone to make lenses. Be careful not to buy acrylic that contains mercury - it's often used in cheaper products to make it clear, and it's toxic when liquid. The refractive index of plastic tends to be lower than glass, so expect the lens power to be different from the glass original. To get around the thickness problem, you could try moulding thin layers of epoxy in an open mould to gradually build up thickness. Then when the lens is almost reaching the other half of the mould, put the lid on and do the final surface with it closed as you would normally. To get rid of bubbles, you can put the entire mould inside a vacuum chamber or use a machine to vibrate the gas bubbles out.
The carbon fiber mirror idea is excellent. Thanks for sharing the knowledge you gained with us, for free.
So chill, I made one of these for my Rink building maintenance refrigeration engineering book, so I can magnify things around the arena!
you should try the rotating mold method for creating large parabolic mirrors. observatory mirrors are sometimes made this way. they just have a huge plate that rotates at a fixed rate and they pour molten glass on it. the glass naturally forms a perfect parabola from the rotation, and hardens.
It seems like dropping a glass backer on the freshly poured silicon would be a good combo as silicon likes to bond to glass. Also using much thinner silicon pour would reduce flexing with that technique. 3D printed mold walls with surface features to give a mechanical bond to the silicon would also aid in making a more robust mold block along with the glass backer. Assembly and injection features can also be added easily to the 3D printed mold wall.
Thanks for sharing your work with us.
Wow I've been looking for this kind of video for about a year. I'm trying to figure out a way to make a cheap spherical mirror with a good optical quality out of epoxy. Haven't started yet but this video will be a goldmine for this project (and I'm hyped for the one about mirrors obviously).
One particular detail that catched my eye is the bubble defect at 10:20. Did you noticed how sharp the reflexion are on the bubble spot? Maybe using bubbles can solve multiple problems like: having multiple steps using silicone molds that introduce imperfections or getting a perfect spherical surface since the constraint from a gaz is usually uniform. Unfortunately I think bubbles will obviously be very sensitive to themral shrinking gaz will expand due to the epoxy warming up so it might be difficult to control but this is a nice track to keep in mind.
What about using the glass lenses themselves as part of the mold? That way you wouldn't need to worry about lenses sticking to the silicone.
Does the epoxy stick to the glass and thus it wouldn't work or could the silver sputtering be used to provide a removable coating like now but again without the intermediary?
Pretty sure that's what he's doing in the "Direct molding off the mandrel" section, ruclips.net/video/mfAGivG9Koc/видео.html, using the lens of opposite curvature as a mould for a mirror.
This is actually quite close to one of the techniques I'm trying with the mirrors! Epoxy... sorta sticks to the glass. It's not permanent, but it can be _very_ tenacious. I think I've ripped a few chunks out of the lens too on accident (around the edges). So some kind of mold release is still generally required, although you can play some tricks with heat to demold (freeze/thaw cycles can help break them apart since they have different expansion rates)
Bloody fantastic. Thanks for doing this
Thank you, I needed this. Can't wait for the mirror video. I've been experimenting myself with different chromium paints, but it just doesn't reflect enough. Seems I need to build a sputtering machine
Great breakdown. Since silicone adheres to glass, you should use a thick glass surface as a backing on your molds so they hold their shape without sagging. Glass can be pretty stiff so much better than nothing.
Great video, I might have to try this. Have you thought about resin curing speed? I'm thinking some of the really slow curing resins might produce less internal stress.
That's really interesting! I wonder if after it's ready you could place it in a turntable, with one of the faces up, and then pour some epoxy over it, so the resin will flow all through the surface and the gravity+ centrifugal force will smooth out the kinks
Consider using Rustoleum Mirror Paint as the mold release for the resin; the paint will make a first surface mirror against the silicone, but bond to the resin when you pull it out.
I think this will work because the mirror paint makes a striking second surface mirror when applied to the inside of glass.
I just don’t know if you want the paint wet or dry before pouring the epoxy in…
Amazing information! Thank you for your great videos!
I spent some time on a DIY digital microscope and was wondering about improving the ratio of field of view to magnification on top of easily available arducam sensors, so this was very informative. Great organization to the video - you walked me through all the factors effecting the end result quality with attention to alternative materials and processes as well as your decision making process.
Outstanding. I hope to make a DIY system to reliably create the lense profile in a diy shop.
Thanks for the finishing details on the CNC process.
