3D Printed Electrical Fuses

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.

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• 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.

• Bench Test

  JohnsonFarms.us • 11/11/2025 at 23:13 • 0 comments

  So with the rig all setup I got to testing...and as suspected after the resistance test, they make a better resistor than a fuse.

  

  The hollow fuse allowed the most amperage through, but even at over 30 volts I barely got the led on the drill to turn on, let alone make the drill turn.
  

  Just for fun I tried hooking this up in line with my battery on my pickup while starting using some jumper cables, and still not enough to make a meaningful impact on the fuse, or start the pickup.
  

  I tested the resistance again after leaving it hooked as a ground short on the pickup battery, and while the fuse was not warm (but not cold either), the resistance had increased to just over 600 ohms. It seems that with enough voltage or duration, the fuse heats, and resistance increases with it. With a doubling of resistance within a temperature range I could not even feel, I can only imagine how high the resistance might get if truly heating up.

  Now the more interesting piece of this is that the conductive PLA does make for a decent resistor, and if you got your design dialed in well, you could be pretty consistent in the resistance. I could see easily printing resistors for LEDs, buzzers, and a number of other small projects.
  

  Video available at https://www.tiktok.com/t/ZTH3RtNxVDanW-ZAYRm/

• 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 we are already down this rabbit hole so lets keep going.

  

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