This project makes a gadget for a pair of safety goggles. The front half of the gadget can be rotated, allowing light to pass through a pair of of polarized lenses. By rotating the lenses against each other, you can adjust the amount of darkness the goggles provide.
After the kids and I saw a 3-D movie, we kept the polarized 3-D glasses after the show, and playing with the lenses inspired this project.
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Step 1: What You Will Need
I used steel Screw Ring Goggles from www.gentlemansemporium.com, (disclosure: I work there!) but they are available elsewhere. If you use a different type of goggle, you will probably need to adjust the design to account for the thread size.
Clear 50mm cover lenses
Also from www.gentlemansemporium.com, but available elsewhere. 50mm diameter is a relatively standard size for safety and welding goggle lenses. You will need at least four cover lenses.
Thin polarized sheets
I bought mine on www.amazon.com, but they're available elsewhere. The sheets I purchased were thin plastic, laminated with a linear polarized film. They were 80mm square, but you'll need sheets that are at least 50mm square to make the polarized lenses from.
3-D printed lens kit.
You'll need to print the kit twice, one for each eye.
Get the .stl file linked below, or get it on thingverse.com.
If you need to tweak the design, you can get it on tinkercad
Step 2: Cut the Polarized Sheets Into Circular Lenses
For each eye, we will want two circular polarized lenses. Because the cover lenses are 50MM diameter, the circular polarized lenses need to be just a hair smaller than 50mm
The sheets I purchased were 80mm square, which was just enough space to cut two lenses from each sheet. Here's what I did:
- Cut the sheets diagonally.
- Using the cover lenses as a pattern, draw a 50mm circle in pencil in the corner of each piece of material
- Cut out the circles with scissors.
For now, you can leave the circles rough, and slightly oversized. We will trim them down later for final assembly.
You will need four circles.
Step 3: Print the Lens Kits With Your 3-D Printer
I used my Robo 3-D printer with PLA. Suggest you print on high quality to ensure fine details come out well.
Step 4: Check the Fit of the 3-D Parts
For now, we'll just check the fit of the 3-D parts and the cover lenses
The 3-D file prints 3 objects, displayed in the design as Red, Orange and Yellow.
- The interior diameter of yellow is slightly larger than 50mm. Check that you can snap the cover lens into yellow without forcing it.
- Yellow and Orange should snap together snugly, but without being forced. Take Yellow and Orange back apart.
- Note that Red has threads on the inside. These will attach red to the front of the screw ring goggles. Check that the threads align, but do not screw it on tightly yet. Remove Red from the goggles.
Step 5: Ensure That the Parts Snap Together and Can Rotate Freely.
Note that Red has a circular channel, indicated with a dotted green line in the photo above.
The back of Orange is slightly flared, and this flared edge needs to snap down into the channel in Red and rotate freely without falling out.
Check the fit of Orange to Red, and ensure that Orange can be rotated freely without too much friction. Orange should be able to snap together with some light pressure, and Orange should be retained in place without any light leaking through.
The fit between Orange and Red is the most important of the model. When printing mine, I had some issues of "elephant's foot" which led to some excess flash on the bottom I needed to trim to make the parts work.
Step 6: Trim the Polarized Lenses to Slightly Smaller Than 50mm
For the shading effect to work properly, it is very important that the polarized lenses are completely flat and parallel to one another. We need to trim the lenses to slightly smaller than 50mm diameter so they can sit inside of the goggle body without being forced.
Try to keep their circular shape, and just trim a very small amount of material around the edge.
Dry fit the lenses into the body of the goggles and the cavity in Yellow until they can sit flat. The cover lenses are meant to just provide physical support for the polarized lenses.
Be careful to not over-trim the lenses, as they still need to be held in place by the gadget which has thin walls.
Step 7: Determine the Polarized Lens Alignment
Determine the sequence of polarized lenses and the cover lenses to achieve the variable shading effect.
Hold the two lenses up to one another and rotate one of them until you can see it darken and lighten as in the animation at the beginning of the Instructable. If it doesn't work properly, flip one of the lenses and try again.
Once you know how the polarized lenses should be aligned, you need to do the same for the cover lenses.
The clear cover lenses are meant solely to provide rigidity to the flexible polarized lenses, but they can also interfere with the shading effect. Hold one cover lens and one polarized lens in each hand, and look through all four lenses, rotating one hand. When it's correct, you should see the shading effect.
The sequence that I used was cover lens / polarized lens / polarized lens / cover lens. You will need to play with the sequence of the lenses until you get a combination which works in your situation.
Once you determine the correct sequence, set the lenses aside, keeping track of the sequence and orientation of the lenses.
Step 8: Final Assembly, Part 1
Unscrew the cover from the goggles. Put a polarized lens and a cover lens into the cover, and reattach to the front of the goggles.
Put the other two lenses into Yellow, and snap Orange into Yellow. This creates the rotating OY assembly.
Look through the goggle, holding OY in front of it, and rotate to confirm that the shading effect works correctly. If not, correct.
Step 9: Final Assembly, Part 2
Screw Red onto the exterior of the goggle cover. It should fit tightly. Tighten it until it holds firmly and where the notch in the front of Red is facing up. This reduces the chance that the rotating piece will fall out.
Snap the OY assembly down into the notch in Red and confirm that it can rotate smoothly. Look through the goggle and ensure that the shading effect is working properly.
Repeat these steps for the other side of the goggles.
My prototype prints were in red, but this allowed some red-tinted light to pass through the sides of the lens, because the thin walls of the PLA are not fully opaque.
My next version I will print in black PLA.