this post was submitted on 16 Jul 2025
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You'd also have to use the same slicer settings, similar room conditions, make sure that you have the same filament roll (assuming it's an FDM printer), make sure that nothing hardware wise was tweaked (eg. fixing belt tension), make sure nothing software wise was tweaked (it's nuts how much difference temp can make), make sure nothing firmware wise was tweaked, and the nozzle cant have had too many prints between the suspicious one and now (or like half of a glow in the dark or carbon fiber filled print).
Edit: and same print orientation, just turning the part direction in the slicer causes different artifacts, in extreme cases I've seen a part facing one way fail, but a quarter turn right or left prints flawlessly.
It's also nuts how much difference eccentric nuts can make.
Both the ones for adjustment, and the operator.
Also the ones who think this is something with even tiny chance of being viable in court anytime soon or will persist as an effective crimebuster for any notable amount of time if they do.
The above comments have already covered many possible variations complicating things, due to the settings and positions of how the machine was used to 3d print something. The article claims 3d printing tech has nozzles that have unique signatures. They would (or at least should) need to make sure it is actually unique by cross checking with other nozzles too. Lots of them really, just to make sure.
That might require finding multiple nozzles made in the same batch as the murder weapon, preferably unused, so they could attempt to recreate the crime version, to rule it out. It might be a nozzle manufacturer causing these imperfections where each batch of 10,000 nozzles is made in an extrusion plant or injection mold or done like solder ball grid array or pipefitters and play-doh (i honestly have no idea how they are made lol) and it turns out every nozzle in the first row has the same 'fingerprint' that warps the same way with use.
As technology progresses, parts should (but these days, idk) be made with more durable materials, with greater precision, capable of smaller scales or higher complexity and these unique signatures disappear for any easily detectable method. That's just the nozzles. In theory, that can apply to many if not all the parts.
I mean, Fabs for CPU are currently producing chips at what, 3 nanometers now? I just learned about electron-beam lithography too. The 3d printed smoking gun fingerprinting will be an anacronism before it's a specialization, in my opinion.
Just a note on how nozzles are made, they are machined brass usually. They can wear pretty significantly over their lifespan too, especially if you run harsh materials (glow in the dark is harsh enough that a brass nozzle might not last a single print).
There are hardened steel nozzles, but even those are a wear item, they just wear slowly. As I said somewhere else, it's like trying to chase down a ransom note by analyzing the shape of the lead of a pencil that may have been used to write it. Just using it changes the properties.
That analogy with the pencil is great! Thanks for the info.