Wouldn’t it be handy to just print a fuse? I thought so. Is conductive PLA the material to do it with? Probably not, but I tried anyway—and what I discovered along the way turned out to be more useful than the original goal.
The Experiment
For this project, I set out to create 5x20mm barrel fuses using 3D printing with conductive filament from Protopasta. The concept was straightforward: generate enough heat via resistance to melt the PLA and break the connection when too much current flows through. Is it wise to melt plastic into your electronics? Probably not. Did that stop me? No.
From my previous experimentation with conductive PLA, I’d learned that this material actually makes for a better resistor than anything else. So I decided to crank up the power supply and see what happens.
The Testing
I printed several fuse designs and tested their resistance. The hollow 3x8mm design performed best at 300 ohms, while a 1x1x8mm square measured 1250 ohms. During bench testing with over 30 volts, even the most conductive design barely lit an LED on my drill. I even tried hooking one up to my truck battery while starting—still no meaningful impact on the fuse.
Interestingly, after leaving the fuse hooked as a ground short, I noticed the resistance had increased to over 600 ohms. The material heats up and resistance increases with it, doubling within a temperature range I could barely feel.
The Actual Useful Discovery
Here’s the kicker: the fuses make terrible fuses but excellent resistors. If you get your design dialed in well, you could be pretty consistent with the resistance values. I could easily see printing resistors for LEDs, buzzers, and other small projects instead of keeping a stock on the shelf.
Final Thoughts
The fuses could hypothetically work as fuses, but the practical voltage requirements make it unfeasible. However, discovering that conductive PLA makes a decent printable resistor? That’s the real win here.
Check out the full project on Hackaday.io for all the details, test data, and a video of the experiment in action.
