Embedding of taggants in the vat photo-polymerisation additive manufacturing process for anti-counterfeiting measures

The Additive Manufacturing (AM) industry has grown significantly and attracted global attention. The unique nature of AM, that it can manufacture components from CAD data, made it vulnerable to fraudulent and counterfeit activities. With scanning and reverse engineering technologies advancing, existing authentication methods (such as embedded Quick Response code) become easy to detect and reproduce, and therefore unreliable. This article investigates a novel authenticating method for vat photo-polymerisation process with a double-lock system introduced. Both physical hash (the taggants) and digital hash (generated by X-Ray computed tomography scan) were embedded into each component. A number of digital hashing methods were proposed, including using a combination of the taggant spatial coordinates, colour code and quadrat count, which are impossible to reproduce. Using a 100µm layer thickness, the χ ² value of the distribution can also be used as the digital hash. This study also indicated the embedded physical taggants had no effect on the thermal properties of the parts, and had minimal impact on the mechanical strength, with reductions of 3.1 ± 0.5%, 3.9 ± 0.5% and 1.1 ± 0.5% in UTS at room temperature for the 100, 50 and 25 µm layer thicknesses observed. The UTS for all samples decreased with increasing temperature The existence of the taggant did not affect the UTS within statistically significant levels, except for those tested at 23 ^o C and 180°C with 3.1 ± 0.5% and 17 ± 2% observed variation in UTS between samples with and without taggants.