The Lowest-Effort Way Yet To Make 3D Printed Lenses Clear

This technique shared by [Andy Kong] is for 3D printed lenses, but would probably be worth a shot for any resin prints that need to be made nice and clear. The link to his post on X is here, but we’ll summarize below.

It’s entirely possible to print lenses on a resin printer, but some amount of polishing is inevitable because an SLA print still has layer lines, however small. We have seen ways to minimize the work involved to get a usable lens, but when it comes right down to it the printing process creates tiny (but inevitable) surface imperfections that have to be dealt with, one way or another.

3D-printed lenses fresh (and wet) from the printer look clear, but have tiny surface imperfections that must be dealt with.

One technique involves applying a thin layer of liquid resin to the surface of the printed lens, then curing it. This isn’t a complete solution because getting an even distribution of resin over the surface can be a challenge. [Andy] has refined this technique to make it ridiculously simple, and here’s how it works.

After printing the lens, place a drop of liquid resin on the lens surface and stretch some cling wrap over the lens. The cling wrap conforms to the shape and curve of the lens while trapping a super thin layer of liquid resin between the cling wrap film and the lens surface. One then cures the resin while holding the cling film taut. After curing, [Andy] says the film peels right off, leaving an ultra-smooth surface behind. No tedious polishing required!

But what about the flat back of the lens? [Andy] suggests that instead of using cling film (which is better at conforming to a curved surface) simply use a drop of resin in a similar way to bond the flat side of the lens to a smooth piece of glass. Or bond the backs of two lenses together to make a duplex lens. This technique opens quite a few possibilities!

Even if one isn’t 3D printing optical lenses, we suspect this technique might be applicable to making crystal-clear 3D prints with a little less effort than would otherwise be needed.

Keep it in mind, and if you find success (or failure!) let us know on the tips line because we absolutely want to hear about it.

30 thoughts on “The Lowest-Effort Way Yet To Make 3D Printed Lenses Clear

    1. I was wondering about simply putting some of the liquid on the cling film and twisting it to make a clear ball or perhaps loosely stretching the film over a ring and adding the liquid, letting the weight of the liquid form the lens shape, the back should be nice and flat by default as long as the ring is level.

      1. I was thinking spin coating while reading the article as a way to do a convex shape, but I think you’re on to something when it comes to forming a parabolic mirror without needing to start with a print at all.

    1. I’d be curious how that will need to be adapted to concave or convex surfaces: ‘spin coating’ is absolutely a thing for applying thin films to flat surfaces(and, given that the semiconductor guys use it for applying resists for photolithography), accuracy and repeatability must be pretty decent.

  1. Ironically the reason cling wrap works for this is for the same reason it doesn’t work so well for keeping food fresh anymore. Specifically, the fact that they switched to polyethylene.

    1. The more the clear coat’s refractive index (when cured) differs from the print material’s, the more the “halo distortions” will be apparent in your finished lens. (Where you have a thicker toroid of clear coat in the corners of the steps in the print.)

  2. Oh my god that’s simultaneously genius and INCREDIBLY annoyingly simple, and clearly I’ve made lenses before and been here before to try and find a quick, simple and repeatable way to do this.

    oh my god.

  3. Has anyone building polymer lenses this way measured the scatter from tiny internal stresses and density variations? How does this compare with grinding a lens from bulk polymer?

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