3D Printed Fiberoptic UV Flashlight for Curing Resin

When 3D printing with resin, it may become necessary to print them with some or all segments hollowed. Either to reduce stress or material requirements.

Such prints also require holes for the uncured interior resin to leave, as well as making it accessible for washing. Otherwise, the uncured interior resin has a high chance of generating fumes that will crack the print as they expand. These holes are often very small in diameter, making them inaccessible to most UV-curing lights. Even UV LEDs rarely fit into holes with a 2mm or less diameter.

To that end, I developed a basic UV flashlight that shines a LED light into a very fine fiberoptic cable, which can be used to transfer light even into very small holes. To make storage easier, the fiber optic cable is attachable to the flashlight by a clipping mechanism. And it has an (optional) multi-material logo just for flair.

This instructable guides you through the steps needed to construct your own flashlight (both multi-material and not). It does not however detail the design process for the flashlight. If you are interested in the iterative design for the flashlight, you can check out my blog.

The software for CAD development was Fusion 360 through a student license. I'm a student of Boston University

Materials you will need:

1. Material Filament. I used Overture Filament of Different Colors (I think their Orange looks especially spiffy).
2. 9 Volt Batteries (I bought this pack on Amazon).
3. 9 Volt Clip Connector (Amazon Link).
4. ON/OFF switch (Amazon Link)
5. UV Emitting LED (Amazon Link)
6. Heat Shrink Butt Splicers (Amazon Link)
7. 1.5 mm diameter Fiberoptic Cabling (Amazon Link)

Tools and Equipment you will need:

1. Metal pliers, maybe even a set of two.
2. A ruler for measurement.
3. A 3D FDM printer with at least a 10x10cm build plate (give or take). I used a Prusa MK3S.
4. A heat gun. Absence of one, a hot hairdryer will also work. In the absence of both, a lighter may suffice.
5. A razor blade, or a wire stripping tool.

Tools and Equipment you may want:

1. Sanding Tools (useful for smoothing down rough edges).
2. Wire Clippers for soldering.
3. An FDM printer capable of multi-material printing. I used a Prusa MMU2S attachment.
4. Plastic Scraping Tool (useful for removing prints)
5. A drill with a 3 mm diameter. In case your printer can't handle printing overhangs without warping (even with supports).
6. Masking tape
7. Super glue

The following are individual STL files used for printing the shell the flashlight will use to store the electronics as well as to slot on the fiber optic cable.

Regardless of single-material or multi-material printing, you will need:

1. Fiberoptic_Slot
2. Flashlight_Lid_A
3. Flashlight_Lid_B

If you want to play it safe and print with one type of material:

1. Flashlight_Single_Material

If you want to print the core with a multi-material logo:

1. All the files that begin with "Flashlight_Color"

I used PRUSA SLICER for my slicing needs, as it was the most compatible with my multi-material printer, but if you have a better slicer of choice, you should feel good about using the one you want.

I mostly used default printing settings, but the following may be noteworthy for those following my steps:

1. I used a 0.4mm print nozzle
2. The layer height was set to 0.15mm, prioritizing quality over speed
3. The prints are designed to be printed with removable supports provided by individual slicers.
4. Infill Density is set to 15%.
5. There was a 3 mm brim to prevent curling
6. Each STL file was oriented to need the least amount of support material. However, plate arrangement should be handled on a per-slicer basis.

I have an enclosure for my printer which I have an image for right here. Each 3D printer will be different, so my advice here is more general (and smaller).

• Applying Isopropyl alcohol can be good for adhesion.
• A plastic scraper is good for removing stuck prints.
• If your having trouble printing multiple parts at a time, there is no shame in printing 1 STL file at a time.

Once printed and removed from the plate, you may need to do some sanding and scraping to remove any stuck brim or supports. It should preferably be nice in the hand and smooth to hold.

If the hole for the LED isn't large enough to fit it most of the way through, you can also use a drill to enlarge the hole a bit. Use the razor blade to scrape out support materials in the areas that are tight.

The tolerances for the On/Off switch should be fine without further work, but this could benefit from sanding in case it doesn't.

It's also a good time to check that the parts all fit together. The smaller lid should click into place, and then the larger lid should be attached afterward

The LEDs, On-Off Switch, and battery packs should come with excess wiring. For those unexperienced Il provide some general guidance to make sure the end result works. I have a wire holder for soldering which makes the process significantly easier, but it should be doable even without them.

Before modifying any of the wires, you can check to see if any of the components work individually, by touching the tips of the wires together.

• Take the LED and the battery pack (with an attached battery), and just the exposed wires together to make sure the light works.
• The black wires should be touching each other
• Colored wires (red or purple) should be touching each other
• Assuming you did it right, you should get a light.
• You can also test to make sure the process works with the On-Off Switch
• Tape one of the LEDs and Battery packs wires together temporarily so they remain in place
• Connect the On-Off switch's wires to the other two in a triangular configuration.
• The On-Off Switch's wires can be connected to any color wiring as long as the LED to Battery packs connection still matches colors.
• Assuming you did this right, turning the switch on and off should in turn control the LED.

After you are sure the lights work, you should pare down the wiring, as it's too long normally. Each wire of each component should be pared down to roughly 20 mm or around 0.5 inches in length (use the razorblade).

You will need to strip around 5 mm of wiring from the tips of the components. If you have a wire stripper, use them. As I did not, I detail how I did it without them:

I took the razorblade and I made 5 mm cuts into the middle of each wire. Then I scraped away the protective cabling, and then lastly twisted the exposed cabling back into bunches.careful with the fingers.

Make sure to avoid making diagonal cuts as that can cut away at the internal wiring.

Once you tested that the shortened wires can successfully generate a light, its time to connect them together.

Slip a butt splicer on one end of a wire, and then slip in a connecting wire on the other end. I used a wire clip to hold them together, but some masking tape can be a worthwhile substitute.

Apply a heat gun, or hair dryer until the butt splice becomes visibly softer, and you will see it gripping to the wires. After roughly 30 seconds, it should be left to cool for roughly 1 minute.

Repeat this process for the other 3 wires.

Afterward, to help with contact, you can use pliers on the cooled butt splicers to have them clamp tighter on the wiring.

The wiring should all primarily fit through the On-Off switch socket.

You may choose to glue the LED light in place, but it should hold through pressure alone.

The battery clip should be inserted as shown.

In case the splice plugs make it difficult to fit in completely, you can use calipers to bend them at an angle.

If all goes well, you should be done with most of the complex aspects of production.

Lastly, all thats left is to fit the fiber optic cable into the clip. You can generally achieve this with a slight amount of force. If the hole is too tight, you can loosen it with a 1 mm drill.

The clip initially will be hard to remove once attached in place in front of the flashlight, but after attaching it and removing it a couple of times, it should loosen and keep it in place without being too tight.

Viola, it is complete.