As car security systems become ever more advanced, thieves are targeting car parts instead — including alloy wheels.

One method to deter them is to use locking nuts (one on each wheel) that need a special key to loosen them. However, even these are vulnerable, leading Ford engineers to use 3-D printing technology to develop next-generation locking wheel nuts.

Together with additive-manufacturing specialist EOS, Ford has created locking nuts with contours that are based on the driver’s voice.

Like an iris scan or a fingerprint, a person’s voice can be used as a unique biometric identification.

Engineers record the driver’s voice for a minimum of one second, saying something like “I drive a Ford Mustang”, and use software to convert that singular sound wave into a physical printable pattern that is then turned into a ‘circle’ and used as the design for the locking nut’s indentation and key.

With the geometry in place, the nut and key are designed as one piece, then 3-D printed using acid- and corrosion-resistant stainless steel.

When finished, the nut and key are separated, with a small amount of grinding required to make them ready for use.

The design also includes second-level security features that prevent the nut from being cloned or copied.

The unevenly spaced ribs inside the nut and indentations that widen the deeper they go prevent a thief from making a wax imprint of the pattern, as the wax breaks when it is pulled from the nut.

If not using the driver’s voice to create the contours, the nuts could feature designs specific to a vehicle — such as the Mustang logo — or use the driver’s initials.

The design could also take inspiration from a driver’s interests — for example, by using the outline of a famous racetrack.

Raphael Koch, Ford Advanced Materials and Processes research engineer, said: “Some alloy wheels can cost thousands to replace, but these unique rim nuts will stop thieves in their tracks.

“Making wheels more secure and offering more product personalisation are further proof that 3-D printing is a game-changer for car production.”