Why did you give up on the injection process?
Thanks for sharing. When I saw the first 3d printers I was instantly interested in making eye glasses. You can get the shape, but the surface roughness is far from nano-meter smooth
Maybe you could purposefully add a lot of internal stress to the lenses to make a Gradient-index lense. They use an optical density gradient rather than normal refraction, so you might not need to worry about surface quality as much? Idk. It might work especially well because you are already working with epoxies and I think you can use a uv resin and cure different parts at different speeds. It might also be extremely hard to do, but could be a fun project.
Are there adjuncts you can add to the epoxy to set the refractive index? Also, when the refractive index is being measured, is there a lightwavelength (or chroma) standard to do this at?
Great questions! So the answer is.... maybe. I've been looking through literature and there are some exotic chemicals you can add to epoxies to adjust their IOR, but it doesn't appear to change it _much_. There are also some papers which dope the epoxy with metal oxide nanoparticles (titanium dioxide for example). The idea is that the nanoparticles are small enough and the concentration low enough that it doesn't affect the transparency too much, but being nanoparticles they can have a big influence on refraction. I'm chasing a few leads there, we'll see.
When people say the "index of refraction" as a single number, it's referring to the IOR at 589nm (yellow light). Historical quirk: it's the average of the doublet emission lines from burning sodium and folks started measuring at that wavelength. But all modern glasses have a set of constants defined which you can plug into an equation to get the IOR for any specific wavelength you care about, the single number (1.56 for my epoxy) is just shorthand to get you in the right neighborhood basically :)
@@BreakingTaps Here's a bizarre thought: If you were to 3d print plastic lenses rather than cast them, you might be able to fix chromatic aberration by adding dopants accurately to layers within the lens. It wouldn't have to be a surface coating, as I think is done with glass lenses.
could you use heat, to partially liquefy the surface of the lens, to get a smooth, clear surface?
You should definitely try two-component polyurethane rubber casting. It has almost the same properties of the silicone except it won't stick to glass at all. It does stick to epoxy by some degree but it is ok to cast some parts. It is commonly used to cast concrete and is pretty easy to obtain. I have worked with vytaflex-30 and it is a good start to try.
Interesting, I had no idea! Haven't tried playing with those yet, so not at all familiar. I'll pick up some, thanks for the tip!
@@BreakingTaps I should also note it can replicate very delicate parts (fingerprints for example) and overall is a solid alternative to silicone. It is less popular than silicone in a hobby due to its lower shelf-life (3 months at max after opening the can), but professionals use it a lot.
I'd give cerium oxide a chance even if it isn't supposed to work. I used it on a scratched up hand magnifier and got it crystal clear again. (Applied the abrasive to one of those eyeglass cleaning cloths with water and gently hand rubbed evenly for about 20 minutes) I don't have a way to see how much its figure changed though. I don't know what the lens is made out of but am sure it isn't glass. The material seems to have been selected for ease of scratching.
Do you suppose there is any chance of success for making spin formed epoxy mirrors at home?
Interesting, will look into it! Perhaps the CeO2 slurry still reacts to plastics, even though it's not quite the same chemistry as glass? Cheap enough experiment to try!
I think spin-forming could be done, but the main stumbling block would be vibrations I think. Probably needs some kind of air spindle to minimize vibrations in the system?
There are "Solar cigarette lighters" made out of metalized plastics to light your cigarette in the sun. They aren't too bad optically and quite cheap. I tried to make a little spotlight out of one and it worked out great.
I did my own lens with epoxy by using sandwich bags and air.
Great video! I have been thinking about making larger plastic lenses for DIY telescopes...just didn't know where to start...but your video has now sparked my ideas!
Have you use distilled water to make sure the glass lens were really clean?
Thanks! And yep, I had to do a thorough cleaning of the lens make sure the sputter coating would stick... if it had any oil or residue the metal would not deposit uniformly. I used acetone -> IPA -> distilled water to clean them. Probably overkill but it worked :)
I was reading an article yesterday about some guys making lenses using UV cure polymer floating in a suspension of equal density fluid. Having it suspended in fluid counteracted the flattening effect that gravity has on fluid over a certain volume.
Wonder if you'd try that technique out and compare.
2 questions:
Is it possible to polish epoxy lens?
Have you put the mold inside a vacuum chamber in order to avoid bubbles forming?
