3D Printed Electrical Fuses

Description

For this project, I am looking to 3d print 5x20mm barrel fuses with conductive filament, the kind you find in small electronics and older automotive applications. I will use a bench top power supply, fuse holder, thermometer, multi-meter, and conductive filament to test a handful of potential designs. The goal is to generate enough heat via resistance to melt the PLA and break the connection. Is it wise to melt plastic into your electronics? Probably not. Will that stop us? No.

Details

Wouldn't it be handy to just print a fuse? I think so. Is conductive PLA the material to do it with? Probably not, but let's try anyway.

For this project, I am looking to create 5x20mm barrel fuses, the kind you find in small electronics and older automotive applications. I will use conductive filament from Protopasta, fuse holder from Digikey, bench top power supply, thermometer, and multi-meter to test a handful of potential designs.

The goal is to generate enough heat via resistance to melt the PLA and break the connection. Is it wise to melt plastic into your electronics? Probably not. Will that stop us? No.

In my previous experimentation (failed and successful) with the conductive PLA, I found that this material makes for a better resistor than anything, so let's crank up the amperage and see what happens.

Check the logs for updates and follow along.

Files

fuseholder.stl

Bench test stand for the Digikey 486-1988-ND Fuse Holder

Standard Tesselated Geometry - 244.61 kB - 10/16/2025 at 01:39

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5x20fuse-1x1square.stl

5x20mm fuse with 1x1x8mm square center

Standard Tesselated Geometry - 24.89 kB - 10/16/2025 at 02:39

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5x20fuse-2x2square.stl

5x20mm fuse with 2x2x8mm square center

Standard Tesselated Geometry - 24.50 kB - 10/16/2025 at 02:39

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5x20fuse-3x3square.stl

5x20mm fuse with 3x3 square center

Standard Tesselated Geometry - 24.89 kB - 10/16/2025 at 02:39

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5x20fuse-sidehole.stl

5x20mm fuse with 3mm hole perpendicular through center

Standard Tesselated Geometry - 44.71 kB - 10/16/2025 at 02:39

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Components

1 × Conductive Filament Protopasta https://proto-pasta.com/products/conductive-pla?_pos=1&_fid=7dc416278&_ss=c

1 × Fuse Holder Digikey 486-1988-ND https://www.digikey.com/en/products/detail/schurter-inc/0031-5001/640403

1 × 3D Printed Stand Bench test stand for the fuse holder, see files.

1 × M3 Bolt A short M3 bolt to attach fuse holder to stand.

Project Logs

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Resistive Test Results
JohnsonFarms.us • 10/16/2025 at 03:57 • 0 comments
So the first round of fuses are printed and a quick round of resistance measured with each.

The printing was successful, but done "with brim" to help keep them in place. That said, I am not sure that was necessary, it had been a while since I had used the conductive PLA and I forgot how great the bed adhesion is, it sticks well, really well. So the next round will probably be without brim since the thinner fuses are difficult to separate from the brim without breaking, that and they get a weird flat spot from the brim.

Another note on printing, the fuses need printed horizontal, the conductivity between layers is not as good as within layers, so unless greater resistance is needed stick with horizontal.

For the test each fuse was pulled in and out of the holder 3 times and also wiggled/rotated while it was in it. The results are the average and/or most consistent reading.

All of the following are the 5x20mm barrel fuses, with a descriptor and ohm of the "fuse" portion.
- 1x1x8mm square: 1250 ohms
- 2x2x8mm square: 500 ohms
- 3x3x8mm square: 350 ohms
- 3x8mm hollow: 300 ohms
- 3mm perpendicular hole: 300 ohms
Obviously these are quite high for a fuse, but where else are we going to get that heat to melt our PLA.

View project log

Discussions

crun wrote 10/20/2025 at 05:00

The side hole version could be constructively packed with potassium chlorate or nitrate powder to more reliably clear the circuit. (Potassium permanganate would also offer a handy wireless indicator function).

21st century man might choose sodium bicarbonate.

Are you sure? yes | no

JohnsonFarms.us wrote 10/21/2025 at 07:15

or even call it an “audible warning”, it would make “blowing” the fuse make more sense 🤣

Are you sure? yes | no

3D Printed Electrical Fuses

Description

Details