A new study from researchers at Curtin University in Australia is exploring the possibility that 3D-printed “ghost guns” could be traced through chemical analysis. Collaborating with ChemCentre, a statutory forensic laboratory in Western Australia, the scientists are attempting to find a way for law enforcement to link illegal 3D printed parts to the criminals who produced them.
However, using forensics to trace the chemical properties of PLA or ABS could be worthless information. An astounding amount of filament is produced by only a handful of incredibly large Chinese factories, which then “white-label” their products for others to sell as their own. Brands hate to admit it, but a lot of popular plastic flows through factories owned by eSun, Sunlu, and Polymaker. American companies like ProtoPasta and Printed Solid look like boutique manufacturers when compared to the two million spools a month that Sunlu can produce.
Even the researchers were forced to admit that many of their samples shared the same chemical properties, concluding that “the limited variability among different vendors may indicate that they share the same supplier or that there are limited suppliers for the Australian market.”
Normally, forensics can trace a firearm back to the shooter by studying the ballistics, the “fingerprints” mechanically left on a bullet after it is fired from a gun. Bullets are etched by the rifling, or the spiral grooves, within the barrel of a firearm, while the firing pin can leave distinct tool marks. These microscopic scratches are unique to each weapon.
However, a fully 3D printed gun could be made of plastic that degrades with each shot, if it even survives the firing process. There’s also the obvious issue that ghost guns, whether 3D printed or obtained through more mundane methods, lack the serial numbers of legally purchased weapons.
This new study hopes to find traces of polymer that could act as a chemical “fingerprint” to ID a 3D printed part. The researchers found that when a 3D printed firearm is discharged, it could leave behind tiny fragments and particles of plastic at the crime scene or embedded in the ammunition itself.
The team gathered 67 samples of both raw and printed filament that could be purchased locally in Australia. While some samples of filament were donated or purchased for the study, others were seized by the Western Australia Police Force. They even included PLA color swatches that ship free with a new Bambu Lab printer. Notably, the scientists did not print any of the samples themselves, so that the type of printer used and the conditions of the printing environment remained unknown for the study.
The samples were largely PLA, with some PETG and ABS. All the printed samples were either Bambu filament swatches or 19mm discs printed by volunteers.
The researchers scraped the swatches and raw filament strands with a scalpel for the study. These shavings were analyzed with an ATR-FTIR spectrometer. The results revealed that the scientific equipment could not distinguish between brands, colors, or whether the filament was raw or printed.
They also scientifically discovered a fact well known in the 3D printing community: that filament is often a blend of unlisted, and rather surprising, materials. A sample of PLA-Flex from the now-defunct Australian company, 3D Fillies, was shown to consist of PLA and PETG. The researchers also studied Rainbow and Tri-Color PLA, which are the least durable materials for practical prints, let alone weapons.
Researchers were flummoxed by the presence of ABS in the PLA sample, concluding that the nozzle may have been contaminated with one material before printing the other. This caused them to conclude that the first layer of a print is unreliable for scientific study.
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