As for the mold release. Have you considered spin coating? I know i show up late to the game. But i figured this might do in future projects. Also, a mold release per se has only the job of preventing the two parts forming any kind of bond. So maybe the commercial mold releases are not the best choice. An (to the processes involved) inert liquide with adequate viscosity and surface adhesion might do the trick.
Love your channel! 🤗
After seeing your video on atomically flat surfaces I got an idea to bring this together with the molding of lenses. Assume you use a thin mica sheet as the defining surface in your molding process. You could then get an extremely flat surface. Hopefully the mica sheet is flexible enough to allow some radius of curvature (think of those adaptive mirrors which is deformed deliberately).
Mica might need a sputtering step in case it sticks to the epoxy.
Viable?
Is there a problem using flame or heat polishing for dealing with fine mechanical roughness in the plastic lens?
Have you tried freezing your plastics before you lap or grind them? IDK if the improvements in grinding may be offset by the thermal deformation but maybe worth a shot
i think you and ben would make a unstoppable youtube combo.
Something I've learned long ago when it comes to cheap optics is that it's usually better to find cheaper ways to makes optics out of good materials than cheap way to makes optics out of cheap materials. There's really not a good substitute for glass, both with mirrors and lenses. What should be done instead is finding a way to build or replace glass making machines that cost less but that delivers good performance.
Hello, do You think it would be possible to mold very fine fresnel lenses this way? Would the silicon mold and final resin cast detailed enough to behave like a fresnel lens?
Silicone rubber is used for making statues that are big. The silicone rubber is supported by cast plaster usually after the statue is coated with rubber. Typically like a mask of a face is made. So the surface has a lot of features that the plaster can hold the shape of the rubber. So the plaster casting is removed from the rubber and then the rubber from the cast part. plaster can have cooling tubing. Actually you do not want a high thermal conductor if you can keep the heat generated by the epoxy or low. Even thick parts will tend to have uniform temperature epoxy. To plan the cooling add up the thermal conductivity of the epoxy at a tangent to the surface to the center. Add the thermal resistance of the silicone for it's thickness and then the plaster to the cooling.
Very neat idea and nice information! You might be able to make complex lenses that don't currently exist.
I wonder if a quality "wrap" or tinting film material could act as a release agent. Not sure of its optical quality, but could easily conform to the lens surface with some heat. Appreciate the shared experiments...
I remember the good ol days when we didn't have no e-bikes or e-mail we certainly didn't have any fancy e-poxy.
Great vid
Could you polish plastic lenses if you chill them to cryogenic temperature first, and keep them cool throughout the polishing process?
Thought this too
would something like inhibit X work instead of mold release? i heard it being used to make dice molds and it should leave only a really thin film on the lens
Super cool, got a sub'd.
I hope you do more lens making in the future.
Can you reinforce your silicone molds when you create them? Add bamboo skewers or something that you leave in? It seems like a grid of them would be enough to sufficiently stabilize the mold.
Could PFF selfhealing wrap, vinyl war, latex or pof shrinkwrap work with epoxy as a release layer or those are too rough/sticky?
I wonder if burnishing graphite powder onto the lens surfaces would be sufficient as a mold release? Would be much more accessible as most people don't have a sputtering setup.
how do you think it won't affect the surface finish?
For a quick and dirty mold release, electroboom taught me to use liquid soap. I have tried it once, it worked.
Could you use thermal shock as a mould release? eg put the glass/silicone in the freezer, then pour warm water on the silicone, assuming it didn't pop off already during the freezing process?
While not ideal for several applications, I wonder if Fresnel lenses would yield a more consistent result given a more uniform thickness? This is a cool project!
As a mould release for silicone i can recomend hard car wax. Very simple but effective.
Carnauba wax, often used with polyester resin molds. Also found in some wood floor waxes of days gone by. I was scanning these posts for some mention of this. Good one!
Absolutely awesome research! Thank you very much for sharing, i would be very interested in the mirror project as well! Keep up the high quality experiments! Not very common on youtube
for those of us without sputter capabilities, have you looked at simple electroless silver deposition? This is the second video I've watched on your channel.... time to subscribe! :)
I haven't tried, but I suspect a chemical silver depositon would work great. I believe electroless and tollens both deposit fairly uniform, thin coatings so I would expect it to work equally well!
