Chemical ghost signatures protect DED 3D printed parts from counterfeitting

IP protection is one concern that could stilt the growth of additive manufacturing for sensitive applications in high value industries such as aerospace, automotive and defence.

Protection methods under investigation include embedding quantum dot signatures, microstructural manipulation and advanced encryption of the digital design files.

The solution proposed by Dr. Sharon Flank et al. from InfraTrac, is to add spectral signatures to the 3D printed parts that can only be read via x-ray. This technique is more cost effective than some of the other methods in experimentation as it can be conducted using off-the-shelf devices.

The latest research into the method has been conducted in collaboration with the Penn State’s Center for Innovative Materials Processing (CIMP) and results have been published in the 3D Printing and Additive Manufacturing journal.

Leaving metallic fingerprints

The most effective 3D printing method for chemical tagging of parts is directed energy deposition (DED) as it allows the use of multiple metals. In InfraTrac’s study, an Optomec M7 LENS system is used to 3D print titanium alloy samples. Chemical taggants are added to the parts at different depths, and scanned using x-ray fluorescence (XRF) spectroscopy analysis in lab conditions.

(a) Illustration of layers in a smaple without taggant. (b) center and (c) off center placing of the chemical taggant. Image via 3D Printing and Additive Manufacturing journal.(a) Illustration of layers in a smaple without taggant. (b) center and (c) off center placing of the chemical taggant. Image via 3D Printing and Additive Manufacturing journal.DED 3D printed titanium samples with varying taggant depths used in the InfraTrac study. Photo via 3D Printing and Additive Manufacturing journal.DED 3D printed titanium samples with varying taggant depths used in the InfraTrac study. Photo via 3D Printing and Additive Manufacturing journal.

An advanced game of Battleship

Results show that taggants on the surface of parts, though invisible to the naked eye, can easily be detected by XRF. 250 μm deep into the titanium sample however, the taggant becomes harder to differentiate.

Varying stages of taggant presence. Using (a) as a reference point with less taggant content, (b) and (c) clearly show the chemical presence. Image via 3D Printing and Additive Manufacturing journal.Varying stages of taggant presence. Using (a) as a reference point with less taggant content, (b) and (c) clearly show the chemical presence. Image via 3D Printing and Additive Manufacturing journal.

A number of possible improvements are identified by the team to enhance the “smearing” effect in titanium, as a soft metal, that may cause poor clarity. As an example, Flank et al. suggest that “machining/grinding with sufficient lubrication or the use of an etchant, can reduce the effect of smearing.”

The researchers state that “These results are encouraging.”

“Preliminary results suggest hat not only can a taggant mix be detected but also can be hidden in a specific predetermined position, as in a game of Battleship.”

“Moreover, it can be quantitated as well so that a counterfeiter attempting to replicate the fingerprint would have to know about it, find exactly which spot it is in, and replicate its depth and composition correctly, along with matching the composition of
the matrix materials.”

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Featured image shows DED in Optomec’s LENS technology as used in the InfraTrac study. Screengrab via Optmec on YouTube

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