Identifying Class and Individual Characteristics of Printer Marks on Additively Manufactured Firearm Components

The objectives of this proposal are: 1) to identify class, sub-class and individual characteristics of 3D printer toolmarks in the topography of additively manufactured parts and 2) to evaluate the feasibility of applying objective comparison methods to determine whether parts were made by the same type of 3D printer, or alternatively, a specific 3D printer.

Recent innovations in additive manufacturing, also known as 3D printing, are enabling consumers to manufacture complex 3D printed parts with little to no manufacturing experience. The current generation of consumer-level 3D printers are low cost and can produce parts with tight tolerances and improved strength, durability, and impact resistance.

Combining 3D printers with publicly available computer aided design (CAD) data files enables consumers to produce functional firearm parts. These can be used for illegal firearm modifications, or as components in non-serialized, privately made firearms, also known as "ghost guns". The proliferation of ghost guns represents a growing challenge to law enforcement and forensics. Ghost guns enable evading restrictions on the acquisition of firearms and circumvent gun tracing, a key tool for law enforcement to reduce firearm violence and trafficking.

The growing opportunities of 3D printed parts being used in criminal activities requires the development and characterization of forensic capabilities relevant to 3D printed parts and 3D printers. This proposal addresses a key capability of interest: the ability to determine whether 3D printed firearm parts used in a criminal activity were made by a particular 3D printer.

The first proposal component is a systematic study of 3D printing techniques and printers to identify possible class and sub-class characteristics in the geometry of printed parts. Such characteristics can be used to restrict the population of printers that could have made a particular part. The second component addresses the feasibility of identifying and comparing individual features on 3D printed parts to determine whether parts were made by a particular 3D printer. This activity will focus on printers that manufacture parts by depositing lines of polymer, so called Fused Deposition Modeling (FDM) printers, that are by far the most popular consumer-level printers. Experiments will be conducted for a variety of printer models, build plates, nozzles, and process parameters. Topography measurements will be conducted using state-of-the-art 3D measurement techniques. Methods developed for the objective comparison of firearm toolmarks will be modified and evaluated for their ability to address the unique challenges of additively manufactured parts.