@@BreakingTaps one thing... the thickness will be single layer..... but if you electroform on top... say with copper - things will be a much different (and better) story! :)
I guess you can avoid the silicon moulding step and create your own mould by sticking some kind stretchy plastic film (like food wrap) over a container. Then introduce partial vacuum into the container. As a result you will get a concave plastic mould with a smooth surface. And the curvature of the mould can be controlled by controlling the pressure inside the container. With two of these you can get a whole mould in which you can inject the epoxy (if aligned correctly) . You can use small to medium quantity of epoxy in this short of mould as if you use a big amount of epoxy the shape of the plastic film might get distorted due to it's weight. And I assume the plastic should also come out easily. It's worth giving a try.
I'm so jealous of you on so many levels!!!
Thumbs up from Montréal!
For a backer material for silicon molds, 3 mm (1/8") MDF is very stiff and relatively inexpensive. Would probably work well up to a 6 to 8" diameter lens.
Fantastic video- super interesting!
Off course you can we used to do it all the time we need to put samples in epoxy for the microscope , we polished them to perfection with diamond paste
Lapping something flat is a lot easier than trying to grind and polish a 3D profile (even simple ones like spherical profiles). Not saying it's impossible, just that it's considerably harder than with glass 🙂
Can you make multiple shapes of lenses with different curvatures on each side, by having the mold sideways and using different molds for capping the other side instead of having the top flat surface be one of the surfaces of the lens?
I think that would be possible! You'd essentially build a 4-part mold instead of a 2-part mold, and you'll get a bit of a layer line between top/bottom, but I don't see any reason why it wouldn't work!
Edit: oh I misunderstood, yeah what you said should be doable too! If you don't mind the layer line, molding top and bottom instead of back/front should work fine, and give you a chance to use different curvatures
Instant like, have been looking into this for a while, comment before watching the full video. Interesting would be an "easy" way to create custom lenses instead of recreating already available lenses, mainly lens arrays, couldn't really find any 3d models or software for making those
(11:45) this is why I thought of using silicon carbide grit added to silicon rubber for tires would make an incredibly long wearing tire, as the SiC would be protruding making the contact with road surfaces while the rubber could squish down between these grits, and you would then be riding on nearly as hard as diamond needle points that would give refined surface friction, as well as removing any smoothing that has happened from regular tires polishing a road surface and making it too slick so other tires would get better grip while driving too.
run this layer of SiC grit layer deep enough and you could get a tire that lasts millions of miles instead of thousands or tens of thousands of miles LOL.
Rather tough on the roads, though. I really would form a physical rut to match the functional one in my home-to-work route. But If only you and I had these gritty tires, okay. The wear would be negligible and the grip, prodigious. Unit cost of tires, also prodigious. Oh, well ... . Still, I like your thinking.
@@gemanscombe4985 yeah this is kinda why packing higher grit in around the lower grit so that normal driving would not cause such an aggressive action, unless its needed by needing to apply more effort into rotation or when sliding so the coarser grit can be pushed down around causing a more aggressive gripping and some gritting like on rough ice or something, thus instead of wearing a rut so much as a polished section of the road lol.
@@gemanscombe4985 also how do you see ruts being cut when I see people who wander all over the road so much that the road would get evenly worn down along with half a foot over the other side of those white lines on the sides or worse (saw a cop doing this for nearly 4 miles where they had drifted to the side almost to the grooved section to let you know, and were hanging out there one tire completely over the white line by nearly a foot, before they seemed to have noticed and corrected to be in between the lines
@@ThomasAndersonbsf Yup, cops can be the worst b/c they give each other breaks we would never get. "Professional courtesy", they call it. Anyway, I'd expect ruts b/c the majority of contact is made over 2 foot-wide bands that straddle the lane center, that center being demonstrated by the oil drips discoloring that part of the pavement. Certain curves and braking zones would really wear as each car's tires applied lateral and longitudinal force repeatedly and predictably. Be outstanding for winter tires and less destructive than studs.
when you were talking about the mold release. do you actually need to make a mold with a glass? its probably easier with glass but all you should need a smooth curved surface. I guess its probably easier with glass
Yep, can be any material! The hard part is getting the optical surface, and the easiest/cheapest way I could think to do it was with lenses which by definition have that optical surface. I wasn't sure how to get it any other way (cheaply, that is) :(
Is it possible to make eye lenses from epoxy without getting distortion. Would it have to be very thin. I just want a clear see through surface.