Optical Fabrication — Part 2: Making Lenses Using Silicone Molding
Are you curious as to how lenses are made and if it’s possible to make them yourself? Although there are different processes for making lenses, in this article we will be exploring making lenses using resin and silicone molds. We will also cover the challenges you might face when making lenses through molding and some of the different applications for casted lenses.
If you feel inspired by this article and decide to do it yourself, we hope you like to get your hands dirty because anything involving casting with resin is a bit messy. With that in mind, be sure that you are equipped with some gloves and goggles before starting this DIY lens-making process.
Before performing these steps, be sure you have your mold ready to go and a design for your lens. If you need some assistance on making a mold, take a look at our article entitled, The Complete Guide to DIY Molding & Resin Casting.
Now that you have everything you need to make a lens through silicone molding successfully, let’s get started.
Step 1: Clean the Mold
Cleaning the mold should be the first step when casting any resin, especially a lens. It is that much more critical when making a lens because every imperfection, such as dust or debris, will be magnified. With that said, the lens needs to be flawless.
Step 2: Mixing Your Resin
Make sure that you mix both parts of the resin properly. This means ensuring that the correct amount of each part of the resin is being used. (Generally speaking, it is divided into 2: Part A and Part B).
Step 3: Vacuum Chamber
This next step is relatively simple; put the mixture of Part A and Part B in a vacuum chamber to eliminate as many bubbles as possible. The amount of time you need to leave it in the vacuum chamber will depend on the resin type. The resin that we used takes roughly 20 minutes before it starts curing, so there was no rush to take the resin out of the vacuum chamber.
Step 4: Pouring
Once the mix is out of the chamber, carefully pour the resin into the mold, avoiding adding any bubbles.
Step 5: Pressure Chamber
Once the resin is in the mold, put the mold into a pressure chamber and wait the appropriate amount of time that your resin takes to cure.
Step 6: Demolding
This last step is fairly self-explanatory; take the lens out of the mold and make sure the lens is optimal. If something went wrong, start again from Step 1.
Challenges
With most resin casting projects, the main issue is avoiding bubbles. As stated above, lenses need to be perfect, or else they will magnify every minor imperfection and distort any projection that goes through the lens.
Another potential problem when casting resin is that parts may deform or not form at all. For example, here are some images of how a lens can look when something goes wrong:
Solutions
If we want to solve the bubble problem, it is going to require out-of-the-box thinking. Since injecting resin from the top of the mold causes bubbles, you will need to inject it from the bottom.
With that said, here are the steps to inject the resin from the bottom of the mold:
- Make a hole in the bottom of the mold, ensuring you can fit one end of a rubber tube into the hole.
- Then insert a syringe that will be used to inject the resin into the mold.
- Put a straw on top of the mold (where the resin will be injected) to add more resin to the mold. This way, when the mold is in the pressure chamber, when and if the bubbles shrink, they will pull resin from above to fill the space where they used to be.
What are the Benefits of Making Lenses Using Silicone Molds?
Casting lenses through silicone molding is not the easiest method, but it is a reasonably inexpensive way to prototype lenses before ordering already formed blanks from a reputable supplier or manufacturer.
What Lens Applications Are There?
Silicone molded optics target a wide array of markets, from the medical field to film/photography, virtual reality (VR), and even toys. This optical fabrication process targets most audiences that need lenses unless the end product needs tiny, precise lenses. In that case, using the single-point diamond turning (SPDT) machines is the way to go, which we covered in a previous blog post.
Conclusion
Now that you have a perfectly casted lens, assuming that the steps went according to plan, it is time to apply it! You can refer to the applications mentioned above, or you can use your imagination to create something entirely new.
If your lens isn’t perfect, that’s okay too. Sometimes it takes a few tries to get it right. That is the beauty of silicone molds, as well. You can recast until you achieve perfection using the same mold. The saying is true; practice really does make perfect!
If you need assistance with any stage of the optical fabrication process, whether that be design, prototyping, or manufacturing, Jaycon is here to help.
Part 3 of this Optical Fabrication series is out now! Read about how to make lenses through 3D printing to venture into the optical expert you were bound to be.
